[PATCH iv4 0/2] Add L1 and L2 error detection for A53 and A57

[PATCH iv4 0/2] Add L1 and L2 error detection for A53 and A57

[Sascha Hauer]

Hi All,

As mentioned by Marc and Mark usage of the implementation defined
registers is not generally safe, they can't be used in virtualized
environments or when EL3 already uses the same registers. This is
probably the last attempt to get this upstream, I added an additional
property to the CPU device nodes to be set explicitly when using these
registers is safe and desired.

Sascha

Changes since v3:
- Add edac-enabled property to make EDAC support optional

Changes since v2:
- drop usage of virtual dt node (Robh)
- use read_sysreg_s instead of open coded variant (James Morse)
- separate error retrieving from error reporting
- use smp_call_function_single rather than smp_call_function_single_async
- make driver single instance and register all 'cpu' hierarchy up front once

Changes since v1:
- Split dt-binding into separate patch
- Sort local function variables in reverse-xmas tree order
- drop unnecessary comparison and make variable bool

Sascha Hauer (2):
  drivers/edac: Add L1 and L2 error detection for A53 and A57
  dt-bindings: arm: cpus: Add edac-enabled property

 .../devicetree/bindings/arm/cpus.yaml         |   6 +
 drivers/edac/Kconfig                          |   6 +
 drivers/edac/Makefile                         |   1 +
 drivers/edac/cortex_arm64_l1_l2.c             | 221 ++++++++++++++++++
 4 files changed, 234 insertions(+)
 create mode 100644 drivers/edac/cortex_arm64_l1_l2.c

-- 
2.20.1

[PATCH 1/2] drivers/edac: Add L1 and L2 error detection for A53 and A57

[Sascha Hauer]

The Cortex A53 and A57 cores have error detection capabilities for the
L1/L2 Caches, this patch adds a driver for them.

Unfortunately there is no robust way to inject errors into the caches,
so this driver doesn't contain any code to actually test it. It has
been tested though with code taken from an older version of this driver
found here: https://lkml.org/lkml/2018/3/14/1203. For reasons stated
in this thread the error injection code is not suitable for mainline,
so it is removed from the driver.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 drivers/edac/Kconfig              |   6 +
 drivers/edac/Makefile             |   1 +
 drivers/edac/cortex_arm64_l1_l2.c | 218 ++++++++++++++++++++++++++++++
 3 files changed, 225 insertions(+)
 create mode 100644 drivers/edac/cortex_arm64_l1_l2.c

diff --git a/drivers/edac/Kconfig b/drivers/edac/Kconfig
index 81c42664f21b..116ad56534a4 100644
--- a/drivers/edac/Kconfig
+++ b/drivers/edac/Kconfig
@@ -539,4 +539,10 @@ config EDAC_DMC520
 	  Support for error detection and correction on the
 	  SoCs with ARM DMC-520 DRAM controller.
 
+config EDAC_CORTEX_ARM64_L1_L2
+	tristate "ARM Cortex A57/A53"
+	depends on ARM64
+	help
+	  Support for L1/L2 cache error detection on ARM Cortex A57 and A53.
+
 endif # EDAC
diff --git a/drivers/edac/Makefile b/drivers/edac/Makefile
index 464d3d8d850a..a324fbc1693e 100644
--- a/drivers/edac/Makefile
+++ b/drivers/edac/Makefile
@@ -89,3 +89,4 @@ obj-$(CONFIG_EDAC_QCOM)			+= qcom_edac.o
 obj-$(CONFIG_EDAC_ASPEED)		+= aspeed_edac.o
 obj-$(CONFIG_EDAC_BLUEFIELD)		+= bluefield_edac.o
 obj-$(CONFIG_EDAC_DMC520)		+= dmc520_edac.o
+obj-$(CONFIG_EDAC_CORTEX_ARM64_L1_L2)	+= cortex_arm64_l1_l2.o
diff --git a/drivers/edac/cortex_arm64_l1_l2.c b/drivers/edac/cortex_arm64_l1_l2.c
new file mode 100644
index 000000000000..3b1e2f3ccab6
--- /dev/null
+++ b/drivers/edac/cortex_arm64_l1_l2.c
@@ -0,0 +1,218 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Cortex A57 and A53 EDAC L1 and L2 cache error detection
+ *
+ * Copyright (c) 2020 Pengutronix, Sascha Hauer <s.hauer@pengutronix.de>
+ *
+ * Based on Code from:
+ * Copyright (c) 2018, NXP Semiconductor
+ * Author: York Sun <york.sun@nxp.com>
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/of_platform.h>
+#include <linux/of_device.h>
+#include <linux/bitfield.h>
+#include <asm/smp_plat.h>
+
+#include "edac_module.h"
+
+#define DRVNAME				"cortex-arm64-edac"
+
+#define CPUMERRSR_EL1_RAMID		GENMASK(30, 24)
+
+#define CPUMERRSR_EL1_VALID		BIT(31)
+#define CPUMERRSR_EL1_FATAL		BIT(63)
+
+#define L1_I_TAG_RAM			0x00
+#define L1_I_DATA_RAM			0x01
+#define L1_D_TAG_RAM			0x08
+#define L1_D_DATA_RAM			0x09
+#define L1_D_DIRTY_RAM			0x14
+#define TLB_RAM				0x18
+
+#define L2MERRSR_EL1_VALID		BIT(31)
+#define L2MERRSR_EL1_FATAL		BIT(63)
+
+struct merrsr {
+	u64 cpumerr;
+	u64 l2merr;
+};
+
+#define MESSAGE_SIZE 64
+
+#define SYS_CPUMERRSR_EL1			sys_reg(3, 1, 15, 2, 2)
+#define SYS_L2MERRSR_EL1			sys_reg(3, 1, 15, 2, 3)
+
+static struct cpumask compat_mask;
+
+static void report_errors(struct edac_device_ctl_info *edac_ctl, int cpu,
+			  struct merrsr *merrsr)
+{
+	char msg[MESSAGE_SIZE];
+	u64 cpumerr = merrsr->cpumerr;
+	u64 l2merr = merrsr->l2merr;
+
+	if (cpumerr & CPUMERRSR_EL1_VALID) {
+		const char *str;
+		bool fatal = cpumerr & CPUMERRSR_EL1_FATAL;
+
+		switch (FIELD_GET(CPUMERRSR_EL1_RAMID, cpumerr)) {
+		case L1_I_TAG_RAM:
+			str = "L1-I Tag RAM";
+			break;
+		case L1_I_DATA_RAM:
+			str = "L1-I Data RAM";
+			break;
+		case L1_D_TAG_RAM:
+			str = "L1-D Tag RAM";
+			break;
+		case L1_D_DATA_RAM:
+			str = "L1-D Data RAM";
+			break;
+		case L1_D_DIRTY_RAM:
+			str = "L1 Dirty RAM";
+			break;
+		case TLB_RAM:
+			str = "TLB RAM";
+			break;
+		default:
+			str = "unknown";
+			break;
+		}
+
+		snprintf(msg, MESSAGE_SIZE, "%s %s error(s) on CPU %d",
+			 str, fatal ? "fatal" : "correctable", cpu);
+
+		if (fatal)
+			edac_device_handle_ue(edac_ctl, cpu, 0, msg);
+		else
+			edac_device_handle_ce(edac_ctl, cpu, 0, msg);
+	}
+
+	if (l2merr & L2MERRSR_EL1_VALID) {
+		bool fatal = l2merr & L2MERRSR_EL1_FATAL;
+
+		snprintf(msg, MESSAGE_SIZE, "L2 %s error(s) on CPU %d",
+			 fatal ? "fatal" : "correctable", cpu);
+		if (fatal)
+			edac_device_handle_ue(edac_ctl, cpu, 1, msg);
+		else
+			edac_device_handle_ce(edac_ctl, cpu, 1, msg);
+	}
+}
+
+static void read_errors(void *data)
+{
+	struct merrsr *merrsr = data;
+
+	merrsr->cpumerr = read_sysreg_s(SYS_CPUMERRSR_EL1);
+	write_sysreg_s(0, SYS_CPUMERRSR_EL1);
+	merrsr->l2merr = read_sysreg_s(SYS_L2MERRSR_EL1);
+	write_sysreg_s(0, SYS_L2MERRSR_EL1);
+}
+
+static void cortex_arm64_edac_check(struct edac_device_ctl_info *edac_ctl)
+{
+	struct merrsr merrsr;
+	int cpu;
+
+	for_each_cpu_and(cpu, cpu_online_mask, &compat_mask) {
+		smp_call_function_single(cpu, read_errors, &merrsr, true);
+		report_errors(edac_ctl, cpu, &merrsr);
+	}
+}
+
+static int cortex_arm64_edac_probe(struct platform_device *pdev)
+{
+	struct edac_device_ctl_info *edac_ctl;
+	struct device *dev = &pdev->dev;
+	int rc;
+
+	edac_ctl = edac_device_alloc_ctl_info(0, "cpu",
+					      num_possible_cpus(), "L", 2, 1, NULL, 0,
+					      edac_device_alloc_index());
+	if (!edac_ctl)
+		return -ENOMEM;
+
+	edac_ctl->edac_check = cortex_arm64_edac_check;
+	edac_ctl->dev = dev;
+	edac_ctl->mod_name = dev_name(dev);
+	edac_ctl->dev_name = dev_name(dev);
+	edac_ctl->ctl_name = DRVNAME;
+	dev_set_drvdata(dev, edac_ctl);
+
+	rc = edac_device_add_device(edac_ctl);
+	if (rc)
+		goto out_dev;
+
+	return 0;
+
+out_dev:
+	edac_device_free_ctl_info(edac_ctl);
+
+	return rc;
+}
+
+static int cortex_arm64_edac_remove(struct platform_device *pdev)
+{
+	struct edac_device_ctl_info *edac_ctl = dev_get_drvdata(&pdev->dev);
+
+	edac_device_del_device(edac_ctl->dev);
+	edac_device_free_ctl_info(edac_ctl);
+
+	return 0;
+}
+
+static const struct of_device_id cortex_arm64_edac_of_match[] = {
+	{ .compatible = "arm,cortex-a53" },
+	{ .compatible = "arm,cortex-a57" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, cortex_arm64_edac_of_match);
+
+static struct platform_driver cortex_arm64_edac_driver = {
+	.probe = cortex_arm64_edac_probe,
+	.remove = cortex_arm64_edac_remove,
+	.driver = {
+		.name = DRVNAME,
+	},
+};
+
+static int __init cortex_arm64_edac_driver_init(void)
+{
+	struct device_node *np;
+	int cpu;
+	struct platform_device *pdev;
+	int err;
+
+	for_each_possible_cpu(cpu) {
+		np = of_get_cpu_node(cpu, NULL);
+
+		if (of_match_node(cortex_arm64_edac_of_match, np))
+			cpumask_set_cpu(cpu, &compat_mask);
+	}
+
+	if (cpumask_empty(&compat_mask))
+		return 0;
+
+	err = platform_driver_register(&cortex_arm64_edac_driver);
+        if (err)
+                return err;
+
+	pdev = platform_device_register_simple(DRVNAME, -1, NULL, 0);
+	if (IS_ERR(pdev)) {
+		pr_err("failed to register cortex arm64 edac device\n");
+		platform_driver_unregister(&cortex_arm64_edac_driver);
+		return PTR_ERR(pdev);
+	}
+
+	return 0;
+}
+
+device_initcall(cortex_arm64_edac_driver_init);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");
+MODULE_DESCRIPTION("Cortex A57 and A53 L1 and L2 cache EDAC driver");
-- 
2.20.1

[PATCH 2/2] dt-bindings: arm: cpus: Add edac-enabled property

[Sascha Hauer]

Some CPUs like the Cortex-A53 and Cortex-A57 have Error Detection And
Correction (EDAC) support on their L1 and L2 caches. This is implemented
in implementation defined registers, so usage of this functionality is
not safe in virtualized environments or when EL3 already uses these
registers.
This patch adds a edac-enabled flag which can be explicitly set when
EDAC can be used.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 Documentation/devicetree/bindings/arm/cpus.yaml | 6 ++++++
 drivers/edac/cortex_arm64_l1_l2.c               | 7 +++++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/arm/cpus.yaml b/Documentation/devicetree/bindings/arm/cpus.yaml
index f02fd10de604..80dcf90f3e78 100644
--- a/Documentation/devicetree/bindings/arm/cpus.yaml
+++ b/Documentation/devicetree/bindings/arm/cpus.yaml
@@ -269,6 +269,12 @@ properties:
       For PSCI based platforms, the name corresponding to the index of the PSCI
       PM domain provider, must be "psci".
 
+  edac-enabled:
+    $ref: '/schemas/types.yaml#/definitions/flag'
+    description:
+      Some CPUs support Error Detection And Correction (EDAC) on their L1 and
+      L2 caches. This flag marks this function as usable.
+
   qcom,saw:
     $ref: '/schemas/types.yaml#/definitions/phandle'
     description: |
diff --git a/drivers/edac/cortex_arm64_l1_l2.c b/drivers/edac/cortex_arm64_l1_l2.c
index 3b1e2f3ccab6..6d5355bae80c 100644
--- a/drivers/edac/cortex_arm64_l1_l2.c
+++ b/drivers/edac/cortex_arm64_l1_l2.c
@@ -190,8 +190,11 @@ static int __init cortex_arm64_edac_driver_init(void)
 	for_each_possible_cpu(cpu) {
 		np = of_get_cpu_node(cpu, NULL);
 
-		if (of_match_node(cortex_arm64_edac_of_match, np))
-			cpumask_set_cpu(cpu, &compat_mask);
+		if (!of_match_node(cortex_arm64_edac_of_match, np))
+			continue;
+		if (!of_property_read_bool(np, "edac-enabled"))
+			continue;
+		cpumask_set_cpu(cpu, &compat_mask);
 	}
 
 	if (cpumask_empty(&compat_mask))
-- 
2.20.1

Re: [PATCH 2/2] dt-bindings: arm: cpus: Add edac-enabled property

[Sascha Hauer]

On Mon, Feb 01, 2021 at 12:57:53PM +0100, Sascha Hauer wrote:
> Some CPUs like the Cortex-A53 and Cortex-A57 have Error Detection And
> Correction (EDAC) support on their L1 and L2 caches. This is implemented
> in implementation defined registers, so usage of this functionality is
> not safe in virtualized environments or when EL3 already uses these
> registers.
> This patch adds a edac-enabled flag which can be explicitly set when
> EDAC can be used.
> 
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
>  Documentation/devicetree/bindings/arm/cpus.yaml | 6 ++++++
>  drivers/edac/cortex_arm64_l1_l2.c               | 7 +++++--
>  2 files changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/arm/cpus.yaml b/Documentation/devicetree/bindings/arm/cpus.yaml
> index f02fd10de604..80dcf90f3e78 100644
> --- a/Documentation/devicetree/bindings/arm/cpus.yaml
> +++ b/Documentation/devicetree/bindings/arm/cpus.yaml
> @@ -269,6 +269,12 @@ properties:
>        For PSCI based platforms, the name corresponding to the index of the PSCI
>        PM domain provider, must be "psci".
>  
> +  edac-enabled:
> +    $ref: '/schemas/types.yaml#/definitions/flag'
> +    description:
> +      Some CPUs support Error Detection And Correction (EDAC) on their L1 and
> +      L2 caches. This flag marks this function as usable.
> +
>    qcom,saw:
>      $ref: '/schemas/types.yaml#/definitions/phandle'
>      description: |
> diff --git a/drivers/edac/cortex_arm64_l1_l2.c b/drivers/edac/cortex_arm64_l1_l2.c
> index 3b1e2f3ccab6..6d5355bae80c 100644
> --- a/drivers/edac/cortex_arm64_l1_l2.c
> +++ b/drivers/edac/cortex_arm64_l1_l2.c
> @@ -190,8 +190,11 @@ static int __init cortex_arm64_edac_driver_init(void)
>  	for_each_possible_cpu(cpu) {
>  		np = of_get_cpu_node(cpu, NULL);
>  
> -		if (of_match_node(cortex_arm64_edac_of_match, np))
> -			cpumask_set_cpu(cpu, &compat_mask);
> +		if (!of_match_node(cortex_arm64_edac_of_match, np))
> +			continue;
> +		if (!of_property_read_bool(np, "edac-enabled"))
> +			continue;
> +		cpumask_set_cpu(cpu, &compat_mask);

Hum, this should be in patch 1/2 of course.

Sascha

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

[PATCH 2/2] dt-bindings: arm: cpus: Add edac-enabled property

[Sascha Hauer]

Some CPUs like the Cortex-A53 and Cortex-A57 have Error Detection And
Correction (EDAC) support on their L1 and L2 caches. This is implemented
in implementation defined registers, so usage of this functionality is
not safe in virtualized environments or when EL3 already uses these
registers.
This patch adds a edac-enabled flag which can be explicitly set when
EDAC can be used.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 Documentation/devicetree/bindings/arm/cpus.yaml | 6 ++++++
 drivers/edac/cortex_arm64_l1_l2.c               | 7 +++++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/arm/cpus.yaml b/Documentation/devicetree/bindings/arm/cpus.yaml
index 26b886b20b27..74be19c0544a 100644
--- a/Documentation/devicetree/bindings/arm/cpus.yaml
+++ b/Documentation/devicetree/bindings/arm/cpus.yaml
@@ -270,6 +270,12 @@ properties:
       For PSCI based platforms, the name corresponding to the index of the PSCI
       PM domain provider, must be "psci".
 
+  edac-enabled:
+    $ref: '/schemas/types.yaml#/definitions/flag'
+    description:
+      Some CPUs support Error Detection And Correction (EDAC) on their L1 and
+      L2 caches. This flag marks this function as usable.
+
   qcom,saw:
     $ref: '/schemas/types.yaml#/definitions/phandle'
     description: |
diff --git a/drivers/edac/cortex_arm64_l1_l2.c b/drivers/edac/cortex_arm64_l1_l2.c
index 3b1e2f3ccab6..6d5355bae80c 100644
--- a/drivers/edac/cortex_arm64_l1_l2.c
+++ b/drivers/edac/cortex_arm64_l1_l2.c
@@ -190,8 +190,11 @@ static int __init cortex_arm64_edac_driver_init(void)
 	for_each_possible_cpu(cpu) {
 		np = of_get_cpu_node(cpu, NULL);
 
-		if (of_match_node(cortex_arm64_edac_of_match, np))
-			cpumask_set_cpu(cpu, &compat_mask);
+		if (!of_match_node(cortex_arm64_edac_of_match, np))
+			continue;
+		if (!of_property_read_bool(np, "edac-enabled"))
+			continue;
+		cpumask_set_cpu(cpu, &compat_mask);
 	}
 
 	if (cpumask_empty(&compat_mask))
-- 
2.29.2

Re: [PATCH 2/2] dt-bindings: arm: cpus: Add edac-enabled property

[Marc Zyngier]

On Thu, 01 Apr 2021 12:06:15 +0100,
Sascha Hauer <s.hauer@pengutronix.de> wrote:
> 
> Some CPUs like the Cortex-A53 and Cortex-A57 have Error Detection And
> Correction (EDAC) support on their L1 and L2 caches. This is implemented
> in implementation defined registers, so usage of this functionality is
> not safe in virtualized environments or when EL3 already uses these
> registers.
> This patch adds a edac-enabled flag which can be explicitly set when
> EDAC can be used.
> 
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
>  Documentation/devicetree/bindings/arm/cpus.yaml | 6 ++++++
>  drivers/edac/cortex_arm64_l1_l2.c               | 7 +++++--
>  2 files changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/arm/cpus.yaml b/Documentation/devicetree/bindings/arm/cpus.yaml
> index 26b886b20b27..74be19c0544a 100644
> --- a/Documentation/devicetree/bindings/arm/cpus.yaml
> +++ b/Documentation/devicetree/bindings/arm/cpus.yaml
> @@ -270,6 +270,12 @@ properties:
>        For PSCI based platforms, the name corresponding to the index of the PSCI
>        PM domain provider, must be "psci".
>  
> +  edac-enabled:
> +    $ref: '/schemas/types.yaml#/definitions/flag'
> +    description:
> +      Some CPUs support Error Detection And Correction (EDAC) on their L1 and
> +      L2 caches. This flag marks this function as usable.
> +
>    qcom,saw:
>      $ref: '/schemas/types.yaml#/definitions/phandle'
>      description: |
> diff --git a/drivers/edac/cortex_arm64_l1_l2.c b/drivers/edac/cortex_arm64_l1_l2.c
> index 3b1e2f3ccab6..6d5355bae80c 100644
> --- a/drivers/edac/cortex_arm64_l1_l2.c
> +++ b/drivers/edac/cortex_arm64_l1_l2.c
> @@ -190,8 +190,11 @@ static int __init cortex_arm64_edac_driver_init(void)
>  	for_each_possible_cpu(cpu) {
>  		np = of_get_cpu_node(cpu, NULL);
>  
> -		if (of_match_node(cortex_arm64_edac_of_match, np))
> -			cpumask_set_cpu(cpu, &compat_mask);
> +		if (!of_match_node(cortex_arm64_edac_of_match, np))
> +			continue;
> +		if (!of_property_read_bool(np, "edac-enabled"))
> +			continue;
> +		cpumask_set_cpu(cpu, &compat_mask);
>  	}
>  
>  	if (cpumask_empty(&compat_mask))

This last hunk must be part of the initial patch. Otherwise, it breaks
exactly as described in the commit message.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

[PATCH 2/2] dt-bindings: arm: cpus: Add edac-enabled property

[Vijay Balakrishna]

From: Sascha Hauer <s.hauer@pengutronix.de>

Some ARM Cortex CPUs like the A53, A57 and A72 have Error Detection And
Correction (EDAC) support on their L1 and L2 caches. This is implemented
in implementation defined registers, so usage of this functionality is
not safe in virtualized environments or when EL3 already uses these
registers. This patch adds a edac-enabled flag which can be explicitly
set when EDAC can be used.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
[vijayb: Added A72 to the commit message]
Signed-off-by: Vijay Balakrishna <vijayb@linux.microsoft.com>
---
 Documentation/devicetree/bindings/arm/cpus.yaml | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/arm/cpus.yaml b/Documentation/devicetree/bindings/arm/cpus.yaml
index 2e666b2a4dcd..18d649a18552 100644
--- a/Documentation/devicetree/bindings/arm/cpus.yaml
+++ b/Documentation/devicetree/bindings/arm/cpus.yaml
@@ -331,6 +331,12 @@ properties:
       corresponding to the index of an SCMI performance domain provider, must be
       "perf".
 
+  edac-enabled:
+    $ref: '/schemas/types.yaml#/definitions/flag'
+    description:
+      Some CPUs support Error Detection And Correction (EDAC) on their L1 and
+      L2 caches. This flag marks this function as usable.
+
   qcom,saw:
     $ref: /schemas/types.yaml#/definitions/phandle
     description: |
-- 
2.49.0

Re: [PATCH 2/2] dt-bindings: arm: cpus: Add edac-enabled property

[Krzysztof Kozlowski]

On 10/04/2025 01:36, Vijay Balakrishna wrote:
> From: Sascha Hauer <s.hauer@pengutronix.de>
> 
> Some ARM Cortex CPUs like the A53, A57 and A72 have Error Detection And
> Correction (EDAC) support on their L1 and L2 caches. This is implemented
> in implementation defined registers, so usage of this functionality is
> not safe in virtualized environments or when EL3 already uses these
> registers. This patch adds a edac-enabled flag which can be explicitly
> set when EDAC can be used.

Can't hypervisor tell you that?

> 
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> [vijayb: Added A72 to the commit message]
> Signed-off-by: Vijay Balakrishna <vijayb@linux.microsoft.com>
> ---
>  Documentation/devicetree/bindings/arm/cpus.yaml | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/arm/cpus.yaml b/Documentation/devicetree/bindings/arm/cpus.yaml
> index 2e666b2a4dcd..18d649a18552 100644
> --- a/Documentation/devicetree/bindings/arm/cpus.yaml
> +++ b/Documentation/devicetree/bindings/arm/cpus.yaml
> @@ -331,6 +331,12 @@ properties:
>        corresponding to the index of an SCMI performance domain provider, must be
>        "perf".
>  
> +  edac-enabled:
> +    $ref: '/schemas/types.yaml#/definitions/flag'

Drop quotes - look at every other line.

<form letter>
Please use scripts/get_maintainers.pl to get a list of necessary people
and lists to CC. It might happen, that command when run on an older
kernel, gives you outdated entries. Therefore please be sure you base
your patches on recent Linux kernel.

Tools like b4 or scripts/get_maintainer.pl provide you proper list of
people, so fix your workflow. Tools might also fail if you work on some
ancient tree (don't, instead use mainline) or work on fork of kernel
(don't, instead use mainline). Just use b4 and everything should be
fine, although remember about `b4 prep --auto-to-cc` if you added new
patches to the patchset.

You missed at least devicetree list (maybe more), so this won't be
tested by automated tooling. Performing review on untested code might be
a waste of time.

Please kindly resend and include all necessary To/Cc entries.
</form letter>



Best regards,
Krzysztof

Re: [PATCH 2/2] dt-bindings: arm: cpus: Add edac-enabled property

[Marc Zyngier]

On Thu, 10 Apr 2025 07:00:55 +0100,
Krzysztof Kozlowski <krzk@kernel.org> wrote:
> 
> On 10/04/2025 01:36, Vijay Balakrishna wrote:
> > From: Sascha Hauer <s.hauer@pengutronix.de>
> > 
> > Some ARM Cortex CPUs like the A53, A57 and A72 have Error Detection And
> > Correction (EDAC) support on their L1 and L2 caches. This is implemented
> > in implementation defined registers, so usage of this functionality is
> > not safe in virtualized environments or when EL3 already uses these
> > registers. This patch adds a edac-enabled flag which can be explicitly
> > set when EDAC can be used.
> 
> Can't hypervisor tell you that?

No, it can't. This is not an architecture feature, and KVM will gladly
inject an UNDEF exception if the guest tries to use this.

Which is yet another reason why this whole exercise is futile.

	M.

-- 
Without deviation from the norm, progress is not possible.

Re: [PATCH 2/2] dt-bindings: arm: cpus: Add edac-enabled property

[Tyler Hicks (Microsoft)]

On 2025-04-10 08:10:18, Marc Zyngier wrote:
> On Thu, 10 Apr 2025 07:00:55 +0100,
> Krzysztof Kozlowski <krzk@kernel.org> wrote:
> > 
> > On 10/04/2025 01:36, Vijay Balakrishna wrote:
> > > From: Sascha Hauer <s.hauer@pengutronix.de>
> > > 
> > > Some ARM Cortex CPUs like the A53, A57 and A72 have Error Detection And
> > > Correction (EDAC) support on their L1 and L2 caches. This is implemented
> > > in implementation defined registers, so usage of this functionality is
> > > not safe in virtualized environments or when EL3 already uses these
> > > registers. This patch adds a edac-enabled flag which can be explicitly
> > > set when EDAC can be used.
> > 
> > Can't hypervisor tell you that?
> 
> No, it can't. This is not an architecture feature, and KVM will gladly
> inject an UNDEF exception if the guest tries to use this.
> 
> Which is yet another reason why this whole exercise is futile.

Hi Marc - could you clarify why this is futile for baremetal or were you just
referring to virtualized environments?

Thanks!

Tyler

> 
> 	M.
> 
> -- 
> Without deviation from the norm, progress is not possible.

Re: [PATCH 2/2] dt-bindings: arm: cpus: Add edac-enabled property

[Marc Zyngier]

On Thu, 10 Apr 2025 15:30:17 +0100,
"Tyler Hicks (Microsoft)" <code@tyhicks.com> wrote:
> 
> On 2025-04-10 08:10:18, Marc Zyngier wrote:
> > On Thu, 10 Apr 2025 07:00:55 +0100,
> > Krzysztof Kozlowski <krzk@kernel.org> wrote:
> > > 
> > > On 10/04/2025 01:36, Vijay Balakrishna wrote:
> > > > From: Sascha Hauer <s.hauer@pengutronix.de>
> > > > 
> > > > Some ARM Cortex CPUs like the A53, A57 and A72 have Error Detection And
> > > > Correction (EDAC) support on their L1 and L2 caches. This is implemented
> > > > in implementation defined registers, so usage of this functionality is
> > > > not safe in virtualized environments or when EL3 already uses these
> > > > registers. This patch adds a edac-enabled flag which can be explicitly
> > > > set when EDAC can be used.
> > > 
> > > Can't hypervisor tell you that?
> > 
> > No, it can't. This is not an architecture feature, and KVM will gladly
> > inject an UNDEF exception if the guest tries to use this.
> > 
> > Which is yet another reason why this whole exercise is futile.
> 
> Hi Marc - could you clarify why this is futile for baremetal or were you just
> referring to virtualized environments?

This is futile in general. This sort of stuff only makes sense if you
can take useful action upon detecting an error, such as cache
scrubbing. Here, this is just telling you "bang, you're dead", without
any other recourse. You are not even sure you'll be able to actually
*run* this code. You cannot identify what the blast radius.

We have some other EDAC implementation for arm64 CPUs (XGene,
ThunderX), and they are all perfectly useless (I have them in my
collection of horrors). I know you are familiar enough with the RAS
architecture to appreciate the difference with a contemporary
implementation that would actually do the right thing.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

Re: [PATCH 2/2] dt-bindings: arm: cpus: Add edac-enabled property

[Tyler Hicks (Microsoft)]

On 2025-04-10 17:23:26, Marc Zyngier wrote:
> On Thu, 10 Apr 2025 15:30:17 +0100,
> "Tyler Hicks (Microsoft)" <code@tyhicks.com> wrote:
> > 
> > On 2025-04-10 08:10:18, Marc Zyngier wrote:
> > > On Thu, 10 Apr 2025 07:00:55 +0100,
> > > Krzysztof Kozlowski <krzk@kernel.org> wrote:
> > > > 
> > > > On 10/04/2025 01:36, Vijay Balakrishna wrote:
> > > > > From: Sascha Hauer <s.hauer@pengutronix.de>
> > > > > 
> > > > > Some ARM Cortex CPUs like the A53, A57 and A72 have Error Detection And
> > > > > Correction (EDAC) support on their L1 and L2 caches. This is implemented
> > > > > in implementation defined registers, so usage of this functionality is
> > > > > not safe in virtualized environments or when EL3 already uses these
> > > > > registers. This patch adds a edac-enabled flag which can be explicitly
> > > > > set when EDAC can be used.
> > > > 
> > > > Can't hypervisor tell you that?
> > > 
> > > No, it can't. This is not an architecture feature, and KVM will gladly
> > > inject an UNDEF exception if the guest tries to use this.
> > > 
> > > Which is yet another reason why this whole exercise is futile.
> > 
> > Hi Marc - could you clarify why this is futile for baremetal or were you just
> > referring to virtualized environments?
> 
> This is futile in general. This sort of stuff only makes sense if you
> can take useful action upon detecting an error, such as cache
> scrubbing. Here, this is just telling you "bang, you're dead", without
> any other recourse. You are not even sure you'll be able to actually
> *run* this code. You cannot identify what the blast radius.

We want to use it for monitoring purposes to let us know when a system needs to
be replaced. Knowing the number of Correctable Errors that a specific system is
encountering will help prioritize the replacement of that faulty system.

Also, if we can find some breadcrumbs of an Uncorrectable Error (UE) occurring
just before an important process crashes or before the kernel crashing, then we
can avoid expensive manual debugging and simply replace the system. Automation
can be implemented to dig through the kernel core dump contents to look for a
UE log message from this driver and a kernel engineer will never have to look
at the dump.

> We have some other EDAC implementation for arm64 CPUs (XGene,
> ThunderX), and they are all perfectly useless (I have them in my
> collection of horrors). I know you are familiar enough with the RAS
> architecture to appreciate the difference with a contemporary
> implementation that would actually do the right thing.

Yes, those are nice luxuries to have in the newer implementations but there are
still a lot of older systems in use and making do with what capabilities the
older hardware provides is still useful.

Tyler

> 
> Thanks,
> 
> 	M.
> 
> -- 
> Without deviation from the norm, progress is not possible.

Re: [PATCH 2/2] dt-bindings: arm: cpus: Add edac-enabled property

[Borislav Petkov]

On Thu, Apr 10, 2025 at 05:23:26PM +0100, Marc Zyngier wrote:
> We have some other EDAC implementation for arm64 CPUs (XGene,
> ThunderX), and they are all perfectly useless (I have them in my
> collection of horrors).

Oh oh, can I remove, can I remove?

My trigger finger is itching to kill some more useless code...

Thx.

[PATCH 2/2] dt-bindings: arm: cpus: Add edac-enabled property

[Vijay Balakrishna]

From: Sascha Hauer <s.hauer@pengutronix.de>

Some ARM Cortex CPUs like the A53, A57 and A72 have Error Detection And
Correction (EDAC) support on their L1 and L2 caches. This is implemented
in implementation defined registers, so usage of this functionality is
not safe in virtualized environments or when EL3 already uses these
registers. This patch adds a edac-enabled flag which can be explicitly
set when EDAC can be used.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
[vijayb: Added A72 to the commit message]
Signed-off-by: Vijay Balakrishna <vijayb@linux.microsoft.com>
---
 Documentation/devicetree/bindings/arm/cpus.yaml | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/arm/cpus.yaml b/Documentation/devicetree/bindings/arm/cpus.yaml
index 2e666b2a4dcd..d1dc0a843d07 100644
--- a/Documentation/devicetree/bindings/arm/cpus.yaml
+++ b/Documentation/devicetree/bindings/arm/cpus.yaml
@@ -331,6 +331,12 @@ properties:
       corresponding to the index of an SCMI performance domain provider, must be
       "perf".
 
+  edac-enabled:
+    $ref: /schemas/types.yaml#/definitions/flag
+    description:
+      Some CPUs support Error Detection And Correction (EDAC) on their L1 and
+      L2 caches. This flag marks this function as usable.
+
   qcom,saw:
     $ref: /schemas/types.yaml#/definitions/phandle
     description: |
-- 
2.49.0

Re: [PATCH 2/2] dt-bindings: arm: cpus: Add edac-enabled property

[Marc Zyngier]

On Fri, 11 Apr 2025 21:02:07 +0100,
Borislav Petkov <bp@alien8.de> wrote:
> 
> On Thu, Apr 10, 2025 at 05:23:26PM +0100, Marc Zyngier wrote:
> > We have some other EDAC implementation for arm64 CPUs (XGene,
> > ThunderX), and they are all perfectly useless (I have them in my
> > collection of horrors).
> 
> Oh oh, can I remove, can I remove?
> 
> My trigger finger is itching to kill some more useless code...

The drivers do report ECC errors being corrected, which indicates that
the HW itself is doing its job. Yes, I buy cheap memory from eBay.

Do we need actual drivers to output crap on the console? Probably not,
but I'm the wrong person to ask -- I only keep these machines alive to
remind me how things can go horribly wrong.

I don't think there is any harm in keeping this crap around. It
compiles, and if it breaks, I'll fix it. I'm not convinced we need any
more of it though, specially for CPUs that are over a decade old.

	M.

-- 
Without deviation from the norm, progress is not possible.

[PATCH 2/2] dt-bindings: arm: cpus: Add edac-enabled property

[Vijay Balakrishna]

From: Sascha Hauer <s.hauer@pengutronix.de>

Some ARM Cortex CPUs like the A53, A57 and A72 have Error Detection And
Correction (EDAC) support on their L1 and L2 caches. This is implemented
in implementation defined registers, so usage of this functionality is
not safe in virtualized environments or when EL3 already uses these
registers. This patch adds a edac-enabled flag which can be explicitly
set when EDAC can be used.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
[vijayb: Added A72 to the commit message]
Signed-off-by: Vijay Balakrishna <vijayb@linux.microsoft.com>
---
 Documentation/devicetree/bindings/arm/cpus.yaml | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/arm/cpus.yaml b/Documentation/devicetree/bindings/arm/cpus.yaml
index 2e666b2a4dcd..d1dc0a843d07 100644
--- a/Documentation/devicetree/bindings/arm/cpus.yaml
+++ b/Documentation/devicetree/bindings/arm/cpus.yaml
@@ -331,6 +331,12 @@ properties:
       corresponding to the index of an SCMI performance domain provider, must be
       "perf".
 
+  edac-enabled:
+    $ref: /schemas/types.yaml#/definitions/flag
+    description:
+      Some CPUs support Error Detection And Correction (EDAC) on their L1 and
+      L2 caches. This flag marks this function as usable.
+
   qcom,saw:
     $ref: /schemas/types.yaml#/definitions/phandle
     description: |
-- 
2.49.0

Re: [PATCH 2/2] dt-bindings: arm: cpus: Add edac-enabled property

[Rob Herring]

On Sun, May 04, 2025 at 05:27:40PM -0700, Vijay Balakrishna wrote:
> From: Sascha Hauer <s.hauer@pengutronix.de>
> 
> Some ARM Cortex CPUs like the A53, A57 and A72 have Error Detection And
> Correction (EDAC) support on their L1 and L2 caches. This is implemented
> in implementation defined registers, so usage of this functionality is
> not safe in virtualized environments or when EL3 already uses these
> registers. This patch adds a edac-enabled flag which can be explicitly
> set when EDAC can be used.
> 
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> [vijayb: Added A72 to the commit message]
> Signed-off-by: Vijay Balakrishna <vijayb@linux.microsoft.com>
> ---
>  Documentation/devicetree/bindings/arm/cpus.yaml | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/arm/cpus.yaml b/Documentation/devicetree/bindings/arm/cpus.yaml
> index 2e666b2a4dcd..d1dc0a843d07 100644
> --- a/Documentation/devicetree/bindings/arm/cpus.yaml
> +++ b/Documentation/devicetree/bindings/arm/cpus.yaml
> @@ -331,6 +331,12 @@ properties:
>        corresponding to the index of an SCMI performance domain provider, must be
>        "perf".
>  
> +  edac-enabled:
> +    $ref: /schemas/types.yaml#/definitions/flag
> +    description:
> +      Some CPUs support Error Detection And Correction (EDAC) on their L1 and
> +      L2 caches. This flag marks this function as usable.
> +

Since we don't want this on newer cores, add an if/then schema to only 
allow this on A72 and whatever else you end up supporting.

Rob