linux-kernel - [PATCH] drm/meson: fix TMDS clock filtering for DMT monitors

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Date:   Wed, 20 Mar 2019 09:11:10 +0100
From:   Neil Armstrong <narmstrong@...libre.com>
To:     daniel@...ll.ch
Cc:     dri-devel@...ts.freedesktop.org, linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Neil Armstrong <narmstrong@...libre.com>,
        Maxime Jourdan <mjourdan@...libre.com>
Subject: [PATCH] drm/meson: fix TMDS clock filtering for DMT monitors

DMT monitors does not necessarely report a maximum TMDS clock
in a VSDB EDID extension.

In this case, all modes are wrongly rejected, including
the DRM fallback EDID.

This patch only rejects modes whith clock > max_tmds_clock if
the max_tmds_clock is specified. This will only reject
4:2:0 HDMI2.0 modes, who reports a clock > max_tmds_clock.

Reported-by: Maxime Jourdan <mjourdan@...libre.com>
Fixes: d7d8fb7046b6 ("drm/meson: add HDMI div40 TMDS mode")
Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
---
 drivers/gpu/drm/meson/meson_dw_hdmi.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/meson/meson_dw_hdmi.c b/drivers/gpu/drm/meson/meson_dw_hdmi.c
index e28814f4ea6c..563953ec6ad0 100644
--- a/drivers/gpu/drm/meson/meson_dw_hdmi.c
+++ b/drivers/gpu/drm/meson/meson_dw_hdmi.c
@@ -569,7 +569,8 @@ dw_hdmi_mode_valid(struct drm_connector *connector,
 	DRM_DEBUG_DRIVER("Modeline " DRM_MODE_FMT "\n", DRM_MODE_ARG(mode));
 
 	/* If sink max TMDS clock, we reject the mode */
-	if (mode->clock > connector->display_info.max_tmds_clock)
+	if (connector->display_info.max_tmds_clock &&
+	    mode->clock > connector->display_info.max_tmds_clock)
 		return MODE_BAD;
 
 	/* Check against non-VIC supported modes */
-- 
2.21.0