linux-kernel - Re: [PATCH] [RFT] drm: adv7511/33: fix adv7511_cec

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Date:   Wed, 15 Nov 2017 13:58:32 +0100
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Arnd Bergmann <arnd@...db.de>,
        Archit Taneja <architt@...eaurora.org>
Cc:     Bhumika Goyal <bhumirks@...il.com>,
        David Airlie <airlied@...ux.ie>, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        Hans Verkuil <hans.verkuil@...co.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [PATCH] [RFT] drm: adv7511/33: fix adv7511_cec_init() failure
 handling

On 15/11/17 13:37, Arnd Bergmann wrote:
> 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 leave behind any corrupted list entries. This should
> get the system back to boot but needs testing. From my understanding,
> there is at least one more bug that needs to be resolved to actually
> get everything to work again.
> 
> Reported-by: Naresh Kamboju <naresh.kamboju@...aro.org>
> Cc: Xinliang Liu <xinliang.liu@...aro.org>
> Cc: Dan Carpenter <dan.carpenter@...cle.com>
> Cc: Sean Paul <seanpaul@...omium.org>
> Cc: Hans Verkuil <hans.verkuil@...co.com>
> Cc: Archit Taneja <architt@...eaurora.org>
> 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@...db.de>
> ---
> Untested so far, this is what I came up with after reading the
> WARN_ON log from a modified kernel.
> 
> Naresh, can you give this one a go?
> 
> Hans and others, can you review in the meantime?
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> index 0e14f1572d05..93d1ecafe8fa 100644
> --- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> @@ -1204,7 +1204,7 @@ 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;
> +		goto err_unregister_bridge;

Rather than adding the err_unregister_bridge label, I think it is better to move
this code up to just before the call to drm_bridge_add().

I think I just didn't realize that doing it after would require additional cleanup.
But it should be perfectly fine to move it up so we can avoid doing that.

I can't test it until Monday as I don't have access to the hardware at the moment.

Regards,

	Hans

>  #else
>  	regmap_write(adv7511->regmap, ADV7511_REG_CEC_CTRL + offset,
>  		     ADV7511_CEC_CTRL_POWER_DOWN);
> @@ -1212,6 +1212,11 @@ static int adv7511_probe(struct i2c_client *i2c, const struct i2c_device_id *id)
>  
>  	return 0;
>  
> +#ifdef CONFIG_DRM_I2C_ADV7511_CEC
> +err_unregister_bridge:
> +	adv7511_audio_exit(adv7511);
> +	drm_bridge_remove(&adv7511->bridge);
> +#endif
>  err_unregister_cec:
>  	i2c_unregister_device(adv7511->i2c_cec);
>  	if (adv7511->cec_clk)
>