[PATCH v2] drm/bridge: adv7511: Fix cec clock EPROBE_DEFER handling

[Laurent Pinchart]

Hi Vincent,

Thank you for the patch.

On Thu, Apr 30, 2020 at 01:54:39PM +0200, Vincent Whitchurch wrote:
> If adv7511's devm_clk_get() for the cec clock returns -EPROBE_DEFER, we
> end up in an infinite probe loop.  This happens:
> 
>  (1) adv7511's probe is called.
> 
>  (2) adv7511's probe adds some secondary i2c devices which bind to the
>  dummy driver and thus call driver_deferred_probe_trigger() and
>  increment deferred_trigger_count (see driver_bound()).
> 
>  (3) adv7511's probe returns -EPROBE_DEFER, and since the
>  deferred_trigger_count has changed during the probe call,
>  driver_deferred_probe_trigger() is called immediately (see
>  really_probe()) and adv7511's probe is scheduled.
> 
>  (4) Goto step 1.
> 
> [   61.972915] really_probe: bus: 'i2c': really_probe: probing driver adv7511 with device 0-0039
> [   61.992734] really_probe: bus: 'i2c': really_probe: probing driver dummy with device 0-003f
> [   61.993343] driver_bound: driver: 'dummy': driver_bound: bound to device '0-003f'
> [   61.993626] really_probe: bus: 'i2c': really_probe: bound device 0-003f to driver dummy
> [   61.995604] really_probe: bus: 'i2c': really_probe: probing driver dummy with device 0-0038
> [   61.996381] driver_bound: driver: 'dummy': driver_bound: bound to device '0-0038'
> [   61.996663] really_probe: bus: 'i2c': really_probe: bound device 0-0038 to driver dummy
> [   61.998651] really_probe: bus: 'i2c': really_probe: probing driver dummy with device 0-003c
> [   61.999222] driver_bound: driver: 'dummy': driver_bound: bound to device '0-003c'
> [   61.999496] really_probe: bus: 'i2c': really_probe: bound device 0-003c to driver dummy
> [   62.010050] really_probe: i2c 0-0039: Driver adv7511 requests probe deferral
> [   62.011380] really_probe: bus: 'platform': really_probe: probing driver pwm-clock with device clock-cec
> [   62.012812] really_probe: platform clock-cec: Driver pwm-clock requests probe deferral
> [   62.024679] really_probe: bus: 'i2c': really_probe: probing driver adv7511 with device 0-0039
> 
> Fix this by calling devm_clk_get() before registering the secondary
> devices.
> 
> Signed-off-by: Vincent Whitchurch <vincent.whitchurch at axis.com>
> ---
> v2: Add devm_clk_put() in error path.
> 
>  drivers/gpu/drm/bridge/adv7511/adv7511_cec.c | 31 ++++++++------------
>  drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 11 +++++--
>  2 files changed, 21 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_cec.c b/drivers/gpu/drm/bridge/adv7511/adv7511_cec.c
> index a20a45c0b353..f5e9d0b238d2 100644
> --- a/drivers/gpu/drm/bridge/adv7511/adv7511_cec.c
> +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_cec.c
> @@ -286,28 +286,17 @@ static const struct cec_adap_ops adv7511_cec_adap_ops = {
>  	.adap_transmit = adv7511_cec_adap_transmit,
>  };
>  
> -static int adv7511_cec_parse_dt(struct device *dev, struct adv7511 *adv7511)
> -{
> -	adv7511->cec_clk = devm_clk_get(dev, "cec");
> -	if (IS_ERR(adv7511->cec_clk)) {
> -		int ret = PTR_ERR(adv7511->cec_clk);
> -
> -		adv7511->cec_clk = NULL;
> -		return ret;
> -	}
> -	clk_prepare_enable(adv7511->cec_clk);
> -	adv7511->cec_clk_freq = clk_get_rate(adv7511->cec_clk);
> -	return 0;
> -}
> -
>  int adv7511_cec_init(struct device *dev, struct adv7511 *adv7511)
>  {
>  	unsigned int offset = adv7511->type == ADV7533 ?
>  						ADV7533_REG_CEC_OFFSET : 0;
> -	int ret = adv7511_cec_parse_dt(dev, adv7511);
> +	int ret;
>  
> -	if (ret)
> -		goto err_cec_parse_dt;
> +	if (!adv7511->cec_clk)
> +		goto err_cec_no_clock;
> +
> +	clk_prepare_enable(adv7511->cec_clk);
> +	adv7511->cec_clk_freq = clk_get_rate(adv7511->cec_clk);
>  
>  	adv7511->cec_adap = cec_allocate_adapter(&adv7511_cec_adap_ops,
>  		adv7511, dev_name(dev), CEC_CAP_DEFAULTS, ADV7511_MAX_ADDRS);
> @@ -342,8 +331,12 @@ int adv7511_cec_init(struct device *dev, struct adv7511 *adv7511)
>  err_cec_alloc:
>  	dev_info(dev, "Initializing CEC failed with error %d, disabling CEC\n",
>  		 ret);
> -err_cec_parse_dt:
> +	clk_disable_unprepare(adv7511->cec_clk);
> +	devm_clk_put(dev, adv7511->cec_clk);
> +	/* Ensure that adv7511_remove() doesn't attempt to disable it again. */
> +	adv7511->cec_clk = NULL;
> +err_cec_no_clock:
>  	regmap_write(adv7511->regmap, ADV7511_REG_CEC_CTRL + offset,
>  		     ADV7511_CEC_CTRL_POWER_DOWN);
> -	return ret == -EPROBE_DEFER ? ret : 0;
> +	return 0;

If this function can't fail anymore, I would make it void. With that,

Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

>  }
> diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> index 9e13e466e72c..ebc548e23ece 100644
> --- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> @@ -1122,6 +1122,15 @@ static int adv7511_probe(struct i2c_client *i2c, const struct i2c_device_id *id)
>  	if (ret)
>  		return ret;
>  
> +	adv7511->cec_clk = devm_clk_get(dev, "cec");
> +	if (IS_ERR(adv7511->cec_clk)) {
> +		ret = PTR_ERR(adv7511->cec_clk);
> +		if (ret == -EPROBE_DEFER)
> +			return ret;
> +
> +		adv7511->cec_clk = NULL;
> +	}
> +
>  	ret = adv7511_init_regulators(adv7511);
>  	if (ret) {
>  		dev_err(dev, "failed to init regulators\n");
> @@ -1226,8 +1235,6 @@ static int adv7511_probe(struct i2c_client *i2c, const struct i2c_device_id *id)
>  
>  err_unregister_cec:
>  	i2c_unregister_device(adv7511->i2c_cec);
> -	if (adv7511->cec_clk)
> -		clk_disable_unprepare(adv7511->cec_clk);
>  err_i2c_unregister_packet:
>  	i2c_unregister_device(adv7511->i2c_packet);
>  err_i2c_unregister_edid:

-- 
Regards,

Laurent Pinchart