linux-dey-6.1: add RT functionality to CCiMX93
This commit adds RT functionality to the CCiMX93 platform. The patches have been extracted from the NXP real time edge BSP and include the maineline RT patches and the NXP RT driver patches and RT Kernel defconfig changes. https://onedigi.atlassian.net/browse/DEL-8881 Signed-off-by: Mike Engel <Mike.Engel@digi.com>
This commit is contained in:
Mike Engel
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e2caf16da4
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From 5a9357f51ccd92dd11f188a14edf4b92ba1543ee Mon Sep 17 00:00:00 2001
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From: Mike Engel <Mike.Engel@digi.com>
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Date: Fri, 23 Feb 2024 10:12:23 +0100
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Subject: [PATCH 02/10] RT: add RT localversion
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Signed-off-by: Mike Engel <Mike.Engel@digi.com>
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---
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localversion-rt | 1 +
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1 file changed, 1 insertion(+)
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create mode 100644 localversion-rt
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diff --git a/localversion-rt b/localversion-rt
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new file mode 100644
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index 000000000000..6e44e540b927
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--- /dev/null
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+++ b/localversion-rt
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@@ -0,0 +1 @@
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+-rt12
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--
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2.34.1
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@ -0,0 +1,581 @@
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From e418c26b14e840304aa6e00ef847ec41ac0b995e Mon Sep 17 00:00:00 2001
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From: Mike Engel <Mike.Engel@digi.com>
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Date: Fri, 23 Feb 2024 12:28:42 +0100
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Subject: [PATCH 04/10] Documentation: add NXP RT support
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Signed-off-by: Mike Engel <Mike.Engel@digi.com>
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---
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.../mailbox/generic-software-mbox.yaml | 65 +++
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.../devicetree/bindings/net/fsl,fec.yaml | 24 ++
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.../devicetree/bindings/tty/rpmsg_tty.yaml | 67 ++++
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Documentation/printk-ringbuffer.txt | 377 ++++++++++++++++++
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4 files changed, 533 insertions(+)
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create mode 100644 Documentation/devicetree/bindings/mailbox/generic-software-mbox.yaml
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create mode 100644 Documentation/devicetree/bindings/tty/rpmsg_tty.yaml
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create mode 100644 Documentation/printk-ringbuffer.txt
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diff --git a/Documentation/devicetree/bindings/mailbox/generic-software-mbox.yaml b/Documentation/devicetree/bindings/mailbox/generic-software-mbox.yaml
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new file mode 100644
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index 000000000000..57c91ab2c80a
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--- /dev/null
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+++ b/Documentation/devicetree/bindings/mailbox/generic-software-mbox.yaml
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@@ -0,0 +1,65 @@
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+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
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+%YAML 1.2
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+---
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+$id: http://devicetree.org/schemas/mailbox/generic-software-mbox.yaml#
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+$schema: http://devicetree.org/meta-schemas/core.yaml#
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+
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+title: Generic Software Mailbox
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+
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+maintainers:
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+ - Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
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+
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+description: |
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+ The Generic Software Mailbox is a virtual device, which uses unused
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+ interrupt line to notify remote side and shared memory to emulate
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+ device MMIO registers.
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+
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+properties:
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+ compatible:
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+ oneOf:
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+ - const: fsl,generic-software-mbox
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+ reg:
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+ maxItems: 1
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+
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+ "#mbox-cells":
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+ description: |
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+ <&phandle type channel ack>
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+ phandle : Label name of controller
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+ type : Channel type
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+ channel : Channel index
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+ ack : 0: Receiver doesn't trigger an ACK interrupt to sender after receive message
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+ 1: Receiver triggers an ACK interrupt to sender after receive message
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+
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+ This mailbox support 3 type of unidirectional channels, each type
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+ has 32 channels. Following types are supported:
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+ 0 - TX channel with 32bit transmit register
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+ 1 - RX channel with 32bit receive register and IRQ support
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+ 2 - RX doorbell channel.
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+ const: 2
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+
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+required:
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+ - compatible
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+ - reg
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+ - "#mbox-cells"
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+ - interrupts
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+ - interrupt-names
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+
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+additionalProperties: false
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+
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+examples:
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+ - |
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+ reserved-memory {
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+ gen-sw-mbox@b8500000 {
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+ no-map;
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+ reg = <0 0xb8500000 0 0x1000>;
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+ };
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+ };
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+
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+ generic-software-mailbox@b8500000 {
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+ compatible = "fsl,generic-software-mbox";
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+ reg = <0 0xb8500000 0 0x1000>;
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+ #mbox-cells = <3>;
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+ interrupts = <GIC_SPI 76 IRQ_TYPE_LEVEL_HIGH>,
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+ <GIC_SPI 77 IRQ_TYPE_LEVEL_HIGH>;
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+ interrupt-names = "irq", "remote_irq";
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+ };
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diff --git a/Documentation/devicetree/bindings/net/fsl,fec.yaml b/Documentation/devicetree/bindings/net/fsl,fec.yaml
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index 18f04d110d6e..f53b6ba17d5d 100644
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--- a/Documentation/devicetree/bindings/net/fsl,fec.yaml
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+++ b/Documentation/devicetree/bindings/net/fsl,fec.yaml
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@@ -176,6 +176,30 @@ properties:
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description:
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Register bits of stop mode control, the format is <&gpr req_gpr req_bit>.
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+ fsl,rx-phy-delay-100-ns:
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+ $ref: /schemas/types.yaml#/definitions/uint32
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+ description:
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+ If present, should specify the delay (MAC-PHY) compensation
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+ in ns to be applied on packets timestamps on receive for 100 Mbps link speed
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+
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+ fsl,tx-phy-delay-100-ns:
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+ $ref: /schemas/types.yaml#/definitions/uint32
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+ description:
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+ If present, should specify the delay (MAC-PHY) compensation
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+ in ns to be applied on packets timestamps on transmit for 100 Mbps link speed
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+
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+ fsl,rx-phy-delay-1000-ns:
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+ $ref: /schemas/types.yaml#/definitions/uint32
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+ description:
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|
+ If present, should specify the delay (MAC-PHY) compensation
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+ in ns to be applied on packets timestamps on receive for 1 Gbps link speed
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+
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+ fsl,tx-phy-delay-1000-ns:
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+ $ref: /schemas/types.yaml#/definitions/uint32
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+ description:
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+ If present, should specify the delay (MAC-PHY) compensation
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+ in ns to be applied on packets timestamps on transmit for 1 Gbps link speed
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+
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mii-exclusive:
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$ref: /schemas/types.yaml#/definitions/flag
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description:
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diff --git a/Documentation/devicetree/bindings/tty/rpmsg_tty.yaml b/Documentation/devicetree/bindings/tty/rpmsg_tty.yaml
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new file mode 100644
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index 000000000000..9e11fadd16eb
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--- /dev/null
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+++ b/Documentation/devicetree/bindings/tty/rpmsg_tty.yaml
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@@ -0,0 +1,67 @@
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+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
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+%YAML 1.2
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+---
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+$id: http://devicetree.org/schemas/tty/rpmsg_tty.yaml#
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+$schema: http://devicetree.org/meta-schemas/core.yaml#
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+
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+title: rpmsg tty driver
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+
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+maintainers:
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+ - Biwen Li <biwen.li@nxp.com>
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+
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+properties:
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+ compatible:
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+ const: fsl,uart-rpbus
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+
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+ bus_id:
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+ items:
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+ - description: Used for imx srtm uart application protocol. Specify which real uart(LPUARTx/UARTx, x is instance number) will be used by a virtual tty(/dev/ttyRPMSGx), bus_id = 0xff when bus_id is not specified in dts and specified the flag(IMX_SRTM_UART_SUPPORT_MULTI_UART_MSG_FLAG).
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+ maxItems: 1
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+
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+ flags:
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+ items:
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+ - description: used for imx srtm uart application protocol(IMX_SRTM_UART_SUPPORT_MULTI_UART_MSG_FLAG: support multi uart message protocol; IMX_SRTM_UART_SPECIFY_PORT_NUM_MASK: whether specify destination uart id; IMX_SRTM_UART_PORT_NUM_MASK: which destination uart id will be used)
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+ maxItems: 1
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+
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+ status:
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+ maxItems: 1
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+
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+examples:
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+ - |
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+ #include <dt-bindings/rpmsg/imx_srtm.h>
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+
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+ uart-rpbus-0 {
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+ compatible = "fsl,uart-rpbus";
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+ bus_id = <3>; /* use uart3 */
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+ flags=<IMX_SRTM_UART_SUPPORT_MULTI_UART_MSG_FLAG>;
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+ status = "okay";
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+ }; /* /dev/ttyRPMSG0 on linux(running on acore) <--SRTM PROTOCOL--> srtm uart channel 0(endpoint on mcore) <---MULTI UART MSG PROTOCOL---> UART3(mcore is the owner) */
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+
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+ uart-rpbus-1 {
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+ compatible = "fsl,uart-rpbus";
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+ bus_id = <3>; /* use uart3 */
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+ flags=<IMX_SRTM_UART_SUPPORT_MULTI_UART_MSG_FLAG>;
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|
+ status = "okay";
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+ }; /* /dev/ttyRPMSG1 on linux(running on acore) <--SRTM PROTOCOL--> srtm uart channel 1(endpoint on mcore) <---MULTI UART MSG PROTOCOL---> UART3(mcore is the owner) */
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+
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+ uart-rpbus-2 {
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+ compatible = "fsl,uart-rpbus";
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|
+ bus_id = <2>; /* use uart2 */
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+ flags=<IMX_SRTM_UART_SUPPORT_MULTI_UART_MSG_FLAG>;
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+ status = "okay";
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+ }; /* /dev/ttyRPMSG2 on linux(running on acore) <--SRTM PROTOCOL--> srtm uart channel 2(endpoint on mcore) <---MULTI UART MSG PROTOCOL---> UART2(mcore is the owner) */
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+
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+ uart-rpbus-3 {
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+ compatible = "fsl,uart-rpbus";
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+ bus_id = <4>; /* use uart4 */
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|
+ flags=<IMX_SRTM_UART_SUPPORT_MULTI_UART_MSG_FLAG | IMX_SRTM_UART_SPECIFY_PORT_NUM_MASK | IMX_SRTM_UART_PORT_NUM_MASK(0x8)>;
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|
+ status = "okay";
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|
+ }; /* [/dev/ttyRPMSG3 on linux(running on acore) <--SRTM PROTOCOL--> srtm uart channel 3(endpoint on mcore) <---MULTI UART MSG PROTOCOL---> UART4(mcore is the owner), first board] <---MULTI UART MSG PROTOCOL--> [UARTx(mcore is the owner) <---MULTI UART MSG PROTOCOL---> srtm uart channel 8 <---SRTM PROTOCOL--> /dev/ttyRPMSG8 on linux(running on acore), second board ] */
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+
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|
+ uart-rpbus-4 {
|
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|
+ compatible = "fsl,uart-rpbus";
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|
+ bus_id = <5>; /* use uart5 */
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|
+ status = "okay";
|
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+ }; /* /dev/ttyRPMSG4 on linux(running on acore) <--SRTM PROTOCOL--> srtm uart channel 4(endpoint on mcore) <-----> UART5(mcore is the owner) <----> GPS device(The device have exclusive use of the UART5, other virtual tty cannot use UART5) */
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+
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+ /* Note: when nothing is specified(include compatible, bus_id, flags, status), it's a normal rpmsg tty. /dev/ttyRPMSG7(running on acore) <--RPMSG--> rpmsg endpoint(running on mcore) */
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diff --git a/Documentation/printk-ringbuffer.txt b/Documentation/printk-ringbuffer.txt
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new file mode 100644
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index 000000000000..6bde5dbd8545
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--- /dev/null
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+++ b/Documentation/printk-ringbuffer.txt
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@@ -0,0 +1,377 @@
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+struct printk_ringbuffer
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|
+------------------------
|
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|
+John Ogness <john.ogness@linutronix.de>
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|
+
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|
+Overview
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|
+~~~~~~~~
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|
+As the name suggests, this ring buffer was implemented specifically to serve
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|
+the needs of the printk() infrastructure. The ring buffer itself is not
|
||||||
|
+specific to printk and could be used for other purposes. _However_, the
|
||||||
|
+requirements and semantics of printk are rather unique. If you intend to use
|
||||||
|
+this ring buffer for anything other than printk, you need to be very clear on
|
||||||
|
+its features, behavior, and pitfalls.
|
||||||
|
+
|
||||||
|
+Features
|
||||||
|
+^^^^^^^^
|
||||||
|
+The printk ring buffer has the following features:
|
||||||
|
+
|
||||||
|
+- single global buffer
|
||||||
|
+- resides in initialized data section (available at early boot)
|
||||||
|
+- lockless readers
|
||||||
|
+- supports multiple writers
|
||||||
|
+- supports multiple non-consuming readers
|
||||||
|
+- safe from any context (including NMI)
|
||||||
|
+- groups bytes into variable length blocks (referenced by entries)
|
||||||
|
+- entries tagged with sequence numbers
|
||||||
|
+
|
||||||
|
+Behavior
|
||||||
|
+^^^^^^^^
|
||||||
|
+Since the printk ring buffer readers are lockless, there exists no
|
||||||
|
+synchronization between readers and writers. Basically writers are the tasks
|
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|
+in control and may overwrite any and all committed data at any time and from
|
||||||
|
+any context. For this reason readers can miss entries if they are overwritten
|
||||||
|
+before the reader was able to access the data. The reader API implementation
|
||||||
|
+is such that reader access to entries is atomic, so there is no risk of
|
||||||
|
+readers having to deal with partial or corrupt data. Also, entries are
|
||||||
|
+tagged with sequence numbers so readers can recognize if entries were missed.
|
||||||
|
+
|
||||||
|
+Writing to the ring buffer consists of 2 steps. First a writer must reserve
|
||||||
|
+an entry of desired size. After this step the writer has exclusive access
|
||||||
|
+to the memory region. Once the data has been written to memory, it needs to
|
||||||
|
+be committed to the ring buffer. After this step the entry has been inserted
|
||||||
|
+into the ring buffer and assigned an appropriate sequence number.
|
||||||
|
+
|
||||||
|
+Once committed, a writer must no longer access the data directly. This is
|
||||||
|
+because the data may have been overwritten and no longer exists. If a
|
||||||
|
+writer must access the data, it should either keep a private copy before
|
||||||
|
+committing the entry or use the reader API to gain access to the data.
|
||||||
|
+
|
||||||
|
+Because of how the data backend is implemented, entries that have been
|
||||||
|
+reserved but not yet committed act as barriers, preventing future writers
|
||||||
|
+from filling the ring buffer beyond the location of the reserved but not
|
||||||
|
+yet committed entry region. For this reason it is *important* that writers
|
||||||
|
+perform both reserve and commit as quickly as possible. Also, be aware that
|
||||||
|
+preemption and local interrupts are disabled and writing to the ring buffer
|
||||||
|
+is processor-reentrant locked during the reserve/commit window. Writers in
|
||||||
|
+NMI contexts can still preempt any other writers, but as long as these
|
||||||
|
+writers do not write a large amount of data with respect to the ring buffer
|
||||||
|
+size, this should not become an issue.
|
||||||
|
+
|
||||||
|
+API
|
||||||
|
+~~~
|
||||||
|
+
|
||||||
|
+Declaration
|
||||||
|
+^^^^^^^^^^^
|
||||||
|
+The printk ring buffer can be instantiated as a static structure:
|
||||||
|
+
|
||||||
|
+ /* declare a static struct printk_ringbuffer */
|
||||||
|
+ #define DECLARE_STATIC_PRINTKRB(name, szbits, cpulockptr)
|
||||||
|
+
|
||||||
|
+The value of szbits specifies the size of the ring buffer in bits. The
|
||||||
|
+cpulockptr field is a pointer to a prb_cpulock struct that is used to
|
||||||
|
+perform processor-reentrant spin locking for the writers. It is specified
|
||||||
|
+externally because it may be used for multiple ring buffers (or other
|
||||||
|
+code) to synchronize writers without risk of deadlock.
|
||||||
|
+
|
||||||
|
+Here is an example of a declaration of a printk ring buffer specifying a
|
||||||
|
+32KB (2^15) ring buffer:
|
||||||
|
+
|
||||||
|
+....
|
||||||
|
+DECLARE_STATIC_PRINTKRB_CPULOCK(rb_cpulock);
|
||||||
|
+DECLARE_STATIC_PRINTKRB(rb, 15, &rb_cpulock);
|
||||||
|
+....
|
||||||
|
+
|
||||||
|
+If writers will be using multiple ring buffers and the ordering of that usage
|
||||||
|
+is not clear, the same prb_cpulock should be used for both ring buffers.
|
||||||
|
+
|
||||||
|
+Writer API
|
||||||
|
+^^^^^^^^^^
|
||||||
|
+The writer API consists of 2 functions. The first is to reserve an entry in
|
||||||
|
+the ring buffer, the second is to commit that data to the ring buffer. The
|
||||||
|
+reserved entry information is stored within a provided `struct prb_handle`.
|
||||||
|
+
|
||||||
|
+ /* reserve an entry */
|
||||||
|
+ char *prb_reserve(struct prb_handle *h, struct printk_ringbuffer *rb,
|
||||||
|
+ unsigned int size);
|
||||||
|
+
|
||||||
|
+ /* commit a reserved entry to the ring buffer */
|
||||||
|
+ void prb_commit(struct prb_handle *h);
|
||||||
|
+
|
||||||
|
+Here is an example of a function to write data to a ring buffer:
|
||||||
|
+
|
||||||
|
+....
|
||||||
|
+int write_data(struct printk_ringbuffer *rb, char *data, int size)
|
||||||
|
+{
|
||||||
|
+ struct prb_handle h;
|
||||||
|
+ char *buf;
|
||||||
|
+
|
||||||
|
+ buf = prb_reserve(&h, rb, size);
|
||||||
|
+ if (!buf)
|
||||||
|
+ return -1;
|
||||||
|
+ memcpy(buf, data, size);
|
||||||
|
+ prb_commit(&h);
|
||||||
|
+
|
||||||
|
+ return 0;
|
||||||
|
+}
|
||||||
|
+....
|
||||||
|
+
|
||||||
|
+Pitfalls
|
||||||
|
+++++++++
|
||||||
|
+Be aware that prb_reserve() can fail. A retry might be successful, but it
|
||||||
|
+depends entirely on whether or not the next part of the ring buffer to
|
||||||
|
+overwrite belongs to reserved but not yet committed entries of other writers.
|
||||||
|
+Writers can use the prb_inc_lost() function to allow readers to notice that a
|
||||||
|
+message was lost.
|
||||||
|
+
|
||||||
|
+Reader API
|
||||||
|
+^^^^^^^^^^
|
||||||
|
+The reader API utilizes a `struct prb_iterator` to track the reader's
|
||||||
|
+position in the ring buffer.
|
||||||
|
+
|
||||||
|
+ /* declare a pre-initialized static iterator for a ring buffer */
|
||||||
|
+ #define DECLARE_STATIC_PRINTKRB_ITER(name, rbaddr)
|
||||||
|
+
|
||||||
|
+ /* initialize iterator for a ring buffer (if static macro NOT used) */
|
||||||
|
+ void prb_iter_init(struct prb_iterator *iter,
|
||||||
|
+ struct printk_ringbuffer *rb, u64 *seq);
|
||||||
|
+
|
||||||
|
+ /* make a deep copy of an iterator */
|
||||||
|
+ void prb_iter_copy(struct prb_iterator *dest,
|
||||||
|
+ struct prb_iterator *src);
|
||||||
|
+
|
||||||
|
+ /* non-blocking, advance to next entry (and read the data) */
|
||||||
|
+ int prb_iter_next(struct prb_iterator *iter, char *buf,
|
||||||
|
+ int size, u64 *seq);
|
||||||
|
+
|
||||||
|
+ /* blocking, advance to next entry (and read the data) */
|
||||||
|
+ int prb_iter_wait_next(struct prb_iterator *iter, char *buf,
|
||||||
|
+ int size, u64 *seq);
|
||||||
|
+
|
||||||
|
+ /* position iterator at the entry seq */
|
||||||
|
+ int prb_iter_seek(struct prb_iterator *iter, u64 seq);
|
||||||
|
+
|
||||||
|
+ /* read data at current position */
|
||||||
|
+ int prb_iter_data(struct prb_iterator *iter, char *buf,
|
||||||
|
+ int size, u64 *seq);
|
||||||
|
+
|
||||||
|
+Typically prb_iter_data() is not needed because the data can be retrieved
|
||||||
|
+directly with prb_iter_next().
|
||||||
|
+
|
||||||
|
+Here is an example of a non-blocking function that will read all the data in
|
||||||
|
+a ring buffer:
|
||||||
|
+
|
||||||
|
+....
|
||||||
|
+void read_all_data(struct printk_ringbuffer *rb, char *buf, int size)
|
||||||
|
+{
|
||||||
|
+ struct prb_iterator iter;
|
||||||
|
+ u64 prev_seq = 0;
|
||||||
|
+ u64 seq;
|
||||||
|
+ int ret;
|
||||||
|
+
|
||||||
|
+ prb_iter_init(&iter, rb, NULL);
|
||||||
|
+
|
||||||
|
+ for (;;) {
|
||||||
|
+ ret = prb_iter_next(&iter, buf, size, &seq);
|
||||||
|
+ if (ret > 0) {
|
||||||
|
+ if (seq != ++prev_seq) {
|
||||||
|
+ /* "seq - prev_seq" entries missed */
|
||||||
|
+ prev_seq = seq;
|
||||||
|
+ }
|
||||||
|
+ /* process buf here */
|
||||||
|
+ } else if (ret == 0) {
|
||||||
|
+ /* hit the end, done */
|
||||||
|
+ break;
|
||||||
|
+ } else if (ret < 0) {
|
||||||
|
+ /*
|
||||||
|
+ * iterator is invalid, a writer overtook us, reset the
|
||||||
|
+ * iterator and keep going, entries were missed
|
||||||
|
+ */
|
||||||
|
+ prb_iter_init(&iter, rb, NULL);
|
||||||
|
+ }
|
||||||
|
+ }
|
||||||
|
+}
|
||||||
|
+....
|
||||||
|
+
|
||||||
|
+Pitfalls
|
||||||
|
+++++++++
|
||||||
|
+The reader's iterator can become invalid at any time because the reader was
|
||||||
|
+overtaken by a writer. Typically the reader should reset the iterator back
|
||||||
|
+to the current oldest entry (which will be newer than the entry the reader
|
||||||
|
+was at) and continue, noting the number of entries that were missed.
|
||||||
|
+
|
||||||
|
+Utility API
|
||||||
|
+^^^^^^^^^^^
|
||||||
|
+Several functions are available as convenience for external code.
|
||||||
|
+
|
||||||
|
+ /* query the size of the data buffer */
|
||||||
|
+ int prb_buffer_size(struct printk_ringbuffer *rb);
|
||||||
|
+
|
||||||
|
+ /* skip a seq number to signify a lost record */
|
||||||
|
+ void prb_inc_lost(struct printk_ringbuffer *rb);
|
||||||
|
+
|
||||||
|
+ /* processor-reentrant spin lock */
|
||||||
|
+ void prb_lock(struct prb_cpulock *cpu_lock, unsigned int *cpu_store);
|
||||||
|
+
|
||||||
|
+ /* processor-reentrant spin unlock */
|
||||||
|
+ void prb_lock(struct prb_cpulock *cpu_lock, unsigned int *cpu_store);
|
||||||
|
+
|
||||||
|
+Pitfalls
|
||||||
|
+++++++++
|
||||||
|
+Although the value returned by prb_buffer_size() does represent an absolute
|
||||||
|
+upper bound, the amount of data that can be stored within the ring buffer
|
||||||
|
+is actually less because of the additional storage space of a header for each
|
||||||
|
+entry.
|
||||||
|
+
|
||||||
|
+The prb_lock() and prb_unlock() functions can be used to synchronize between
|
||||||
|
+ring buffer writers and other external activities. The function of a
|
||||||
|
+processor-reentrant spin lock is to disable preemption and local interrupts
|
||||||
|
+and synchronize against other processors. It does *not* protect against
|
||||||
|
+multiple contexts of a single processor, i.e NMI.
|
||||||
|
+
|
||||||
|
+Implementation
|
||||||
|
+~~~~~~~~~~~~~~
|
||||||
|
+This section describes several of the implementation concepts and details to
|
||||||
|
+help developers better understand the code.
|
||||||
|
+
|
||||||
|
+Entries
|
||||||
|
+^^^^^^^
|
||||||
|
+All ring buffer data is stored within a single static byte array. The reason
|
||||||
|
+for this is to ensure that any pointers to the data (past and present) will
|
||||||
|
+always point to valid memory. This is important because the lockless readers
|
||||||
|
+may be preempted for long periods of time and when they resume may be working
|
||||||
|
+with expired pointers.
|
||||||
|
+
|
||||||
|
+Entries are identified by start index and size. (The start index plus size
|
||||||
|
+is the start index of the next entry.) The start index is not simply an
|
||||||
|
+offset into the byte array, but rather a logical position (lpos) that maps
|
||||||
|
+directly to byte array offsets.
|
||||||
|
+
|
||||||
|
+For example, for a byte array of 1000, an entry may have have a start index
|
||||||
|
+of 100. Another entry may have a start index of 1100. And yet another 2100.
|
||||||
|
+All of these entry are pointing to the same memory region, but only the most
|
||||||
|
+recent entry is valid. The other entries are pointing to valid memory, but
|
||||||
|
+represent entries that have been overwritten.
|
||||||
|
+
|
||||||
|
+Note that due to overflowing, the most recent entry is not necessarily the one
|
||||||
|
+with the highest lpos value. Indeed, the printk ring buffer initializes its
|
||||||
|
+data such that an overflow happens relatively quickly in order to validate the
|
||||||
|
+handling of this situation. The implementation assumes that an lpos (unsigned
|
||||||
|
+long) will never completely wrap while a reader is preempted. If this were to
|
||||||
|
+become an issue, the seq number (which never wraps) could be used to increase
|
||||||
|
+the robustness of handling this situation.
|
||||||
|
+
|
||||||
|
+Buffer Wrapping
|
||||||
|
+^^^^^^^^^^^^^^^
|
||||||
|
+If an entry starts near the end of the byte array but would extend beyond it,
|
||||||
|
+a special terminating entry (size = -1) is inserted into the byte array and
|
||||||
|
+the real entry is placed at the beginning of the byte array. This can waste
|
||||||
|
+space at the end of the byte array, but simplifies the implementation by
|
||||||
|
+allowing writers to always work with contiguous buffers.
|
||||||
|
+
|
||||||
|
+Note that the size field is the first 4 bytes of the entry header. Also note
|
||||||
|
+that calc_next() always ensures that there are at least 4 bytes left at the
|
||||||
|
+end of the byte array to allow room for a terminating entry.
|
||||||
|
+
|
||||||
|
+Ring Buffer Pointers
|
||||||
|
+^^^^^^^^^^^^^^^^^^^^
|
||||||
|
+Three pointers (lpos values) are used to manage the ring buffer:
|
||||||
|
+
|
||||||
|
+ - _tail_: points to the oldest entry
|
||||||
|
+ - _head_: points to where the next new committed entry will be
|
||||||
|
+ - _reserve_: points to where the next new reserved entry will be
|
||||||
|
+
|
||||||
|
+These pointers always maintain a logical ordering:
|
||||||
|
+
|
||||||
|
+ tail <= head <= reserve
|
||||||
|
+
|
||||||
|
+The reserve pointer moves forward when a writer reserves a new entry. The
|
||||||
|
+head pointer moves forward when a writer commits a new entry.
|
||||||
|
+
|
||||||
|
+The reserve pointer cannot overwrite the tail pointer in a wrap situation. In
|
||||||
|
+such a situation, the tail pointer must be "pushed forward", thus
|
||||||
|
+invalidating that oldest entry. Readers identify if they are accessing a
|
||||||
|
+valid entry by ensuring their entry pointer is `>= tail && < head`.
|
||||||
|
+
|
||||||
|
+If the tail pointer is equal to the head pointer, it cannot be pushed and any
|
||||||
|
+reserve operation will fail. The only resolution is for writers to commit
|
||||||
|
+their reserved entries.
|
||||||
|
+
|
||||||
|
+Processor-Reentrant Locking
|
||||||
|
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||||
|
+The purpose of the processor-reentrant locking is to limit the interruption
|
||||||
|
+scenarios of writers to 2 contexts. This allows for a simplified
|
||||||
|
+implementation where:
|
||||||
|
+
|
||||||
|
+- The reserve/commit window only exists on 1 processor at a time. A reserve
|
||||||
|
+ can never fail due to uncommitted entries of other processors.
|
||||||
|
+
|
||||||
|
+- When committing entries, it is trivial to handle the situation when
|
||||||
|
+ subsequent entries have already been committed, i.e. managing the head
|
||||||
|
+ pointer.
|
||||||
|
+
|
||||||
|
+Performance
|
||||||
|
+~~~~~~~~~~~
|
||||||
|
+Some basic tests were performed on a quad Intel(R) Xeon(R) CPU E5-2697 v4 at
|
||||||
|
+2.30GHz (36 cores / 72 threads). All tests involved writing a total of
|
||||||
|
+32,000,000 records at an average of 33 bytes each. Each writer was pinned to
|
||||||
|
+its own CPU and would write as fast as it could until a total of 32,000,000
|
||||||
|
+records were written. All tests involved 2 readers that were both pinned
|
||||||
|
+together to another CPU. Each reader would read as fast as it could and track
|
||||||
|
+how many of the 32,000,000 records it could read. All tests used a ring buffer
|
||||||
|
+of 16KB in size, which holds around 350 records (header + data for each
|
||||||
|
+entry).
|
||||||
|
+
|
||||||
|
+The only difference between the tests is the number of writers (and thus also
|
||||||
|
+the number of records per writer). As more writers are added, the time to
|
||||||
|
+write a record increases. This is because data pointers, modified via cmpxchg,
|
||||||
|
+and global data access in general become more contended.
|
||||||
|
+
|
||||||
|
+1 writer
|
||||||
|
+^^^^^^^^
|
||||||
|
+ runtime: 0m 18s
|
||||||
|
+ reader1: 16219900/32000000 (50%) records
|
||||||
|
+ reader2: 16141582/32000000 (50%) records
|
||||||
|
+
|
||||||
|
+2 writers
|
||||||
|
+^^^^^^^^^
|
||||||
|
+ runtime: 0m 32s
|
||||||
|
+ reader1: 16327957/32000000 (51%) records
|
||||||
|
+ reader2: 16313988/32000000 (50%) records
|
||||||
|
+
|
||||||
|
+4 writers
|
||||||
|
+^^^^^^^^^
|
||||||
|
+ runtime: 0m 42s
|
||||||
|
+ reader1: 16421642/32000000 (51%) records
|
||||||
|
+ reader2: 16417224/32000000 (51%) records
|
||||||
|
+
|
||||||
|
+8 writers
|
||||||
|
+^^^^^^^^^
|
||||||
|
+ runtime: 0m 43s
|
||||||
|
+ reader1: 16418300/32000000 (51%) records
|
||||||
|
+ reader2: 16432222/32000000 (51%) records
|
||||||
|
+
|
||||||
|
+16 writers
|
||||||
|
+^^^^^^^^^^
|
||||||
|
+ runtime: 0m 54s
|
||||||
|
+ reader1: 16539189/32000000 (51%) records
|
||||||
|
+ reader2: 16542711/32000000 (51%) records
|
||||||
|
+
|
||||||
|
+32 writers
|
||||||
|
+^^^^^^^^^^
|
||||||
|
+ runtime: 1m 13s
|
||||||
|
+ reader1: 16731808/32000000 (52%) records
|
||||||
|
+ reader2: 16735119/32000000 (52%) records
|
||||||
|
+
|
||||||
|
+Comments
|
||||||
|
+^^^^^^^^
|
||||||
|
+It is particularly interesting to compare/contrast the 1-writer and 32-writer
|
||||||
|
+tests. Despite the writing of the 32,000,000 records taking over 4 times
|
||||||
|
+longer, the readers (which perform no cmpxchg) were still unable to keep up.
|
||||||
|
+This shows that the memory contention between the increasing number of CPUs
|
||||||
|
+also has a dramatic effect on readers.
|
||||||
|
+
|
||||||
|
+It should also be noted that in all cases each reader was able to read >=50%
|
||||||
|
+of the records. This means that a single reader would have been able to keep
|
||||||
|
+up with the writer(s) in all cases, becoming slightly easier as more writers
|
||||||
|
+are added. This was the purpose of pinning 2 readers to 1 CPU: to observe how
|
||||||
|
+maximum reader performance changes.
|
||||||
|
--
|
||||||
|
2.34.1
|
||||||
|
|
||||||
File diff suppressed because it is too large
Load Diff
File diff suppressed because it is too large
Load Diff
File diff suppressed because it is too large
Load Diff
File diff suppressed because it is too large
Load Diff
|
|
@ -0,0 +1,28 @@
|
||||||
|
From 98287df3a9d231a31fbc8b2e15be6174d6af1673 Mon Sep 17 00:00:00 2001
|
||||||
|
From: Mike Engel <Mike.Engel@digi.com>
|
||||||
|
Date: Mon, 26 Feb 2024 09:43:05 +0100
|
||||||
|
Subject: [PATCH 09/10] init: add NXP RT support
|
||||||
|
|
||||||
|
Signed-off-by: Mike Engel <Mike.Engel@digi.com>
|
||||||
|
---
|
||||||
|
init/Kconfig | 4 ++++
|
||||||
|
1 file changed, 4 insertions(+)
|
||||||
|
|
||||||
|
diff --git a/init/Kconfig b/init/Kconfig
|
||||||
|
index de255842f5d0..d45312780b3a 100644
|
||||||
|
--- a/init/Kconfig
|
||||||
|
+++ b/init/Kconfig
|
||||||
|
@@ -1582,6 +1582,10 @@ config PRINTK
|
||||||
|
very difficult to diagnose system problems, saying N here is
|
||||||
|
strongly discouraged.
|
||||||
|
|
||||||
|
+config HAVE_ATOMIC_CONSOLE
|
||||||
|
+ bool
|
||||||
|
+ default n
|
||||||
|
+
|
||||||
|
config BUG
|
||||||
|
bool "BUG() support" if EXPERT
|
||||||
|
default y
|
||||||
|
--
|
||||||
|
2.34.1
|
||||||
|
|
||||||
|
|
@ -0,0 +1,31 @@
|
||||||
|
..........................................................................
|
||||||
|
. WARNING
|
||||||
|
.
|
||||||
|
. This file is a kernel configuration fragment, and not a full kernel
|
||||||
|
. configuration file. The final kernel configuration is made up of
|
||||||
|
. an assembly of processed fragments, each of which is designed to
|
||||||
|
. capture a specific part of the final configuration (e.g. platform
|
||||||
|
. configuration, feature configuration, and board specific hardware
|
||||||
|
. configuration). For more information on kernel configuration, please
|
||||||
|
. consult the product documentation.
|
||||||
|
.
|
||||||
|
..........................................................................
|
||||||
|
CONFIG_PREEMPT_RT=y
|
||||||
|
CONFIG_EXPERT=y
|
||||||
|
|
||||||
|
# disable SCHED_MC
|
||||||
|
# CONFIG_MCPM is not set
|
||||||
|
|
||||||
|
# Disable CPUFREQ and CPUIDLE
|
||||||
|
# CONFIG_CPU_FREQ is not set
|
||||||
|
# CONFIG_CPU_IDLE is not set
|
||||||
|
|
||||||
|
# CONFIG_NUMA_BALANCING in not set
|
||||||
|
# CONFIG_TRANSPARENT_HUGEPAGE is not set
|
||||||
|
# CONFIG_EFI_DISABLE_RUNTIME is not set
|
||||||
|
CONFIG_MEDIA_SUPPORT_FILTER=y
|
||||||
|
CONFIG_FRAMEBUFFER_CONSOLE=y
|
||||||
|
# CONFIG_LEDS_TRIGGER_CPU is not set
|
||||||
|
# CONFIG_DEBUG_KERNEL is not set
|
||||||
|
# CONFIG_HID_MULTITOUCH is not set
|
||||||
|
CONFIG_FRAMEBUFFER_CONSOLE=y
|
||||||
|
|
@ -1,8 +1,27 @@
|
||||||
# Copyright (C) 2023 Digi International
|
# Copyright (C) 2023-2024 Digi International
|
||||||
|
|
||||||
require recipes-kernel/linux/linux-dey.inc
|
require recipes-kernel/linux/linux-dey.inc
|
||||||
|
|
||||||
SRCBRANCH = "v6.1.55/nxp/master"
|
SRCBRANCH = "v6.1.55/nxp/master"
|
||||||
|
|
||||||
|
# Patch series for RT Kernel
|
||||||
|
NXP_RT_PATCHES = " \
|
||||||
|
file://0001-arch-arm-add-NXP-RT-support.patch \
|
||||||
|
file://0002-RT-add-RT-localversion.patch \
|
||||||
|
file://0003-arch-arm64-add-NXP-RT-support.patch \
|
||||||
|
file://0004-Documentation-add-NXP-RT-support.patch \
|
||||||
|
file://0005-include-add-NXP-RT-support.patch \
|
||||||
|
file://0006-kernel-add-NXP-RT-support.patch \
|
||||||
|
file://0007-drivers-add-NXP-RT-support.patch \
|
||||||
|
file://0008-net-add-RT-NXP-support.patch \
|
||||||
|
file://0009-init-add-NXP-RT-support.patch \
|
||||||
|
file://nxp_rt_conf.cfg \
|
||||||
|
"
|
||||||
|
|
||||||
|
SRC_URI:append = " \
|
||||||
|
${@bb.utils.contains('DISTRO_FEATURES', 'rt', '${NXP_RT_PATCHES}', '', d)} \
|
||||||
|
"
|
||||||
|
|
||||||
SRCREV = "${AUTOREV}"
|
SRCREV = "${AUTOREV}"
|
||||||
|
|
||||||
# Blacklist btnxpuart module. It will be managed by the bluetooth-init script
|
# Blacklist btnxpuart module. It will be managed by the bluetooth-init script
|
||||||
|
|
|
||||||
Loading…
Reference in New Issue