drm/amd/pm: Add sysfs attribute to get pm metrics

Add sysfs attribute to read power management metrics. A snapshot is
captured to the buffer when the attribute is read.
Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Yang Wang <kevinyang.wang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/pm/amdgpu_pm.c

@@ -1799,6 +1799,44 @@ static ssize_t amdgpu_set_apu_thermal_cap(struct device *dev,
 	return count;
 }
 
+static int amdgpu_pm_metrics_attr_update(struct amdgpu_device *adev,
+					 struct amdgpu_device_attr *attr,
+					 uint32_t mask,
+					 enum amdgpu_device_attr_states *states)
+{
+	if (amdgpu_dpm_get_pm_metrics(adev, NULL, 0) == -EOPNOTSUPP)
+		*states = ATTR_STATE_UNSUPPORTED;
+
+	return 0;
+}
+
+static ssize_t amdgpu_get_pm_metrics(struct device *dev,
+				     struct device_attribute *attr, char *buf)
+{
+	struct drm_device *ddev = dev_get_drvdata(dev);
+	struct amdgpu_device *adev = drm_to_adev(ddev);
+	ssize_t size = 0;
+	int ret;
+
+	if (amdgpu_in_reset(adev))
+		return -EPERM;
+	if (adev->in_suspend && !adev->in_runpm)
+		return -EPERM;
+
+	ret = pm_runtime_get_sync(ddev->dev);
+	if (ret < 0) {
+		pm_runtime_put_autosuspend(ddev->dev);
+		return ret;
+	}
+
+	size = amdgpu_dpm_get_pm_metrics(adev, buf, PAGE_SIZE);
+
+	pm_runtime_mark_last_busy(ddev->dev);
+	pm_runtime_put_autosuspend(ddev->dev);
+
+	return size;
+}
+
 /**
  * DOC: gpu_metrics
  *
@@ -2096,6 +2134,8 @@ static struct amdgpu_device_attr amdgpu_device_attrs[] = {
 	AMDGPU_DEVICE_ATTR_RW(smartshift_bias,				ATTR_FLAG_BASIC,
 			      .attr_update = ss_bias_attr_update),
 	AMDGPU_DEVICE_ATTR_RW(xgmi_plpd_policy,				ATTR_FLAG_BASIC),
+	AMDGPU_DEVICE_ATTR_RO(pm_metrics,				ATTR_FLAG_BASIC,
+			      .attr_update = amdgpu_pm_metrics_attr_update),
 };
 
 static int default_attr_update(struct amdgpu_device *adev, struct amdgpu_device_attr *attr,