[PATCH 5.15 015/128] drm/mediatek: hdmi: Perform NULL pointer check for mtk_hdmi_conf

Greg Kroah-Hartman
2021-12-27T15:45:52Z

From: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

[ Upstream commit 3b8e19a0aa3933a785be9f1541afd8d398c4ec69 ]

In commit 41ca9caaae0b
("drm/mediatek: hdmi: Add check for CEA modes only") a check
for CEA modes was added to function mtk_hdmi_bridge_mode_valid()
in order to address possible issues on MT8167;
moreover, with commit c91026a938c2
("drm/mediatek: hdmi: Add optional limit on maximal HDMI mode clock")
another similar check was introduced.

Unfortunately though, at the time of writing, MT8173 does not provide
any mtk_hdmi_conf structure and this is crashing the kernel with NULL
pointer upon entering mtk_hdmi_bridge_mode_valid(), which happens as
soon as a HDMI cable gets plugged in.

To fix this regression, add a NULL pointer check for hdmi->conf in the
said function, restoring HDMI functionality and avoiding NULL pointer
kernel panics.

Fixes: 41ca9caaae0b ("drm/mediatek: hdmi: Add check for CEA modes only")
Fixes: c91026a938c2 ("drm/mediatek: hdmi: Add optional limit on maximal HDMI mode clock")
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/mediatek/mtk_hdmi.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_hdmi.c b/drivers/gpu/drm/mediatek/mtk_hdmi.c
index 5838c44cbf6f0..3196189429bcf 100644
--- a/drivers/gpu/drm/mediatek/mtk_hdmi.c
+++ b/drivers/gpu/drm/mediatek/mtk_hdmi.c
@@ -1224,12 +1224,14 @@ static int mtk_hdmi_bridge_mode_valid(struct drm_bridge *bridge,
return MODE_BAD;
}

- if (hdmi->conf->cea_modes_only && !drm_match_cea_mode(mode))
- return MODE_BAD;
+ if (hdmi->conf) {
+ if (hdmi->conf->cea_modes_only && !drm_match_cea_mode(mode))
+ return MODE_BAD;

- if (hdmi->conf->max_mode_clock &&
- mode->clock > hdmi->conf->max_mode_clock)
- return MODE_CLOCK_HIGH;
+ if (hdmi->conf->max_mode_clock &&
+ mode->clock > hdmi->conf->max_mode_clock)
+ return MODE_CLOCK_HIGH;
+ }

if (mode->clock < 27000)
return MODE_CLOCK_LOW;
--
2.34.1