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From:   Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To:     Hans Verkuil <hverkuil@xs4all.nl>
Cc:     Arnd Bergmann <arnd@arndb.de>, Bhumika Goyal <bhumirks@gmail.com>,
        David Airlie <airlied@linux.ie>,
        lkml <linux-kernel@vger.kernel.org>,
        dri-devel@lists.freedesktop.org,
        Hans Verkuil <hans.verkuil@cisco.com>,
        Dan Carpenter <dan.carpenter@oracle.com>,
        John Stultz <john.stultz@linaro.org>
Subject: Re: [PATCHv2] drm: adv7511/33: Fix adv7511_cec_init() failure handling
Date:   Tue, 21 Nov 2017 08:48:01 +0200
Message-ID: <2716873.T4RGvjZqqn@avalon>
Organization: Ideas on Board Oy
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Hi Hans,

Thank you for the patch.

On Monday, 20 November 2017 22:57:34 EET Hans Verkuil wrote:
> If the device tree for a board did not specify a cec clock, then
> adv7511_cec_init would return an error, which would cause adv7511_probe()
> to fail and thus there is no HDMI output.
> 
> There is no need to have adv7511_probe() fail if the CEC initialization
> fails, so just change adv7511_cec_init() to a void function. In addition,
> adv7511_cec_init() should just return silently if the cec clock isn't
> found and show a message for any other errors.

I don't think that's correct. You at least need to defer probing if the clock 
is specified in DT but has no provider available yet. For other errors I agree 
that we can still initialize the ADV7511 in a degraded mode without CEC 
support, although I would prefer to also error out in case of invalid DT to 
ensure that DT errors are caught as early as possible.

> An otherwise correct cleanup patch from Dan Carpenter turned this broken
> failure handling 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").
> 
> Based on earlier patches from Arnd and John.
> 
> Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
> Cc: Xinliang Liu <xinliang.liu@linaro.org>
> Cc: Dan Carpenter <dan.carpenter@oracle.com>
> Cc: Sean Paul <seanpaul@chromium.org>
> Cc: Archit Taneja <architt@codeaurora.org>
> Cc: John Stultz <john.stultz@linaro.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: Hans Verkuil <hans.verkuil@cisco.com>
> Tested-by: Hans Verkuil <hans.verkuil@cisco.com>
> ---
> This rework of Arnd and John's patches goes a bit further and makes
> cec_init a void function and just silently exits if there is no cec clock
> defined in the dts. I'm sure that's the reason why the kirin board failed
> on this. BTW: if the kirin board DOES support cec, then it would be nice
> if it can be hooked up in the dts!
> 
> Tested with my Dragonboard and Renesas Koelsch board.
> 
> Change since my previous RFC PATCH:
> 
> - added static inline adv7511_cec_init to avoid #ifdef in the probe function
> as suggested by John Stultz.
> 
> Regards,
> 
> 	Hans
> ---
> diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511.h
> b/drivers/gpu/drm/bridge/adv7511/adv7511.h index 543a5eb91624..16051bfa5578
> 100644
> --- a/drivers/gpu/drm/bridge/adv7511/adv7511.h
> +++ b/drivers/gpu/drm/bridge/adv7511/adv7511.h
> @@ -374,9 +374,17 @@ struct adv7511 {
>  };
> 
>  #ifdef CONFIG_DRM_I2C_ADV7511_CEC
> -int adv7511_cec_init(struct device *dev, struct adv7511 *adv7511,
> -		     unsigned int offset);
> +void adv7511_cec_init(struct device *dev, struct adv7511 *adv7511,
> +		      unsigned int offset);
>  void adv7511_cec_irq_process(struct adv7511 *adv7511, unsigned int irq1);
> +#else
> +static inline void adv7511_cec_init(struct device *dev,
> +				    struct adv7511 *adv7511,
> +				    unsigned int offset)
> +{
> +	regmap_write(adv7511->regmap, ADV7511_REG_CEC_CTRL + offset,
> +		     ADV7511_CEC_CTRL_POWER_DOWN);
> +}
>  #endif
> 
>  #ifdef CONFIG_DRM_I2C_ADV7533
> diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_cec.c
> b/drivers/gpu/drm/bridge/adv7511/adv7511_cec.c index
> b33d730e4d73..c1cd471d31fa 100644
> --- a/drivers/gpu/drm/bridge/adv7511/adv7511_cec.c
> +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_cec.c
> @@ -300,18 +300,20 @@ static int adv7511_cec_parse_dt(struct device *dev,
> struct adv7511 *adv7511) return 0;
>  }
> 
> -int adv7511_cec_init(struct device *dev, struct adv7511 *adv7511,
> -		     unsigned int offset)
> +void adv7511_cec_init(struct device *dev, struct adv7511 *adv7511,
> +		      unsigned int offset)
>  {
>  	int ret = adv7511_cec_parse_dt(dev, adv7511);
> 
>  	if (ret)
> -		return ret;
> +		goto disable_cec;
> 
>  	adv7511->cec_adap = cec_allocate_adapter(&adv7511_cec_adap_ops,
>  		adv7511, dev_name(dev), CEC_CAP_DEFAULTS, ADV7511_MAX_ADDRS);
> -	if (IS_ERR(adv7511->cec_adap))
> -		return PTR_ERR(adv7511->cec_adap);
> +	if (IS_ERR(adv7511->cec_adap)) {
> +		ret = PTR_ERR(adv7511->cec_adap);
> +		goto fail;
> +	}
> 
>  	regmap_write(adv7511->regmap, ADV7511_REG_CEC_CTRL + offset, 0);
>  	/* cec soft reset */
> @@ -329,9 +331,15 @@ int adv7511_cec_init(struct device *dev, struct adv7511
> *adv7511, ((adv7511->cec_clk_freq / 750000) - 1) << 2);
> 
>  	ret = cec_register_adapter(adv7511->cec_adap, dev);
> -	if (ret) {
> -		cec_delete_adapter(adv7511->cec_adap);
> -		adv7511->cec_adap = NULL;
> -	}
> -	return ret;
> +	if (!ret)
> +		return;

This confused me for an instant, I think a goto error_cec_delete would be 
clearer, but that's up to you (maybe I just wasn't awake enough).

> +	cec_delete_adapter(adv7511->cec_adap);
> +	adv7511->cec_adap = NULL;
> +
> +fail:

Nitpicking, I'd name this error to match the labels in the probe function.

> +	dev_info(dev, "Initializing CEC failed with error %d, disabling CEC\n",
> +		 ret);
> +disable_cec:
> +	regmap_write(adv7511->regmap, ADV7511_REG_CEC_CTRL + offset,
> +		     ADV7511_CEC_CTRL_POWER_DOWN);
>  }
> diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c index
> 3a33075dbb22..2eb465827bcd 100644
> --- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> @@ -1200,15 +1200,7 @@ static int adv7511_probe(struct i2c_client *i2c,
> const struct i2c_device_id *id) adv7511_audio_init(dev, adv7511);
> 
>  	offset = adv7511->type == ADV7533 ? ADV7533_REG_CEC_OFFSET : 0;
> -
> -#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);
> -#endif
> +	adv7511_cec_init(dev, adv7511, offset);

Now that the offset is only passed to this function, how about computing it in 
adv7511_cec_init() to store as much CEC code as possible in drivers/gpu/drm/
bridge/adv7511/adv7511_cec.c ?

> 
>  	return 0;

-- 
Regards,

Laurent Pinchart


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