drm/amdgpu: expose amdgpu_sensors on pre-powerplay chips

read_sensor() has been recently implemented for dpm based boards
which means amdgpu_sensors can now be exposed.

v2: - make sure read_sensor is not NULL on dpm chips
    - keep sanity check for powerplay chips
v3: - make sure amdgpu_dpm != 0

Cc: Tom St Denis <tom.stdenis@amd.com>
Reviewed-by: Tom St Denis <tom.stdenis@amd.com>
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_device.c

@@ -3112,12 +3112,18 @@ static ssize_t amdgpu_debugfs_sensor_read(struct file *f, char __user *buf,
 	if (size & 3 || *pos & 0x3)
 		return -EINVAL;
 
+	if (amdgpu_dpm == 0)
+		return -EINVAL;
+
 	/* convert offset to sensor number */
 	idx = *pos >> 2;
 
 	valuesize = sizeof(values);
 	if (adev->powerplay.pp_funcs && adev->powerplay.pp_funcs->read_sensor)
 		r = adev->powerplay.pp_funcs->read_sensor(adev->powerplay.pp_handle, idx, &values[0], &valuesize);
+	else if (adev->pm.funcs && adev->pm.funcs->read_sensor)
+		r = adev->pm.funcs->read_sensor(adev, idx, &values[0],
+						&valuesize);
 	else
 		return -EINVAL;