Patch "drm/mediatek: hdmi: Perform NULL pointer check for mtk_hdmi_conf" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    drm/mediatek: hdmi: Perform NULL pointer check for mtk_hdmi_conf

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     drm-mediatek-hdmi-perform-null-pointer-check-for-mtk.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit a7c7c0746b8a97d4903118ad6990fd04d4c58175
Author: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
Date:   Thu Oct 28 09:43:11 2021 +0200

    drm/mediatek: hdmi: Perform NULL pointer check for mtk_hdmi_conf
    
    [ 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@xxxxxxxxxxxxx>
    Signed-off-by: Chun-Kuang Hu <chunkuang.hu@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

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;