RE: [RFC PATCH 2/6] cxl/memscrub: Add CXL device patrol scrub control feature

[Shiju Jose]

Hi Dave,

>-----Original Message-----
>From: Dave Jiang <dave.jiang@xxxxxxxxx>
>Sent: 15 November 2023 21:24
>To: Shiju Jose <shiju.jose@xxxxxxxxxx>; linux-cxl@xxxxxxxxxxxxxxx
>Cc: Jonathan Cameron <jonathan.cameron@xxxxxxxxxx>;
>Vilas.Sridharan@xxxxxxx; leo.duran@xxxxxxx; Yazen.Ghannam@xxxxxxx;
>rientjes@xxxxxxxxxx; jiaqiyan@xxxxxxxxxx; tony.luck@xxxxxxxxx;
>Jon.Grimm@xxxxxxx; dave.hansen@xxxxxxxxxxxxxxx; linux-
>acpi@xxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
>rafael@xxxxxxxxxx; lenb@xxxxxxxxxx; naoya.horiguchi@xxxxxxx;
>james.morse@xxxxxxx; david@xxxxxxxxxx; jthoughton@xxxxxxxxxx;
>somasundaram.a@xxxxxxx; erdemaktas@xxxxxxxxxx; duenwen@xxxxxxxxxx;
>mike.malvestuto@xxxxxxxxx; gthelen@xxxxxxxxxx; tanxiaofei
><tanxiaofei@xxxxxxxxxx>; Zengtao (B) <prime.zeng@xxxxxxxxxxxxx>;
>kangkang.shen@xxxxxxxxxxxxx; wanghuiqiang <wanghuiqiang@xxxxxxxxxx>;
>Linuxarm <linuxarm@xxxxxxxxxx>
>Subject: Re: [RFC PATCH 2/6] cxl/memscrub: Add CXL device patrol scrub control
>feature
>
>
>
>On 11/14/23 05:56, shiju.jose@xxxxxxxxxx wrote:
>> From: Shiju Jose <shiju.jose@xxxxxxxxxx>
>>
>> CXL spec 3.1 section 8.2.9.9.11.1 describes the device patrol scrub
>> control feature. The device patrol scrub proactively locates and makes
>> corrections to errors in regular cycle. The patrol scrub control
>> allows the request to configure patrol scrub input configurations.
>>
>> The patrol scrub control allows the requester to specify the number of
>> hours for which the patrol scrub cycles must be completed, provided
>> that the requested number is not less than the minimum number of hours
>> for the patrol scrub cycle that the device is capable of. In addition,
>> the patrol scrub controls allow the host to disable and enable the
>> feature in case disabling of the feature is needed for other purposes
>> such as performance-aware operations which require the background
>> operations to be turned off.
>>
>> Signed-off-by: Shiju Jose <shiju.jose@xxxxxxxxxx>
>> ---
>>  drivers/cxl/Kconfig         |  23 ++
>>  drivers/cxl/core/Makefile   |   1 +
>>  drivers/cxl/core/memscrub.c | 455
>++++++++++++++++++++++++++++++++++++
>>  drivers/cxl/cxlmem.h        |   7 +
>>  drivers/cxl/pci.c           |   6 +
>>  5 files changed, 492 insertions(+)
>
>
>Maybe this patch can be split up? Awfully large. Maybe a patch with support
>functions and then another with usages?
Sure. I will check this.

>
>>  create mode 100644 drivers/cxl/core/memscrub.c
>>
>> diff --git a/drivers/cxl/Kconfig b/drivers/cxl/Kconfig index
>> 8ea1d340e438..45ee6d57d899 100644
>> --- a/drivers/cxl/Kconfig
>> +++ b/drivers/cxl/Kconfig
>> @@ -154,4 +154,27 @@ config CXL_PMU
>>  	  monitoring units and provide standard perf based interfaces.
>>
>>  	  If unsure say 'm'.
>> +
>> +config CXL_SCRUB
>> +	tristate "CXL: Memory scrub feature"
>> +	depends on CXL_PCI
>> +	depends on CXL_MEM
>> +	depends on SCRUB
>> +	help
>> +	  The CXL memory scrub control is an optional feature allows host to
>> +	  control the scrub configurations of CXL Type 3 devices, which
>> +	  support patrol scrub and/or DDR5 ECS(Error Check Scrub).
>> +
>> +	  Register with the scrub configure driver to provide sysfs interfaces
>> +	  for configuring the CXL device memory patrol and DDR5 ECS scrubs.
>> +	  Provides the interface functions support configuring the CXL memory
>> +	  device patrol and ECS scrubs.
>> +
>> +	  Say 'y/m' to enable the CXL memory scrub driver that will attach to
>> +	  CXL.mem devices for memory scrub control feature. See sections
>> +	  8.2.9.9.11.1 and 8.2.9.9.11.2 in the CXL 3.1 specification for a
>> +	  detailed description of CXL memory scrub control features.
>> +
>> +	  If unsure say 'm'.
>> +
>>  endif
>> diff --git a/drivers/cxl/core/Makefile b/drivers/cxl/core/Makefile
>> index 1f66b5d4d935..99e3202f868f 100644
>> --- a/drivers/cxl/core/Makefile
>> +++ b/drivers/cxl/core/Makefile
>> @@ -15,3 +15,4 @@ cxl_core-y += hdm.o
>>  cxl_core-y += pmu.o
>>  cxl_core-$(CONFIG_TRACING) += trace.o
>>  cxl_core-$(CONFIG_CXL_REGION) += region.o
>> +cxl_core-$(CONFIG_CXL_SCRUB) += memscrub.o
>> diff --git a/drivers/cxl/core/memscrub.c b/drivers/cxl/core/memscrub.c
>> new file mode 100644 index 000000000000..ec67ffc81363
>> --- /dev/null
>> +++ b/drivers/cxl/core/memscrub.c
>> @@ -0,0 +1,455 @@
>> +// SPDX-License-Identifier: GPL-2.0-or-later
>> +/*
>> + * cxl_memscrub.c - CXL memory scrub driver
>> + *
>> + * Copyright (c) 2023 HiSilicon Limited.
>> + *
>> + *  - Provides functions to configure patrol scrub
>> + *    feature of the CXL memory devices.
>> + *  - Registers with the scrub driver for the
>> + *    memory patrol scrub feature.
>> + */
>> +
>> +#define pr_fmt(fmt)	"CXL_MEM_SCRUB: " fmt
>> +
>> +#include <cxlmem.h>
>> +#include <memory/memory-scrub.h>
>> +
>> +/* CXL memory scrub feature common definitions */
>> +#define CXL_SCRUB_MAX_ATTRB_RANGE_LENGTH	128
>> +#define CXL_MEMDEV_MAX_NAME_LENGTH	128
>> +
>> +static int cxl_mem_get_supported_feature_entry(struct cxl_memdev *cxlmd,
>const uuid_t *feat_uuid,
>> +					       struct cxl_mbox_supp_feat_entry
>*feat_entry_out) {
>> +	int nentries; /* number of supported feature entries in output payload */
>> +	int feat_index, count;
>> +	bool is_support_feature = false;
>> +	struct cxl_mbox_get_supp_feats_in pi;
>> +	struct cxl_mbox_supp_feat_entry *feat_entry;
>> +	struct cxl_mbox_get_supp_feats_out *feats_out;
>> +	struct cxl_dev_state *cxlds = cxlmd->cxlds;
>> +	struct cxl_memdev_state *mds = to_cxl_memdev_state(cxlds);
>> +
>> +	feat_index = 0;
>> +	do {
>> +		pi.count = sizeof(struct cxl_mbox_get_supp_feats_out) +
>> +				  sizeof(struct cxl_mbox_supp_feat_entry);
>> +		pi.start_index = feat_index;
>> +		nentries = 0;
>
>Is this needed since you init it to feats_out->entries a few lines below
Will remove.

>
>> +		feats_out = cxl_get_supported_features(mds, &pi);
>> +		if (PTR_ERR_OR_ZERO(feats_out))
>> +			return  PTR_ERR_OR_ZERO(feats_out);
>> +		nentries = feats_out->entries;
>> +		if (!nentries) {
>> +			kvfree(feats_out);
>> +			break;
>> +		}
>> +		/* Check CXL memdev supports the feature */
>> +		feat_entry = (void *)feats_out->feat_entries;
>> +		for (count = 0; count < nentries; count++, feat_entry++) {
>> +			if (uuid_equal(&feat_entry->uuid, feat_uuid)) {
>> +				is_support_feature = true;
>> +				memcpy(feat_entry_out, feat_entry,
>sizeof(*feat_entry_out));
>> +				break;
>> +			}
>> +		}
>> +		kvfree(feats_out);
>> +		if (is_support_feature)
>> +			break;
>> +		feat_index += nentries;
>> +	} while (nentries);
>> +
>> +	if (!is_support_feature)
>> +		return -ENOTSUPP;
>> +
>> +	return 0;
>> +}
>> +
>> +/* CXL memory patrol scrub control definitions */
>> +#define CXL_MEMDEV_PS_GET_FEAT_VERSION	0x01
>> +#define CXL_MEMDEV_PS_SET_FEAT_VERSION	0x01
>> +
>> +#define CXL_PATROL_SCRUB	"cxl_patrol_scrub"
>> +
>> +/* The default number of regions for CXL memory device patrol
>> +scrubber
>> + * Patrol scrub is a feature where the device controller scrubs the
>> + * memory at a regular interval accroding to the CXL specification.
>> + * Hence the number of memory regions to scrub assosiated to the
>> +patrol
>> + * scrub is 1.
>> + */
>> +#define CXL_MEMDEV_PATROL_SCRUB_NUM_REGIONS	1
>> +
>> +static const uuid_t cxl_patrol_scrub_uuid =
>> +	UUID_INIT(0x96dad7d6, 0xfde8, 0x482b, 0xa7, 0x33, 0x75, 0x77, 0x4e,
>\
>> +		  0x06, 0xdb, 0x8a);
>> +
>> +/* CXL memory patrol scrub control functions */ struct
>> +cxl_patrol_scrub_context {
>> +	struct device *dev;
>> +	u16 get_feat_size;
>> +	u16 set_feat_size;
>> +	bool scrub_cycle_changable;
>> +};
>> +
>> +/**
>> + * struct cxl_memdev_ps_params - CXL memory patrol scrub parameter data
>structure.
>> + * @enable:     [IN] enable(1)/disable(0) patrol scrub.
>> + * @scrub_cycle_changable: [OUT] scrub cycle attribute of patrol scrub is
>changeable.
>> + * @speed:      [IN] Requested patrol scrub cycle in hours.
>> + *              [OUT] Current patrol scrub cycle in hours.
>> + * @min_speed:[OUT] minimum patrol scrub cycle, in hours, supported.
>> + * @speed_avail:[OUT] Supported patrol scrub cycle in hours.
>> + */
>> +struct cxl_memdev_ps_params {
>> +	bool enable;
>> +	bool scrub_cycle_changable;
>> +	u16 speed;
>> +	u16 min_speed;
>> +	char speed_avail[CXL_SCRUB_MAX_ATTRB_RANGE_LENGTH];
>> +};
>> +
>> +enum {
>> +	CXL_MEMDEV_PS_PARAM_ENABLE = 0,
>> +	CXL_MEMDEV_PS_PARAM_SPEED,
>> +};
>> +
>> +#define	CXL_MEMDEV_PS_SCRUB_CYCLE_CHANGE_CAP_MASK	BIT(0)
>> +#define
>	CXL_MEMDEV_PS_SCRUB_CYCLE_REALTIME_REPORT_CAP_MASK
>	BIT(1)
>> +#define	CXL_MEMDEV_PS_CUR_SCRUB_CYCLE_MASK	GENMASK(7, 0)
>> +#define	CXL_MEMDEV_PS_MIN_SCRUB_CYCLE_MASK	GENMASK(15,
>8)
>> +#define	CXL_MEMDEV_PS_FLAG_ENABLED_MASK	BIT(0)
>> +
>> +struct cxl_memdev_ps_feat_read_attrbs {
>> +	u8 scrub_cycle_cap;
>> +	__le16 scrub_cycle;
>> +	u8 scrub_flags;
>> +}  __packed;
>> +
>> +struct cxl_memdev_ps_set_feat_pi {
>> +	struct cxl_mbox_set_feat_in pi;
>> +	u8 scrub_cycle_hr;
>> +	u8 scrub_flags;
>> +}  __packed;
>> +
>> +static int cxl_mem_ps_get_attrbs(struct device *dev,
>> +				 struct cxl_memdev_ps_params *params) {
>> +	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
>> +	struct cxl_dev_state *cxlds = cxlmd->cxlds;
>> +	struct cxl_memdev_state *mds = to_cxl_memdev_state(cxlds);
>> +	struct cxl_mbox_get_feat_in pi = {
>> +		.uuid = cxl_patrol_scrub_uuid,
>> +		.offset = 0,
>> +		.count = sizeof(struct cxl_memdev_ps_feat_read_attrbs),
>> +		.selection = CXL_GET_FEAT_CURRENT_VALUE,
>> +	};
>> +	struct cxl_memdev_ps_feat_read_attrbs *rd_attrbs;
>> +
>> +	if (!mds)
>> +		return -EFAULT;
>> +
>> +	rd_attrbs = cxl_get_feature(mds, &pi);
>> +	if (PTR_ERR_OR_ZERO(rd_attrbs)) {
>> +		params->enable = 0;
>> +		params->speed = 0;
>> +		snprintf(params->speed_avail,
>CXL_SCRUB_MAX_ATTRB_RANGE_LENGTH,
>> +			"Unavailable");
>> +		return PTR_ERR_OR_ZERO(rd_attrbs);
>> +	}
>> +	params->scrub_cycle_changable =
>FIELD_GET(CXL_MEMDEV_PS_SCRUB_CYCLE_CHANGE_CAP_MASK,
>> +						  rd_attrbs->scrub_cycle_cap);
>> +	params->enable =
>FIELD_GET(CXL_MEMDEV_PS_FLAG_ENABLED_MASK,
>> +				   rd_attrbs->scrub_flags);
>> +	params->speed =
>FIELD_GET(CXL_MEMDEV_PS_CUR_SCRUB_CYCLE_MASK,
>> +				  rd_attrbs->scrub_cycle);
>> +	params->min_speed  =
>FIELD_GET(CXL_MEMDEV_PS_MIN_SCRUB_CYCLE_MASK,
>> +				       rd_attrbs->scrub_cycle);
>> +	snprintf(params->speed_avail,
>CXL_SCRUB_MAX_ATTRB_RANGE_LENGTH,
>> +		 "Minimum scrub cycle = %d hour", params->min_speed);
>> +	kvfree(rd_attrbs);
>> +
>> +	return 0;
>> +}
>> +
>> +static int cxl_mem_ps_set_attrbs(struct device *dev,
>> +				 struct cxl_memdev_ps_params *params, u8
>param_type) {
>> +	int ret;
>> +	struct cxl_memdev_ps_params rd_params;
>> +	struct cxl_memdev_ps_set_feat_pi set_pi = {
>> +		.pi.uuid = cxl_patrol_scrub_uuid,
>> +		.pi.flags =
>CXL_SET_FEAT_FLAG_MOD_VALUE_SAVED_ACROSS_RESET |
>> +
>CXL_SET_FEAT_FLAG_ACTION_FULL_DATA_TRANSFER,
>> +		.pi.offset = 0,
>> +		.pi.version = CXL_MEMDEV_PS_SET_FEAT_VERSION,
>> +	};
>> +	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
>> +	struct cxl_dev_state *cxlds = cxlmd->cxlds;
>> +	struct cxl_memdev_state *mds = to_cxl_memdev_state(cxlds);
>> +
>> +	if (!mds)
>> +		return -EFAULT;
>> +
>> +	ret = 0;
>
>Why set to 0 and then overwrite it in the next line?
Will remove.

>
>> +	ret = cxl_mem_ps_get_attrbs(dev, &rd_params);
>> +	if (ret) {
>> +		dev_err(dev, "Get cxlmemdev patrol scrub params fail
>ret=%d\n",
>> +			ret);
>> +		return ret;
>> +	}
>> +
>> +	if (param_type == CXL_MEMDEV_PS_PARAM_ENABLE) {
>> +		set_pi.scrub_flags =
>FIELD_PREP(CXL_MEMDEV_PS_FLAG_ENABLED_MASK,
>> +						   params->enable);
>> +		set_pi.scrub_cycle_hr =
>FIELD_PREP(CXL_MEMDEV_PS_CUR_SCRUB_CYCLE_MASK,
>> +						      rd_params.speed);
>> +	} else if (param_type == CXL_MEMDEV_PS_PARAM_SPEED) {
>> +		if (params->speed < rd_params.min_speed) {
>> +			dev_err(dev, "Invalid CXL patrol scrub cycle(%d) to
>set\n",
>> +				params->speed);
>> +			dev_err(dev, "Minimum supported CXL patrol scrub
>cycle in hour %d\n",
>> +			       params->min_speed);
>> +			return -EINVAL;
>> +		}
>> +		set_pi.scrub_cycle_hr =
>FIELD_PREP(CXL_MEMDEV_PS_CUR_SCRUB_CYCLE_MASK,
>> +						      params->speed);
>> +		set_pi.scrub_flags =
>FIELD_PREP(CXL_MEMDEV_PS_FLAG_ENABLED_MASK,
>> +						   rd_params.enable);
>> +	} else {
>> +		dev_err(dev, "Invalid CXL patrol scrub parameter to set\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	ret = 0;
>
>unnecessary init?
Ok. Will remove.

>
>> +	ret = cxl_set_feature(mds, &set_pi, sizeof(set_pi));
>> +	if (ret) {
>> +		dev_err(dev, "CXL patrol scrub set feature fail ret=%d\n",
>> +			ret);
>> +		return ret;
>> +	}
>> +
>> +	/* Verify attribute set successfully */
>> +	if (param_type == CXL_MEMDEV_PS_PARAM_SPEED) {
>> +		ret = cxl_mem_ps_get_attrbs(dev, &rd_params);
>> +		if (ret) {
>> +			dev_err(dev, "Get cxlmemdev patrol scrub params fail
>ret=%d\n", ret);
>> +			return ret;
>> +		}
>> +		if (rd_params.speed != params->speed)
>> +			return -EFAULT;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static int cxl_mem_ps_enable_write(struct device *dev, long val) {
>> +	int ret;
>> +	struct cxl_memdev_ps_params params;
>> +
>> +	params.enable = val;
>> +	ret = cxl_mem_ps_set_attrbs(dev, &params,
>CXL_MEMDEV_PS_PARAM_ENABLE);
>> +	if (ret) {
>> +		dev_err(dev, "CXL patrol scrub enable fail, enable=%d
>ret=%d\n",
>> +		       params.enable, ret);
>> +		return ret;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static int cxl_mem_ps_speed_read(struct device *dev, u64 *val) {
>> +	int ret;
>> +	struct cxl_memdev_ps_params params;
>> +
>> +	ret = cxl_mem_ps_get_attrbs(dev, &params);
>> +	if (ret) {
>> +		dev_err(dev, "Get CXL patrol scrub params fail ret=%d\n",
>> +			ret);
>> +		return ret;
>> +	}
>> +	*val = params.speed;
>> +
>> +	return 0;
>> +}
>> +
>> +static int cxl_mem_ps_speed_write(struct device *dev, long val) {
>> +	int ret;
>> +	struct cxl_memdev_ps_params params;
>> +
>> +	params.speed = val;
>> +	ret = cxl_mem_ps_set_attrbs(dev, &params,
>CXL_MEMDEV_PS_PARAM_SPEED);
>> +	if (ret) {
>> +		dev_err(dev, "Set CXL patrol scrub params for speed fail
>ret=%d\n",
>> +			ret);
>> +		return ret;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static int cxl_mem_ps_speed_available_read(struct device *dev, char
>> +*buf) {
>> +	int ret;
>> +	struct cxl_memdev_ps_params params;
>> +
>> +	ret = cxl_mem_ps_get_attrbs(dev, &params);
>> +	if (ret) {
>> +		dev_err(dev, "Get CXL patrol scrub params fail ret=%d\n",
>> +			ret);
>> +		return ret;
>> +	}
>> +
>> +	sprintf(buf, "%s\n", params.speed_avail);
>> +
>> +	return 0;
>> +}
>> +
>> +/**
>> + * cxl_mem_patrol_scrub_is_visible() - Callback to return attribute
>> +visibility
>> + * @drv_data: Pointer to driver-private data structure passed
>> + *	      as argument to devm_scrub_device_register().
>> + * @attr: Scrub attribute
>> + * @region_id: ID of the memory region
>> + *
>> + * Returns: 0 on success, an error otherwise  */ umode_t
>> +cxl_mem_patrol_scrub_is_visible(const void *drv_data, u32 attr, int
>> +region_id) {
>> +	const struct cxl_patrol_scrub_context *cxl_ps_ctx = drv_data;
>> +
>> +	if (attr == scrub_speed_available ||
>> +	    attr == scrub_speed) {
>> +		if (!cxl_ps_ctx->scrub_cycle_changable)
>> +			return 0;
>> +	}
>> +
>> +	switch (attr) {
>> +	case scrub_speed_available:
>> +		return 0444;
>> +	case scrub_enable:
>> +		return 0200;
>> +	case scrub_speed:
>> +		return 0644;
>> +	default:
>> +		return 0;
>> +	}
>> +}
>> +
>> +/**
>> + * cxl_mem_patrol_scrub_read() - Read callback for data attributes
>> + * @dev: Pointer to scrub device
>> + * @attr: Scrub attribute
>> + * @region_id: ID of the memory region
>> + * @val: Pointer to the returned data
>> + *
>> + * Returns: 0 on success, an error otherwise  */ int
>> +cxl_mem_patrol_scrub_read(struct device *dev, u32 attr, int
>> +region_id, u64 *val) {
>> +
>> +	switch (attr) {
>> +	case scrub_speed:
>> +		return cxl_mem_ps_speed_read(dev->parent, val);
>> +	default:
>> +		return -ENOTSUPP;
>> +	}
>> +}
>> +
>> +/**
>> + * cxl_mem_patrol_scrub_write() - Write callback for data attributes
>> + * @dev: Pointer to scrub device
>> + * @attr: Scrub attribute
>> + * @region_id: ID of the memory region
>> + * @val: Value to write
>> + *
>> + * Returns: 0 on success, an error otherwise  */ int
>> +cxl_mem_patrol_scrub_write(struct device *dev, u32 attr, int
>> +region_id, u64 val) {
>> +	switch (attr) {
>> +	case scrub_enable:
>> +		return cxl_mem_ps_enable_write(dev->parent, val);
>> +	case scrub_speed:
>> +		return cxl_mem_ps_speed_write(dev->parent, val);
>> +	default:
>> +		return -ENOTSUPP;
>> +	}
>> +}
>> +
>> +/**
>> + * cxl_mem_patrol_scrub_read_strings() - Read callback for string
>> +attributes
>> + * @dev: Pointer to scrub device
>> + * @attr: Scrub attribute
>> + * @region_id: ID of the memory region
>> + * @buf: Pointer to the buffer for copying returned string
>> + *
>> + * Returns: 0 on success, an error otherwise  */ int
>> +cxl_mem_patrol_scrub_read_strings(struct device *dev, u32 attr, int
>region_id,
>> +				      char *buf)
>> +{
>> +	switch (attr) {
>> +	case scrub_speed_available:
>> +		return cxl_mem_ps_speed_available_read(dev->parent, buf);
>> +	default:
>> +		return -ENOTSUPP;
>> +	}
>> +}
>> +
>> +static const struct scrub_ops cxl_ps_scrub_ops = {
>> +	.is_visible = cxl_mem_patrol_scrub_is_visible,
>> +	.read = cxl_mem_patrol_scrub_read,
>> +	.write = cxl_mem_patrol_scrub_write,
>> +	.read_string = cxl_mem_patrol_scrub_read_strings,
>> +};
>> +
>> +int cxl_mem_patrol_scrub_init(struct cxl_memdev *cxlmd) {
>> +	int ret = 0;
>> +	struct device *cxl_scrub_dev;
>> +	struct cxl_memdev_ps_params params;
>> +	struct cxl_mbox_supp_feat_entry feat_entry;
>> +	char scrub_name[CXL_MEMDEV_MAX_NAME_LENGTH];
>> +	struct cxl_patrol_scrub_context *cxl_ps_ctx;
>> +
>> +	ret = cxl_mem_get_supported_feature_entry(cxlmd,
>&cxl_patrol_scrub_uuid,
>> +						  &feat_entry);
>> +	if (ret < 0)
>> +		goto cxl_ps_init_exit;
>> +
>> +	if (!(feat_entry.attrb_flags & CXL_FEAT_ENTRY_FLAG_CHANGABLE))
>> +		goto cxl_ps_init_exit;
>> +
>> +	cxl_ps_ctx = devm_kzalloc(&cxlmd->dev, sizeof(*cxl_ps_ctx),
>GFP_KERNEL);
>> +	if (!cxl_ps_ctx)
>> +		goto cxl_ps_init_exit;
>> +
>> +	cxl_ps_ctx->get_feat_size = feat_entry.get_feat_size;
>> +	cxl_ps_ctx->set_feat_size = feat_entry.set_feat_size;
>> +	ret = cxl_mem_ps_get_attrbs(&cxlmd->dev, &params);
>> +	if (ret) {
>> +		dev_err(&cxlmd->dev, "Get CXL patrol scrub params fail
>ret=%d\n",
>> +			ret);
>> +		goto cxl_ps_init_exit;
>> +	}
>> +	cxl_ps_ctx->scrub_cycle_changable =  params.scrub_cycle_changable;
>> +
>> +	snprintf(scrub_name, sizeof(scrub_name), "%s_%s",
>> +		 CXL_PATROL_SCRUB, dev_name(&cxlmd->dev));
>> +	cxl_scrub_dev = devm_scrub_device_register(&cxlmd->dev,
>scrub_name,
>> +						   cxl_ps_ctx,
>&cxl_ps_scrub_ops,
>> +
>CXL_MEMDEV_PATROL_SCRUB_NUM_REGIONS);
>> +	if (PTR_ERR_OR_ZERO(cxl_scrub_dev)) {
>> +		ret = PTR_ERR_OR_ZERO(cxl_scrub_dev);
>> +		goto cxl_ps_reg_fail;
>> +	}
>> +
>> +cxl_ps_reg_fail:
>> +cxl_ps_init_exit:
>> +	return ret;
>> +}
>> +EXPORT_SYMBOL_NS_GPL(cxl_mem_patrol_scrub_init, CXL);
>> diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h index
>> fdac686560d4..1d0fad0dc5ae 100644
>> --- a/drivers/cxl/cxlmem.h
>> +++ b/drivers/cxl/cxlmem.h
>> @@ -969,6 +969,13 @@ int cxl_trigger_poison_list(struct cxl_memdev
>> *cxlmd);  int cxl_inject_poison(struct cxl_memdev *cxlmd, u64 dpa);
>> int cxl_clear_poison(struct cxl_memdev *cxlmd, u64 dpa);
>>
>> +/* cxl memory scrub functions */
>> +#ifdef CONFIG_CXL_SCRUB
>> +int cxl_mem_patrol_scrub_init(struct cxl_memdev *cxlmd); #else int
>> +cxl_mem_patrol_scrub_init(struct cxl_memdev *cxlmd) { return
>> +-ENOTSUP; } #endif
>> +
>>  #ifdef CONFIG_CXL_SUSPEND
>>  void cxl_mem_active_inc(void);
>>  void cxl_mem_active_dec(void);
>> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c index
>> 0155fb66b580..86bba8794bb4 100644
>> --- a/drivers/cxl/pci.c
>> +++ b/drivers/cxl/pci.c
>> @@ -881,6 +881,12 @@ static int cxl_pci_probe(struct pci_dev *pdev, const
>struct pci_device_id *id)
>>  	if (rc)
>>  		return rc;
>>
>> +	/*
>> +	 * Initialize optional CXL scrub features
>> +	 */
>> +	if (cxl_mem_patrol_scrub_init(cxlmd))
>> +		dev_dbg(&pdev->dev, "cxl_mem_patrol_scrub_init failed\n");
>> +
>>  	rc = devm_cxl_sanitize_setup_notifier(&pdev->dev, cxlmd);
>>  	if (rc)
>>  		return rc;

Thanks,
Shiju