linux-kernel - [PATCH 5.4 29/32] drm/amd/display: Change function decide_dp_link

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Date:   Fri,  5 Feb 2021 15:07:44 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Daniel Wheeler <daniel.wheeler@....com>,
        Bing Guo <bing.guo@....com>, Jun Lei <Jun.Lei@....com>,
        Anson Jacob <anson.jacob@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 29/32] drm/amd/display: Change function decide_dp_link_settings to avoid infinite looping

From: Bing Guo <bing.guo@....com>

[ Upstream commit 4716a7c50c5c66d6ddc42401e1e0ba13b492e105 ]

Why:
Function decide_dp_link_settings() loops infinitely when required bandwidth
can't be supported.

How:
Check the required bandwidth against verified_link_cap before trying to
find a link setting for it.

Tested-by: Daniel Wheeler <daniel.wheeler@....com>
Signed-off-by: Bing Guo <bing.guo@....com>
Reviewed-by: Jun Lei <Jun.Lei@....com>
Acked-by: Anson Jacob <anson.jacob@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
index 959eb075d11ed..c18f39271b034 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
@@ -1914,6 +1914,9 @@ static bool decide_dp_link_settings(struct dc_link *link, struct dc_link_setting
 			initial_link_setting;
 	uint32_t link_bw;
 
+	if (req_bw > dc_link_bandwidth_kbps(link, &link->verified_link_cap))
+		return false;
+
 	/* search for the minimum link setting that:
 	 * 1. is supported according to the link training result
 	 * 2. could support the b/w requested by the timing
-- 
2.27.0