[PATCH RFC v2 07/18] cxl/mem: Expose device dynamic capacity configuration

From: ira . weiny
Date: Tue Aug 29 2023 - 01:33:55 EST


From: Navneet Singh <navneet.singh@xxxxxxxxx>

To properly configure CXL regions on Dynamic Capacity Devices (DCD),
user space will need to know the details of the DC Regions available on
a device.

Expose driver dynamic capacity configuration through sysfs
attributes.

Co-developed-by: Navneet Singh <navneet.singh@xxxxxxxxx>
Signed-off-by: Navneet Singh <navneet.singh@xxxxxxxxx>
Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>

---
Changes for v2:
[iweiny: Rebased on latest master/type2 work]
[iweiny: add documentation for sysfs entries]
[iweiny: s/dc_regions_count/region_count/]
[iweiny: s/dcY_size/regionY_size/]
[alison: change size format to %#llx]
[iweiny: change count format to %d]
[iweiny: Formatting updates]
[iweiny: Fix crash when device is not a mem device: found with cxl-test]
---
Documentation/ABI/testing/sysfs-bus-cxl | 17 ++++++++
drivers/cxl/core/memdev.c | 77 +++++++++++++++++++++++++++++++++
2 files changed, 94 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl
index 2268ffcdb604..aa65dc5b4e13 100644
--- a/Documentation/ABI/testing/sysfs-bus-cxl
+++ b/Documentation/ABI/testing/sysfs-bus-cxl
@@ -37,6 +37,23 @@ Description:
identically named field in the Identify Memory Device Output
Payload in the CXL-2.0 specification.

+What: /sys/bus/cxl/devices/memX/dc/region_count
+Date: July, 2023
+KernelVersion: v6.6
+Contact: linux-cxl@xxxxxxxxxxxxxxx
+Description:
+ (RO) Number of Dynamic Capacity (DC) regions supported on the
+ device. May be 0 if the device does not support Dynamic
+ Capacity.
+
+What: /sys/bus/cxl/devices/memX/dc/regionY_size
+Date: July, 2023
+KernelVersion: v6.6
+Contact: linux-cxl@xxxxxxxxxxxxxxx
+Description:
+ (RO) Size of the Dynamic Capacity (DC) region Y. Only
+ available on devices which support DC and only for those
+ region indexes supported by the device.

What: /sys/bus/cxl/devices/memX/serial
Date: January, 2022
diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
index 492486707fd0..397262e0ebd2 100644
--- a/drivers/cxl/core/memdev.c
+++ b/drivers/cxl/core/memdev.c
@@ -101,6 +101,20 @@ static ssize_t pmem_size_show(struct device *dev, struct device_attribute *attr,
static struct device_attribute dev_attr_pmem_size =
__ATTR(size, 0444, pmem_size_show, NULL);

+static ssize_t region_count_show(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
+ struct cxl_memdev_state *mds = to_cxl_memdev_state(cxlmd->cxlds);
+ int len = 0;
+
+ len = sysfs_emit(buf, "%d\n", mds->nr_dc_region);
+ return len;
+}
+
+struct device_attribute dev_attr_region_count =
+ __ATTR(region_count, 0444, region_count_show, NULL);
+
static ssize_t serial_show(struct device *dev, struct device_attribute *attr,
char *buf)
{
@@ -454,6 +468,62 @@ static struct attribute *cxl_memdev_security_attributes[] = {
NULL,
};

+static ssize_t show_size_regionN(struct cxl_memdev *cxlmd, char *buf, int pos)
+{
+ struct cxl_memdev_state *mds = to_cxl_memdev_state(cxlmd->cxlds);
+
+ return sysfs_emit(buf, "%#llx\n", mds->dc_region[pos].decode_len);
+}
+
+#define REGION_SIZE_ATTR_RO(n) \
+static ssize_t region##n##_size_show(struct device *dev, \
+ struct device_attribute *attr, \
+ char *buf) \
+{ \
+ return show_size_regionN(to_cxl_memdev(dev), buf, (n)); \
+} \
+static DEVICE_ATTR_RO(region##n##_size)
+REGION_SIZE_ATTR_RO(0);
+REGION_SIZE_ATTR_RO(1);
+REGION_SIZE_ATTR_RO(2);
+REGION_SIZE_ATTR_RO(3);
+REGION_SIZE_ATTR_RO(4);
+REGION_SIZE_ATTR_RO(5);
+REGION_SIZE_ATTR_RO(6);
+REGION_SIZE_ATTR_RO(7);
+
+static struct attribute *cxl_memdev_dc_attributes[] = {
+ &dev_attr_region0_size.attr,
+ &dev_attr_region1_size.attr,
+ &dev_attr_region2_size.attr,
+ &dev_attr_region3_size.attr,
+ &dev_attr_region4_size.attr,
+ &dev_attr_region5_size.attr,
+ &dev_attr_region6_size.attr,
+ &dev_attr_region7_size.attr,
+ &dev_attr_region_count.attr,
+ NULL,
+};
+
+static umode_t cxl_dc_visible(struct kobject *kobj, struct attribute *a, int n)
+{
+ struct device *dev = kobj_to_dev(kobj);
+ struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
+ struct cxl_memdev_state *mds = to_cxl_memdev_state(cxlmd->cxlds);
+
+ /* Not a memory device */
+ if (!mds)
+ return 0;
+
+ if (a == &dev_attr_region_count.attr)
+ return a->mode;
+
+ if (n < mds->nr_dc_region)
+ return a->mode;
+
+ return 0;
+}
+
static umode_t cxl_memdev_visible(struct kobject *kobj, struct attribute *a,
int n)
{
@@ -482,11 +552,18 @@ static struct attribute_group cxl_memdev_security_attribute_group = {
.attrs = cxl_memdev_security_attributes,
};

+static struct attribute_group cxl_memdev_dc_attribute_group = {
+ .name = "dc",
+ .attrs = cxl_memdev_dc_attributes,
+ .is_visible = cxl_dc_visible,
+};
+
static const struct attribute_group *cxl_memdev_attribute_groups[] = {
&cxl_memdev_attribute_group,
&cxl_memdev_ram_attribute_group,
&cxl_memdev_pmem_attribute_group,
&cxl_memdev_security_attribute_group,
+ &cxl_memdev_dc_attribute_group,
NULL,
};


--
2.41.0