[PATCH v8] ufs: core: print UFSHCD capabilities in controller's sysfs node

[PATCH v8] ufs: core: print UFSHCD capabilities in controller's sysfs node

[Daniil Lunev]

Userspace may want to manually control when the data should go into
WriteBooster buffer. The control happens via "wb_on" node, but
presently, there is no simple way to check if WriteBooster is supported
and enabled. This change exposes the Write Booster and Clock Scaling
capabilities to be able to determin if the Write Booster is available
and if its manual control is blocked by Clock Scaling mechanism.

Signed-off-by: Daniil Lunev <dlunev@chromium.org>

---

Changes in v8:
* Expand commit message with motiviation.

Changes in v7:
* Move the comment to the documnetation
* Update the month on the documentation

Changes in v6:
* Add comment to clarify meaning of the "capbilities" sysfs group.

Changes in v5:
* Correct wording for clock scaling.
* Correct wording for the commit message.

Changes in v4:
* Dropped crypto node per Eric Biggers mentioning it can be queried from
  disk's queue node

Changes in v3:
* Expose each capability individually.
* Update documentation to represent new scheme.

Changes in v2:
* Add documentation entry for the new sysfs node.

 Documentation/ABI/testing/sysfs-driver-ufs | 37 ++++++++++++++++++++++
 drivers/ufs/core/ufs-sysfs.c               | 35 ++++++++++++++++++++
 2 files changed, 72 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-driver-ufs b/Documentation/ABI/testing/sysfs-driver-ufs
index 6b248abb1bd71..78f3e393d2498 100644
--- a/Documentation/ABI/testing/sysfs-driver-ufs
+++ b/Documentation/ABI/testing/sysfs-driver-ufs
@@ -1591,6 +1591,43 @@ Description:	This entry shows the status of HPB.
 
 		The file is read only.
 
+Contact:	Daniil Lunev <dlunev@chromium.org>
+What:		/sys/bus/platform/drivers/ufshcd/*/capabilities/
+What:		/sys/bus/platform/devices/*.ufs/capabilities/
+Date:		August 2022
+Description:	The group represents the effective capabilities of the
+		host-device pair. i.e. the capabilities which are enabled in the
+		driver for the specific host controller, supported by the host
+		controller and are supported and/or have compatible
+		configuration on the device side.
+
+Contact:	Daniil Lunev <dlunev@chromium.org>
+What:		/sys/bus/platform/drivers/ufshcd/*/capabilities/clock_scaling
+What:		/sys/bus/platform/devices/*.ufs/capabilities/clock_scaling
+Date:		August 2022
+Contact:	Daniil Lunev <dlunev@chromium.org>
+Description:	Indicates status of clock scaling.
+
+		== ============================
+		0  Clock scaling is not supported.
+		1  Clock scaling is supported.
+		== ============================
+
+		The file is read only.
+
+What:		/sys/bus/platform/drivers/ufshcd/*/capabilities/write_booster
+What:		/sys/bus/platform/devices/*.ufs/capabilities/write_booster
+Date:		August 2022
+Contact:	Daniil Lunev <dlunev@chromium.org>
+Description:	Indicates status of Write Booster.
+
+		== ============================
+		0  Write Booster can not be enabled.
+		1  Write Booster can be enabled.
+		== ============================
+
+		The file is read only.
+
 What:		/sys/class/scsi_device/*/device/hpb_param_sysfs/activation_thld
 Date:		February 2021
 Contact:	Avri Altman <avri.altman@wdc.com>
diff --git a/drivers/ufs/core/ufs-sysfs.c b/drivers/ufs/core/ufs-sysfs.c
index 0a088b47d5570..75d4287657c80 100644
--- a/drivers/ufs/core/ufs-sysfs.c
+++ b/drivers/ufs/core/ufs-sysfs.c
@@ -279,6 +279,40 @@ static const struct attribute_group ufs_sysfs_default_group = {
 	.attrs = ufs_sysfs_ufshcd_attrs,
 };
 
+static ssize_t clock_scaling_show(struct device *dev, struct device_attribute *attr,
+				  char *buf)
+{
+	struct ufs_hba *hba = dev_get_drvdata(dev);
+
+	return sysfs_emit(buf, "%d\n", ufshcd_is_clkscaling_supported(hba));
+}
+
+static ssize_t write_booster_show(struct device *dev, struct device_attribute *attr,
+				  char *buf)
+{
+	struct ufs_hba *hba = dev_get_drvdata(dev);
+
+	return sysfs_emit(buf, "%d\n", ufshcd_is_wb_allowed(hba));
+}
+
+static DEVICE_ATTR_RO(clock_scaling);
+static DEVICE_ATTR_RO(write_booster);
+
+/*
+ * See Documentation/ABI/testing/sysfs-driver-ufs for the semantics of this
+ * group.
+ */
+static struct attribute *ufs_sysfs_capabilities_attrs[] = {
+	&dev_attr_clock_scaling.attr,
+	&dev_attr_write_booster.attr,
+	NULL
+};
+
+static const struct attribute_group ufs_sysfs_capabilities_group = {
+	.name = "capabilities",
+	.attrs = ufs_sysfs_capabilities_attrs,
+};
+
 static ssize_t monitor_enable_show(struct device *dev,
 				   struct device_attribute *attr, char *buf)
 {
@@ -1134,6 +1168,7 @@ static const struct attribute_group ufs_sysfs_attributes_group = {
 
 static const struct attribute_group *ufs_sysfs_groups[] = {
 	&ufs_sysfs_default_group,
+	&ufs_sysfs_capabilities_group,
 	&ufs_sysfs_monitor_group,
 	&ufs_sysfs_device_descriptor_group,
 	&ufs_sysfs_interconnect_descriptor_group,
-- 
2.31.0

Re: [PATCH v8] ufs: core: print UFSHCD capabilities in controller's sysfs node

[Bart Van Assche]

On 8/28/22 15:18, Daniil Lunev wrote:
> Userspace may want to manually control when the data should go into
> WriteBooster buffer. The control happens via "wb_on" node, but
> presently, there is no simple way to check if WriteBooster is supported
> and enabled. This change exposes the Write Booster and Clock Scaling
> capabilities to be able to determin if the Write Booster is available
> and if its manual control is blocked by Clock Scaling mechanism.

determin -> determine?

Anyway:

Reviewed-by: Bart Van Assche <bvanassche@acm.org>

Re: [PATCH v8] ufs: core: print UFSHCD capabilities in controller's sysfs node

[Martin K. Petersen]

Daniil,

> Userspace may want to manually control when the data should go into
> WriteBooster buffer. The control happens via "wb_on" node, but
> presently, there is no simple way to check if WriteBooster is
> supported and enabled. This change exposes the Write Booster and Clock
> Scaling capabilities to be able to determin if the Write Booster is
> available and if its manual control is blocked by Clock Scaling
> mechanism.

Applied to 6.1/scsi-staging, thanks!

-- 
Martin K. Petersen	Oracle Linux Engineering