EDAC: Add a Error Check Scrub control feature

Add an Error Check Scrub (ECS) control to manage a memory device's ECS
feature.

The ECS is a feature defined in JEDEC DDR5 SDRAM Specification (JESD79-5) and
allows the DRAM to internally read, correct single-bit errors, and write back
corrected data bits to the DRAM array while providing transparency to error
counts.

The DDR5 device contains a number of memory media Field Replaceable Units
(FRU) per device. The DDR5 ECS feature and thus the ECS control driver
supports configuring the ECS parameters per FRU.

Memory devices support the ECS feature register with the EDAC device driver,
which retrieves the ECS descriptor from the EDAC ECS driver. This driver
exposes sysfs ECS control attributes to userspace via

/sys/bus/edac/devices/<dev-name>/ecs_fruX/.

The common sysfs ECS control interface abstracts the control of an arbitrary
ECS functionality to a common set of functions.

Support for the ECS feature is added separately because the control attributes
of the DDR5 ECS feature differ from those of the scrub feature.

The sysfs ECS attribute nodes are only present if the client driver has
implemented the corresponding attribute callback function and passed the
necessary operations to the EDAC RAS feature driver during registration.

[ bp: Massage, fixup edac_dev_register() retvals. ]

Co-developed-by: Jonathan Cameron <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>
Signed-off-by: Shiju Jose <[e-mail]>
Signed-off-by: Borislav Petkov (AMD) <[e-mail]>
Reviewed-by: Fan Ni <[e-mail]>
Tested-by: Fan Ni <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

Documentation/ABI/testing/sysfs-edac-ecs

···
+What:		/sys/bus/edac/devices/<dev-name>/ecs_fruX
+Date:		March 2025
+KernelVersion:	6.15
+Contact:	[e-mail]
+Description:
+		The sysfs EDAC bus devices /<dev-name>/ecs_fruX subdirectory
+		pertains to the memory media ECS (Error Check Scrub) control
+		feature, where <dev-name> directory corresponds to a device
+		registered with the EDAC device driver for the ECS feature.
+		/ecs_fruX belongs to the media FRUs (Field Replaceable Unit)
+		under the memory device.
+
+		The sysfs ECS attr nodes are only present if the parent
+		driver has implemented the corresponding attr callback
+		function and provided the necessary operations to the EDAC
+		device driver during registration.
+
+What:		/sys/bus/edac/devices/<dev-name>/ecs_fruX/log_entry_type
+Date:		March 2025
+KernelVersion:	6.15
+Contact:	[e-mail]
+Description:
+		(RW) The log entry type of how the DDR5 ECS log is reported.
+
+		- 0 - per DRAM.
+
+		- 1 - per memory media FRU.
+
+		- All other values are reserved.
+
+What:		/sys/bus/edac/devices/<dev-name>/ecs_fruX/mode
+Date:		March 2025
+KernelVersion:	6.15
+Contact:	[e-mail]
+Description:
+		(RW) The mode of how the DDR5 ECS counts the errors.
+		Error count is tracked based on two different modes
+		selected by DDR5 ECS Control Feature - Codeword mode and
+		Row Count mode. If the ECS is under Codeword mode, then
+		the error count increments each time a codeword with check
+		bit errors is detected. If the ECS is under Row Count mode,
+		then the error counter increments each time a row with
+		check bit errors is detected.
+
+		- 0 - ECS counts rows in the memory media that have ECC errors.
+
+		- 1 - ECS counts codewords with errors, specifically, it counts
+		      the number of ECC-detected errors in the memory media.
+
+		- All other values are reserved.
+
+What:		/sys/bus/edac/devices/<dev-name>/ecs_fruX/reset
+Date:		March 2025
+KernelVersion:	6.15
+Contact:	[e-mail]
+Description:
+		(WO) ECS reset ECC counter.
+
+		- 1 - reset ECC counter to the default value.
+
+		- All other values are reserved.
+
+What:		/sys/bus/edac/devices/<dev-name>/ecs_fruX/threshold
+Date:		March 2025
+KernelVersion:	6.15
+Contact:	[e-mail]
+Description:
+		(RW) DDR5 ECS threshold count per gigabits of memory cells.
+		The ECS error count is subject to the ECS Threshold count
+		per Gbit, which masks error counts less than the Threshold.
+
+		Supported values are 256, 1024 and 4096.
+
+		All other values are reserved.

Documentation/edac/scrub.rst

···
 
 Sysfs files are documented in
 `Documentation/ABI/testing/sysfs-edac-scrub`
+
+`Documentation/ABI/testing/sysfs-edac-ecs`

drivers/edac/Kconfig

···
 	  into a unified set of functions.
 	  Say 'y/n' to enable/disable EDAC scrub feature.
 
+config EDAC_ECS
+	bool "EDAC ECS (Error Check Scrub) feature"
+	help
+	  The EDAC ECS feature is optional and is designed to control on-die
+	  error check scrub (e.g., DDR5 ECS) in the system. The common sysfs
+	  ECS interface abstracts the control of various ECS functionalities
+	  into a unified set of functions.
+	  Say 'y/n' to enable/disable EDAC ECS feature.
+
 config EDAC_AMD64
 	tristate "AMD64 (Opteron, Athlon64)"
 	depends on AMD_NB && EDAC_DECODE_MCE

drivers/edac/Makefile

···
 
 edac_core-$(CONFIG_EDAC_DEBUG)		+= debugfs.o
 edac_core-$(CONFIG_EDAC_SCRUB)		+= scrub.o
+edac_core-$(CONFIG_EDAC_ECS)		+= ecs.o
 
 ifdef CONFIG_PCI
 edac_core-y	+= edac_pci.o edac_pci_sysfs.o

drivers/edac/ecs.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * The generic ECS driver is designed to support control of on-die error
+ * check scrub (e.g., DDR5 ECS). The common sysfs ECS interface abstracts
+ * the control of various ECS functionalities into a unified set of functions.
+ *
+ * Copyright (c) 2024-2025 HiSilicon Limited.
+ */
+
+#include <linux/edac.h>
+
+#define EDAC_ECS_FRU_NAME "ecs_fru"
+
+enum edac_ecs_attributes {
+	ECS_LOG_ENTRY_TYPE,
+	ECS_MODE,
+	ECS_RESET,
+	ECS_THRESHOLD,
+	ECS_MAX_ATTRS
+};
+
+struct edac_ecs_dev_attr {
+	struct device_attribute dev_attr;
+	int fru_id;
+};
+
+struct edac_ecs_fru_context {
+	char name[EDAC_FEAT_NAME_LEN];
+	struct edac_ecs_dev_attr dev_attr[ECS_MAX_ATTRS];
+	struct attribute *ecs_attrs[ECS_MAX_ATTRS + 1];
+	struct attribute_group group;
+};
+
+struct edac_ecs_context {
+	u16 num_media_frus;
+	struct edac_ecs_fru_context *fru_ctxs;
+};
+
+#define TO_ECS_DEV_ATTR(_dev_attr)	\
+	container_of(_dev_attr, struct edac_ecs_dev_attr, dev_attr)
+
+#define EDAC_ECS_ATTR_SHOW(attrib, cb, type, format)				\
+static ssize_t attrib##_show(struct device *ras_feat_dev,			\
+			     struct device_attribute *attr, char *buf)		\
+{										\
+	struct edac_ecs_dev_attr *dev_attr = TO_ECS_DEV_ATTR(attr);		\
+	struct edac_dev_feat_ctx *ctx = dev_get_drvdata(ras_feat_dev);		\
+	const struct edac_ecs_ops *ops = ctx->ecs.ecs_ops;			\
+	type data;								\
+	int ret;								\
+										\
+	ret = ops->cb(ras_feat_dev->parent, ctx->ecs.private,			\
+		      dev_attr->fru_id, &data);					\
+	if (ret)								\
+		return ret;							\
+										\
+	return sysfs_emit(buf, format, data);					\
+}
+
+EDAC_ECS_ATTR_SHOW(log_entry_type, get_log_entry_type, u32, "%u\n")
+EDAC_ECS_ATTR_SHOW(mode, get_mode, u32, "%u\n")
+EDAC_ECS_ATTR_SHOW(threshold, get_threshold, u32, "%u\n")
+
+#define EDAC_ECS_ATTR_STORE(attrib, cb, type, conv_func)			\
+static ssize_t attrib##_store(struct device *ras_feat_dev,			\
+			      struct device_attribute *attr,			\
+			      const char *buf, size_t len)			\
+{										\
+	struct edac_ecs_dev_attr *dev_attr = TO_ECS_DEV_ATTR(attr);		\
+	struct edac_dev_feat_ctx *ctx = dev_get_drvdata(ras_feat_dev);		\
+	const struct edac_ecs_ops *ops = ctx->ecs.ecs_ops;			\
+	type data;								\
+	int ret;								\
+										\
+	ret = conv_func(buf, 0, &data);						\
+	if (ret < 0)								\
+		return ret;							\
+										\
+	ret = ops->cb(ras_feat_dev->parent, ctx->ecs.private,			\
+		      dev_attr->fru_id, data);					\
+	if (ret)								\
+		return ret;							\
+										\
+	return len;								\
+}
+
+EDAC_ECS_ATTR_STORE(log_entry_type, set_log_entry_type, unsigned long, kstrtoul)
+EDAC_ECS_ATTR_STORE(mode, set_mode, unsigned long, kstrtoul)
+EDAC_ECS_ATTR_STORE(reset, reset, unsigned long, kstrtoul)
+EDAC_ECS_ATTR_STORE(threshold, set_threshold, unsigned long, kstrtoul)
+
+static umode_t ecs_attr_visible(struct kobject *kobj, struct attribute *a, int attr_id)
+{
+	struct device *ras_feat_dev = kobj_to_dev(kobj);
+	struct edac_dev_feat_ctx *ctx = dev_get_drvdata(ras_feat_dev);
+	const struct edac_ecs_ops *ops = ctx->ecs.ecs_ops;
+
+	switch (attr_id) {
+	case ECS_LOG_ENTRY_TYPE:
+		if (ops->get_log_entry_type)  {
+			if (ops->set_log_entry_type)
+				return a->mode;
+			else
+				return 0444;
+		}
+		break;
+	case ECS_MODE:
+		if (ops->get_mode) {
+			if (ops->set_mode)
+				return a->mode;
+			else
+				return 0444;
+		}
+		break;
+	case ECS_RESET:
+		if (ops->reset)
+			return a->mode;
+		break;
+	case ECS_THRESHOLD:
+		if (ops->get_threshold) {
+			if (ops->set_threshold)
+				return a->mode;
+			else
+				return 0444;
+		}
+		break;
+	default:
+		break;
+	}
+
+	return 0;
+}
+
+#define EDAC_ECS_ATTR_RO(_name, _fru_id)       \
+	((struct edac_ecs_dev_attr) { .dev_attr = __ATTR_RO(_name), \
+				     .fru_id = _fru_id })
+
+#define EDAC_ECS_ATTR_WO(_name, _fru_id)       \
+	((struct edac_ecs_dev_attr) { .dev_attr = __ATTR_WO(_name), \
+				     .fru_id = _fru_id })
+
+#define EDAC_ECS_ATTR_RW(_name, _fru_id)       \
+	((struct edac_ecs_dev_attr) { .dev_attr = __ATTR_RW(_name), \
+				     .fru_id = _fru_id })
+
+static int ecs_create_desc(struct device *ecs_dev, const struct attribute_group **attr_groups,
+			   u16 num_media_frus)
+{
+	struct edac_ecs_context *ecs_ctx;
+	u32 fru;
+
+	ecs_ctx = devm_kzalloc(ecs_dev, sizeof(*ecs_ctx), GFP_KERNEL);
+	if (!ecs_ctx)
+		return -ENOMEM;
+
+	ecs_ctx->num_media_frus = num_media_frus;
+	ecs_ctx->fru_ctxs = devm_kcalloc(ecs_dev, num_media_frus,
+					 sizeof(*ecs_ctx->fru_ctxs),
+					 GFP_KERNEL);
+	if (!ecs_ctx->fru_ctxs)
+		return -ENOMEM;
+
+	for (fru = 0; fru < num_media_frus; fru++) {
+		struct edac_ecs_fru_context *fru_ctx = &ecs_ctx->fru_ctxs[fru];
+		struct attribute_group *group = &fru_ctx->group;
+		int i;
+
+		fru_ctx->dev_attr[ECS_LOG_ENTRY_TYPE]	= EDAC_ECS_ATTR_RW(log_entry_type, fru);
+		fru_ctx->dev_attr[ECS_MODE]		= EDAC_ECS_ATTR_RW(mode, fru);
+		fru_ctx->dev_attr[ECS_RESET]		= EDAC_ECS_ATTR_WO(reset, fru);
+		fru_ctx->dev_attr[ECS_THRESHOLD]	= EDAC_ECS_ATTR_RW(threshold, fru);
+
+		for (i = 0; i < ECS_MAX_ATTRS; i++)
+			fru_ctx->ecs_attrs[i] = &fru_ctx->dev_attr[i].dev_attr.attr;
+
+		sprintf(fru_ctx->name, "%s%d", EDAC_ECS_FRU_NAME, fru);
+		group->name = fru_ctx->name;
+		group->attrs = fru_ctx->ecs_attrs;
+		group->is_visible  = ecs_attr_visible;
+
+		attr_groups[fru] = group;
+	}
+
+	return 0;
+}
+
+/**
+ * edac_ecs_get_desc - get EDAC ECS descriptors
+ * @ecs_dev: client device, supports ECS feature
+ * @attr_groups: pointer to attribute group container
+ * @num_media_frus: number of media FRUs in the device
+ *
+ * Return:
+ *  * %0	- Success.
+ *  * %-EINVAL	- Invalid parameters passed.
+ *  * %-ENOMEM	- Dynamic memory allocation failed.
+ */
+int edac_ecs_get_desc(struct device *ecs_dev,
+		      const struct attribute_group **attr_groups, u16 num_media_frus)
+{
+	if (!ecs_dev || !attr_groups || !num_media_frus)
+		return -EINVAL;
+
+	return ecs_create_desc(ecs_dev, attr_groups, num_media_frus);
+}

drivers/edac/edac_device.c

···
 			attr_gcnt++;
 			scrub_cnt++;
 			break;
+		case RAS_FEAT_ECS:
+			attr_gcnt += ras_features[feat].ecs_info.num_media_frus;
+			break;
 		default:
 			return -EINVAL;
 		}
···
 
 			scrub_cnt++;
 			attr_gcnt++;
+			break;
+		case RAS_FEAT_ECS:
+			if (!ras_features->ecs_ops) {
+				ret = -EINVAL;
+				goto data_mem_free;
+			}
+
+			dev_data = &ctx->ecs;
+			dev_data->ecs_ops = ras_features->ecs_ops;
+			dev_data->private = ras_features->ctx;
+			ret = edac_ecs_get_desc(parent, &ras_attr_groups[attr_gcnt],
+						ras_features->ecs_info.num_media_frus);
+			if (ret)
+				goto data_mem_free;
+
+			attr_gcnt += ras_features->ecs_info.num_media_frus;
 			break;
 		default:
 			ret = -EINVAL;

include/linux/edac.h

···
 /* RAS feature type */
 enum edac_dev_feat {
 	RAS_FEAT_SCRUB,
+	RAS_FEAT_ECS,
 	RAS_FEAT_MAX
 };
 
···
 { return -EOPNOTSUPP; }
 #endif /* CONFIG_EDAC_SCRUB */
 
+/**
+ * struct edac_ecs_ops - ECS device operations (all elements optional)
+ * @get_log_entry_type: read the log entry type value.
+ * @set_log_entry_type: set the log entry type value.
+ * @get_mode: read the mode value.
+ * @set_mode: set the mode value.
+ * @reset: reset the ECS counter.
+ * @get_threshold: read the threshold count per gigabits of memory cells.
+ * @set_threshold: set the threshold count per gigabits of memory cells.
+ */
+struct edac_ecs_ops {
+	int (*get_log_entry_type)(struct device *dev, void *drv_data, int fru_id, u32 *val);
+	int (*set_log_entry_type)(struct device *dev, void *drv_data, int fru_id, u32 val);
+	int (*get_mode)(struct device *dev, void *drv_data, int fru_id, u32 *val);
+	int (*set_mode)(struct device *dev, void *drv_data, int fru_id, u32 val);
+	int (*reset)(struct device *dev, void *drv_data, int fru_id, u32 val);
+	int (*get_threshold)(struct device *dev, void *drv_data, int fru_id, u32 *threshold);
+	int (*set_threshold)(struct device *dev, void *drv_data, int fru_id, u32 threshold);
+};
+
+struct edac_ecs_ex_info {
+	u16 num_media_frus;
+};
+
+#if IS_ENABLED(CONFIG_EDAC_ECS)
+int edac_ecs_get_desc(struct device *ecs_dev,
+		      const struct attribute_group **attr_groups,
+		      u16 num_media_frus);
+#else
+static inline int edac_ecs_get_desc(struct device *ecs_dev,
+				    const struct attribute_group **attr_groups,
+				    u16 num_media_frus)
+{ return -EOPNOTSUPP; }
+#endif /* CONFIG_EDAC_ECS */
+
 /* EDAC device feature information structure */
 struct edac_dev_data {
-	const struct edac_scrub_ops *scrub_ops;
+	union {
+		const struct edac_scrub_ops *scrub_ops;
+		const struct edac_ecs_ops *ecs_ops;
+	};
 	u8 instance;
 	void *private;
 };
···
 	struct device dev;
 	void *private;
 	struct edac_dev_data *scrub;
+	struct edac_dev_data ecs;
 };
 
 struct edac_dev_feature {
 	enum edac_dev_feat ft_type;
 	u8 instance;
-	const struct edac_scrub_ops *scrub_ops;
+	union {
+		const struct edac_scrub_ops *scrub_ops;
+		const struct edac_ecs_ops *ecs_ops;
+	};
 	void *ctx;
+	struct edac_ecs_ex_info ecs_info;
 };
 
 int edac_dev_register(struct device *parent, char *dev_name,