drm/radeon: clean up atpx power control handling

The presence of the power control method should be determined
via the presence of the method in function 0.  However, some
sbioses only set the appropriate bits in function 1 so use
then to override a missing power control function.
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/radeon_atpx_handler.c

@@ -141,18 +141,12 @@ static void radeon_atpx_parse_functions(struct radeon_atpx_functions *f, u32 mas
  */
 static int radeon_atpx_validate(struct radeon_atpx *atpx)
 {
-	/* make sure required functions are enabled */
-	/* dGPU power control is required */
-	if (atpx->functions.power_cntl == false) {
-		printk("ATPX dGPU power cntl not present, forcing\n");
-		atpx->functions.power_cntl = true;
-	}
+	u32 valid_bits = 0;
 
 	if (atpx->functions.px_params) {
 		union acpi_object *info;
 		struct atpx_px_params output;
 		size_t size;
-		u32 valid_bits;
 
 		info = radeon_atpx_call(atpx->handle, ATPX_FUNCTION_GET_PX_PARAMETERS, NULL);
 		if (!info)
@@ -171,6 +165,10 @@ static int radeon_atpx_validate(struct radeon_atpx *atpx)
 		memcpy(&output, info->buffer.pointer, size);
 
 		valid_bits = output.flags & output.valid_flags;
+
+		kfree(info);
+	}
+
 	/* if separate mux flag is set, mux controls are required */
 	if (valid_bits & ATPX_SEPARATE_MUX_FOR_I2C) {
 		atpx->functions.i2c_mux_cntl = true;
@@ -182,13 +180,21 @@ static int radeon_atpx_validate(struct radeon_atpx *atpx)
 			  ATPX_DFP_SIGNAL_MUXED))
 		atpx->functions.disp_mux_cntl = true;
 
+	/* some bioses set these bits rather than flagging power_cntl as supported */
+	if (valid_bits & (ATPX_DYNAMIC_PX_SUPPORTED |
+			  ATPX_DYNAMIC_DGPU_POWER_OFF_SUPPORTED))
+		atpx->functions.power_cntl = true;
+
 	if (valid_bits & ATPX_MS_HYBRID_GFX_SUPPORTED) {
 		printk("Hybrid Graphics, ATPX dGPU power cntl disabled\n");
 		atpx->functions.power_cntl = false;
+	} else if (atpx->functions.power_cntl == false) {
+		/* make sure required functions are enabled */
+		/* dGPU power control is required */
+		printk("ATPX dGPU power cntl not present, forcing\n");
+		atpx->functions.power_cntl = true;
 	}
 
-		kfree(info);
-	}
 	return 0;
 }