linux-kernel - [PATCH 6/9] drm/msm/dp: Work around bogus maximum link rate

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250714173554.14223-7-daleyo@gmail.com>
Date: Mon, 14 Jul 2025 18:35:42 +0100
From: Dale Whinham <daleyo@...il.com>
To: Rob Clark <robdclark@...il.com>,
	Abhinav Kumar <quic_abhinavk@...cinc.com>,
	Dmitry Baryshkov <lumag@...nel.org>,
	Sean Paul <sean@...rly.run>,
	Marijn Suijten <marijn.suijten@...ainline.org>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>
Cc: Jérôme de Bretagne <jerome.debretagne@...il.com>,
	Dale Whinham <daleyo@...il.com>,
	linux-arm-msm@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	freedreno@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 6/9] drm/msm/dp: Work around bogus maximum link rate

From: Jérôme de Bretagne <jerome.debretagne@...il.com>

The OLED display in the Surface Pro 11 reports a maximum link rate of
zero in its DPCD, causing it to fail to probe correctly.

The Surface Pro 11's DSDT table contains some XML with an
"EDPOverrideDPCDCaps" block that defines the max link rate as 0x1E
(8.1Gbps/HBR3).

Add a quirk to conditionally override the max link rate if its value
is zero specifically for this model.

Signed-off-by: Jérôme de Bretagne <jerome.debretagne@...il.com>
Signed-off-by: Dale Whinham <daleyo@...il.com>
---
 drivers/gpu/drm/msm/dp/dp_panel.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/gpu/drm/msm/dp/dp_panel.c b/drivers/gpu/drm/msm/dp/dp_panel.c
index 4e8ab75c771b..b2e65b987c05 100644
--- a/drivers/gpu/drm/msm/dp/dp_panel.c
+++ b/drivers/gpu/drm/msm/dp/dp_panel.c
@@ -11,6 +11,8 @@
 #include <drm/drm_of.h>
 #include <drm/drm_print.h>
 
+#include <linux/dmi.h>
+
 #define DP_MAX_NUM_DP_LANES	4
 #define DP_LINK_RATE_HBR2	540000 /* kbytes */
 
@@ -58,6 +60,17 @@ static int msm_dp_panel_read_dpcd(struct msm_dp_panel *msm_dp_panel)
 	if (rc)
 		return rc;
 
+	/*
+	 * for some reason the ATNA30DW01-1 OLED panel in the Surface Pro 11
+	 * reports a max link rate of 0 in the DPCD. Fix it to match the
+	 * EDPOverrideDPCDCaps string found in the ACPI DSDT
+	 */
+	if (dpcd[DP_MAX_LINK_RATE] == 0 &&
+	    dmi_match(DMI_SYS_VENDOR, "Microsoft Corporation") &&
+	    dmi_match(DMI_PRODUCT_NAME, "Microsoft Surface Pro, 11th Edition")) {
+		dpcd[1] = DP_LINK_BW_8_1;
+	}
+
 	msm_dp_panel->vsc_sdp_supported = drm_dp_vsc_sdp_supported(panel->aux, dpcd);
 	link_info = &msm_dp_panel->link_info;
 	link_info->revision = dpcd[DP_DPCD_REV];
-- 
2.50.1