[RFC][PATCH] drm: adv7511/33: Fix adv7511_cec_init() failure handling

[John Stultz]

From: Arnd Bergmann <arnd@xxxxxxxx>

An otherwise correct cleanup patch from Dan Carpenter turned a broken
failure handling from a feature patch by Hans Verkuil into a kernel
Oops, so bisection points to commit 7af35b0addbc ("drm/kirin: Checking
for IS_ERR() instead of NULL") rather than 3b1b975003e4 ("drm:
adv7511/33: add HDMI CEC support").

I've managed to piece together several partial problems, though
I'm still struggling with the bigger picture:

adv7511_probe() registers a drm_bridge structure that was allocated
with devm_kzalloc(). It calls adv7511_cec_init(), which fails for an
unknown reason, which in turn triggers the registered structure to be
removed.

Elsewhere, kirin_drm_platform_probe() gets called, which calls
of_graph_get_remote_node(), and that returns NULL. Before Dan's
patch we would go on with a NULL pointer here and register that,
now kirin_drm_platform_probe() fails with -ENODEV.

In a third driver, dsi_parse_dt() calls drm_of_find_panel_or_bridge(),
which after not finding a panel goes on to call of_drm_find_bridge(),
and that crashes due to the earlier list corruption.

This addresses the first issue by making sure that adv7511_probe()
does not completely fail when the adv7511_cec_init() function fails,
and instead we just disable the CEC feature. This avoids having the
driver entirely fail to load if just the CEC initialization fails.

Reported-by: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx>
Cc: Xinliang Liu <xinliang.liu@xxxxxxxxxx>
Cc: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Cc: Sean Paul <seanpaul@xxxxxxxxxxxx>
Cc: Hans Verkuil <hans.verkuil@xxxxxxxxx>
Cc: Archit Taneja <architt@xxxxxxxxxxxxxx>
Link: https://bugs.linaro.org/show_bug.cgi?id=3345
Link: https://lkft.validation.linaro.org/scheduler/job/48017#L3551
Fixes: 7af35b0addbc ("drm/kirin: Checking for IS_ERR() instead of NULL")
Fixes: 3b1b975003e4 ("drm: adv7511/33: add HDMI CEC support")
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
[jstultz: Reworked so when adv7511_cec_init() fails, we disable the feature instead
of disabling the entire driver, which causes graphics to not funciton]
Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
---
Just wanted to send out my rework of Arnd's patch here.
Feedback would be welcome.

thanks
-john

 drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
index 0e14f15..939c3b9 100644
--- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
+++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
@@ -1203,12 +1203,12 @@ static int adv7511_probe(struct i2c_client *i2c, const struct i2c_device_id *id)
 
 #ifdef CONFIG_DRM_I2C_ADV7511_CEC
 	ret = adv7511_cec_init(dev, adv7511, offset);
-	if (ret)
-		goto err_unregister_cec;
 #else
-	regmap_write(adv7511->regmap, ADV7511_REG_CEC_CTRL + offset,
-		     ADV7511_CEC_CTRL_POWER_DOWN);
+	ret = 1;
 #endif
+	if (ret)
+		regmap_write(adv7511->regmap, ADV7511_REG_CEC_CTRL + offset,
+			     ADV7511_CEC_CTRL_POWER_DOWN);
 
 	return 0;
 
-- 
2.7.4