drm/amd/display: Don't apply FIFO resync W/A if rdivider = 0

[Description]
It is not valid to set the WDIVIDER value to 0, so do not
re-write to DISPCLK_WDIVIDER if the current value is 0
(i.e., it is at it's initial value and we have not made any
requests to change DISPCLK yet).

Reviewed-by: Saaem Rizvi <syedsaaem.rizvi@amd.com>
Acked-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alvin Lee <alvin.lee2@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Author: Alvin Lee

drivers/gpu/drm/amd/display/dc/dcn32/dcn32_dccg.c

@@ -49,7 +49,10 @@ static void dccg32_trigger_dio_fifo_resync(
 	uint32_t dispclk_rdivider_value = 0;
 
 	REG_GET(DENTIST_DISPCLK_CNTL, DENTIST_DISPCLK_RDIVIDER, &dispclk_rdivider_value);
-	REG_UPDATE(DENTIST_DISPCLK_CNTL, DENTIST_DISPCLK_WDIVIDER, dispclk_rdivider_value);
+
+	/* Not valid for the WDIVIDER to be set to 0 */
+	if (dispclk_rdivider_value != 0)
+		REG_UPDATE(DENTIST_DISPCLK_CNTL, DENTIST_DISPCLK_WDIVIDER, dispclk_rdivider_value);
 }
 
 static void dccg32_get_pixel_rate_div(