[PATCH 6.19 221/844] drm/amd/display: avoid dig reg access timeout on usb4 link training fail

[Sasha Levin]

From: Zhongwei <Zhongwei.Zhang@xxxxxxx>

[ Upstream commit 15b1d7b77e9836ff4184093163174a1ef28bbdd7 ]

[Why]
When usb4 link training fails, the dpia sym clock will be disabled and SYMCLK
source should be changed back to phy clock. In enable_streams, it is
assumed that link training succeeded and will switch from refclk to
phy clock. But phy clk here might not be on. Dig reg access timeout
will occur.

[How]
When enable_stream is hit, check if link training failed for usb4.
If it did, fall back to the ref clock to avoid reg access timeout.

Reviewed-by: Wenjing Liu <wenjing.liu@xxxxxxx>
Signed-off-by: Zhongwei <Zhongwei.Zhang@xxxxxxx>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@xxxxxxx>
Tested-by: Dan Wheeler <daniel.wheeler@xxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 .../gpu/drm/amd/display/dc/hwss/dcn20/dcn20_hwseq.c  | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/hwss/dcn20/dcn20_hwseq.c b/drivers/gpu/drm/amd/display/dc/hwss/dcn20/dcn20_hwseq.c
index c8ff8ae85a030..517d4c08d34c4 100644
--- a/drivers/gpu/drm/amd/display/dc/hwss/dcn20/dcn20_hwseq.c
+++ b/drivers/gpu/drm/amd/display/dc/hwss/dcn20/dcn20_hwseq.c
@@ -3058,9 +3058,17 @@ void dcn20_enable_stream(struct pipe_ctx *pipe_ctx)
 			dccg->funcs->enable_symclk32_se(dccg, dp_hpo_inst, phyd32clk);
 		}
 	} else {
-		if (dccg->funcs->enable_symclk_se)
-			dccg->funcs->enable_symclk_se(dccg, stream_enc->stream_enc_inst,
+		if (dccg->funcs->enable_symclk_se && link_enc) {
+			if (link->ep_type == DISPLAY_ENDPOINT_USB4_DPIA
+				&& link->cur_link_settings.link_rate == LINK_RATE_UNKNOWN
+				&& !link->link_status.link_active) {
+				if (dccg->funcs->disable_symclk_se)
+					dccg->funcs->disable_symclk_se(dccg, stream_enc->stream_enc_inst,
 						      link_enc->transmitter - TRANSMITTER_UNIPHY_A);
+			} else
+				dccg->funcs->enable_symclk_se(dccg, stream_enc->stream_enc_inst,
+						      link_enc->transmitter - TRANSMITTER_UNIPHY_A);
+		}
 	}
 
 	if (dc->res_pool->dccg->funcs->set_pixel_rate_div)
-- 
2.51.0