[PATCH v4 10/10] Documentation/amdgpu: Add PM policy documentation

[Lijo Lazar]

Add documentation about the newly added pm_policy node in sysfs.

Signed-off-by: Lijo Lazar <lijo.lazar at amd.com>
---
 Documentation/gpu/amdgpu/thermal.rst |  6 ++++
 drivers/gpu/drm/amd/pm/amdgpu_pm.c   | 48 ++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)

diff --git a/Documentation/gpu/amdgpu/thermal.rst b/Documentation/gpu/amdgpu/thermal.rst
index 2f6166f81e6a..6d942b5c58f0 100644
--- a/Documentation/gpu/amdgpu/thermal.rst
+++ b/Documentation/gpu/amdgpu/thermal.rst
@@ -49,6 +49,12 @@ pp_power_profile_mode
 .. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c
    :doc: pp_power_profile_mode
 
+pm_policy
+---------------------
+
+.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c
+   :doc: pm_policy
+
 \*_busy_percent
 ---------------
 
diff --git a/drivers/gpu/drm/amd/pm/amdgpu_pm.c b/drivers/gpu/drm/amd/pm/amdgpu_pm.c
index 5c92c041d0bc..be39276181a1 100644
--- a/drivers/gpu/drm/amd/pm/amdgpu_pm.c
+++ b/drivers/gpu/drm/amd/pm/amdgpu_pm.c
@@ -2214,6 +2214,54 @@ static int pp_dpm_clk_default_attr_update(struct amdgpu_device *adev, struct amd
 	return 0;
 }
 
+/**
+ * DOC: pm_policy
+ *
+ * Certain SOCs can support different power policies to optimize application
+ * performance. However, this policy is provided only at SOC level and not at a
+ * per-process level. This is useful especially when entire SOC is utilized for
+ * dedicated workload.
+ *
+ * The amdgpu driver provides a sysfs API for selecting the policy. Presently,
+ * only two types of policies are supported through this interface.
+ *
+ *  Pstate Policy Selection - This is to select different Pstate profiles which
+ *  decides clock/throttling preferences.
+ *
+ *  XGMI PLPD Policy Selection - When multiple devices are connected over XGMI,
+ *  this helps to select policy to be applied for per link power down.
+ *
+ * The list of available policies and policy levels vary between SOCs. They can
+ * be viewed by reading the file. The policy level which is applied presently is
+ * denoted by * (asterisk). E.g.,
+ *
+ * .. code-block:: console
+ *
+ *	cat /sys/bus/pci/devices/.../pm_policy
+ *	soc_pstate
+ *	0 : soc_pstate_default
+ *	1 : soc_pstate_0
+ *	2 : soc_pstate_1*
+ *	3 : soc_pstate_2
+ *	xgmi_plpd
+ *	0 : plpd_disallow
+ *	1 : plpd_default
+ *	2 : plpd_optimized*
+ *
+ * To apply a specific policy
+ *
+ * "echo <policy type> <level> > /sys/bus/pci/devices/.../pm_policy"
+ *
+ * For the levels listed in the example above, to select "plpd_optimized" for
+ * XGMI and "soc_pstate_2" for soc pstate policy -
+ *
+ * .. code-block:: console
+ *
+ *	echo "xgmi_plpd 2" > /sys/bus/pci/devices/.../pm_policy
+ *	echo "soc_pstate 3" > /sys/bus/pci/devices/.../pm_policy
+ *
+ */
+
 static ssize_t amdgpu_get_pm_policy(struct device *dev,
 				    struct device_attribute *attr, char *buf)
 {
-- 
2.25.1