linux-kernel - [PATCH AUTOSEL 5.10 20/20] drm/amd/display: workaround for hard hang on HPD on native DP

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Message-Id: <20210810141538.3117707-20-sashal@kernel.org>
Date:   Tue, 10 Aug 2021 10:15:38 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Qingqing Zhuo <qingqing.zhuo@....com>,
        Hersen Wu <hersenxs.wu@....com>,
        Aurabindo Pillai <aurabindo.pillai@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 5.10 20/20] drm/amd/display: workaround for hard hang on HPD on native DP

From: Qingqing Zhuo <qingqing.zhuo@....com>

[ Upstream commit c4152b297d56d3696ad0a9003169bc5b98ad7b72 ]

[Why]
HPD disable and enable sequences are not mutually exclusive
on Linux. For HPDs that spans over 1s (i.e. HPD low = 1s),
part of the disable sequence (specifically, a request to SMU
to lower refclk) could come right before the call to PHY
enable, causing DMUB to access an unresponsive PHY
and thus a hard hang on the system.

[How]
Disable 48mhz refclk off on native DP.

Reviewed-by: Hersen Wu <hersenxs.wu@....com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@....com>
Signed-off-by: Qingqing Zhuo <qingqing.zhuo@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/amd/display/dc/clk_mgr/dcn21/rn_clk_mgr.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn21/rn_clk_mgr.c b/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn21/rn_clk_mgr.c
index 1c6e401dd4cc..0eba391e597f 100644
--- a/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn21/rn_clk_mgr.c
+++ b/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn21/rn_clk_mgr.c
@@ -66,9 +66,11 @@ int rn_get_active_display_cnt_wa(
 	for (i = 0; i < context->stream_count; i++) {
 		const struct dc_stream_state *stream = context->streams[i];
 
+		/* Extend the WA to DP for Linux*/
 		if (stream->signal == SIGNAL_TYPE_HDMI_TYPE_A ||
 				stream->signal == SIGNAL_TYPE_DVI_SINGLE_LINK ||
-				stream->signal == SIGNAL_TYPE_DVI_DUAL_LINK)
+				stream->signal == SIGNAL_TYPE_DVI_DUAL_LINK ||
+				stream->signal == SIGNAL_TYPE_DISPLAY_PORT)
 			tmds_present = true;
 	}
 
-- 
2.30.2