amdgpu/pm: add kernel documentation for smu_get_power_limit

 added doc tag "amdgpu_pp_power" with description
 added tags for enums  pp_power_limit_level, pp_power_type
 added tag for function smu_get_power_limit

Test:
* Temporary insertion into Documentation/gpu/amdgpu.rst
------------START------------
Power Limit
-----------
.. kernel-doc:: drivers/gpu/drm/amd/include/kgd_pp_interface.h
   :doc: amdgpu_pp_power

.. kernel-doc:: drivers/gpu/drm/amd/include/kgd_pp_interface.h
   :identifiers: pp_power_limit_level

.. kernel-doc:: drivers/gpu/drm/amd/include/kgd_pp_interface.h
   :identifiers: pp_power_type

.. kernel-doc:: drivers/gpu/drm/amd/pm/swsmu/amdgpu_smu.c
   :identifiers: smu_get_power_limit
-------------END-------------
Signed-off-by: Darren Powell <darren.powell@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/include/kgd_pp_interface.h

@@ -194,6 +194,26 @@ enum pp_df_cstate {
 	DF_CSTATE_ALLOW,
 };
 
+/**
+ * DOC: amdgpu_pp_power
+ *
+ * APU power is managed to system-level requirements through the PPT
+ * (package power tracking) feature. PPT is intended to limit power to the
+ * requirements of the power source and could be dynamically updated to
+ * maximize APU performance within the system power budget.
+ *
+ * Two types of power measurement can be requested, where supported, with
+ * :c:type:`enum pp_power_type <pp_power_type>`.
+ */
+
+/**
+ * enum pp_power_limit_level - Used to query the power limits
+ *
+ * @PP_PWR_LIMIT_MIN: Minimum Power Limit
+ * @PP_PWR_LIMIT_CURRENT: Current Power Limit
+ * @PP_PWR_LIMIT_DEFAULT: Default Power Limit
+ * @PP_PWR_LIMIT_MAX: Maximum Power Limit
+ */
 enum pp_power_limit_level
 {
 	PP_PWR_LIMIT_MIN = -1,
@@ -202,6 +222,14 @@ enum pp_power_limit_level
 	PP_PWR_LIMIT_MAX,
 };
 
+/**
+ * enum pp_power_type - Used to specify the type of the requested power
+ *
+ * @PP_PWR_TYPE_SUSTAINED: manages the configurable, thermally significant
+ * moving average of APU power (default ~5000 ms).
+ * @PP_PWR_TYPE_FAST: manages the ~10 ms moving average of APU power,
+ * where supported.
+ */
 enum pp_power_type
 {
 	PP_PWR_TYPE_SUSTAINED,

drivers/gpu/drm/amd/pm/swsmu/amdgpu_smu.c

@@ -2173,6 +2173,16 @@ static int smu_set_fan_speed_rpm(void *handle, uint32_t speed)
 	return ret;
 }
 
+/**
+ * smu_get_power_limit - Request one of the SMU Power Limits
+ *
+ * @handle: pointer to smu context
+ * @limit: requested limit is written back to this variable
+ * @pp_limit_level: &pp_power_limit_level which limit of the power to return
+ * @pp_power_type: &pp_power_type type of power
+ * Return:  0 on success, <0 on error
+ *
+ */
 int smu_get_power_limit(void *handle,
 			uint32_t *limit,
 			enum pp_power_limit_level pp_limit_level,