From: Wang Fudong <Fudong.Wang@xxxxxxx> [Why] DIG_FIFO_ERROR = 1 caused mst daisy chain 2nd monitor black. [How] We need to set dig fifo read start level = 7 before dig fifo reset during dig fifo enable according to hardware designer's suggestion. If it is zero, it will cause underflow or overflow and DIG_FIFO_ERROR = 1. Reviewed-by: Alvin Lee <Alvin.Lee2@xxxxxxx> Reviewed-by: Aric Cyr <Aric.Cyr@xxxxxxx> Acked-by: Brian Chang <Brian.Chang@xxxxxxx> Signed-off-by: Wang Fudong <Fudong.Wang@xxxxxxx> --- .../gpu/drm/amd/display/dc/dcn32/dcn32_dio_stream_encoder.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/gpu/drm/amd/display/dc/dcn32/dcn32_dio_stream_encoder.c b/drivers/gpu/drm/amd/display/dc/dcn32/dcn32_dio_stream_encoder.c index 26648ce772da..38a48983f663 100644 --- a/drivers/gpu/drm/amd/display/dc/dcn32/dcn32_dio_stream_encoder.c +++ b/drivers/gpu/drm/amd/display/dc/dcn32/dcn32_dio_stream_encoder.c @@ -310,6 +310,11 @@ static void enc32_stream_encoder_dp_unblank( // TODO: Confirm if we need to wait for DIG_SYMCLK_FE_ON REG_WAIT(DIG_FE_CNTL, DIG_SYMCLK_FE_ON, 1, 10, 5000); + /* read start level = 0 will bring underflow / overflow and DIG_FIFO_ERROR = 1 + * so set it to 1/2 full = 7 before reset as suggested by hardware team. + */ + REG_UPDATE(DIG_FIFO_CTRL0, DIG_FIFO_READ_START_LEVEL, 0x7); + REG_UPDATE(DIG_FIFO_CTRL0, DIG_FIFO_RESET, 1); REG_WAIT(DIG_FIFO_CTRL0, DIG_FIFO_RESET_DONE, 1, 10, 5000); -- 2.25.1
