Re: [PATCH 1/3] drm/msm/hdmi: Prevent gpio_free related kernel warnings

[Bjorn Andersson <bjorn.andersson@linaro.org>]

On Tue 19 Apr 03:56 PDT 2016, Archit Taneja wrote:

> Calling the legacy gpio_free on an invalid GPIO (a GPIO numbered -1)
> results in kernel warnings. This causes a lot of backtraces when
> we try to unload the drm/msm module.
> 
> Call gpio_free only on valid GPIOs.
> 
> Signed-off-by: Archit Taneja <architt@codeaurora.org>
> ---
>  drivers/gpu/drm/msm/hdmi/hdmi_connector.c | 19 ++++++++++++-------
>  1 file changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/hdmi/hdmi_connector.c b/drivers/gpu/drm/msm/hdmi/hdmi_connector.c
> index 26129bf..ce86117 100644
> --- a/drivers/gpu/drm/msm/hdmi/hdmi_connector.c
> +++ b/drivers/gpu/drm/msm/hdmi/hdmi_connector.c
> @@ -112,13 +112,16 @@ static int gpio_config(struct hdmi *hdmi, bool on)
>  		for (i = 0; i < HDMI_MAX_NUM_GPIO; i++) {
>  			struct hdmi_gpio_data gpio = config->gpios[i];
>  
> -			if (gpio.output) {
> -				int value = gpio.value ? 0 : 1;
> +			if (gpio.num != -1) {
> +				if (gpio.output) {
> +					int value = gpio.value ? 0 : 1;
>  
> -				gpio_set_value_cansleep(gpio.num, value);
> -			}
> +					gpio_set_value_cansleep(gpio.num,
> +								value);
> +				}
>  
> -			gpio_free(gpio.num);
> +				gpio_free(gpio.num);
> +			}
>  		};
>  
>  		DBG("gpio off");
> @@ -126,8 +129,10 @@ static int gpio_config(struct hdmi *hdmi, bool on)
>  
>  	return 0;
>  err:
> -	while (i--)
> -		gpio_free(config->gpios[i].num);
> +	while (i--) {
> +		if (config->gpios[i].num != -1)
> +			gpio_free(config->gpios[i].num);
> +	}
>  
>  	return ret;
>  }

The patch in itself looks good, but the bigger picture does not.

The ddc and hdp should be muxed to the hdmi block, so they should not
operated as gpios.

The mux seems more of a gpio so it should be made more explicit - i.e.
actually support muxing (if that's needed) rather than just setting hard
coded values.

And you should not gpio_request/free the gpio upon every usage, request
it during "probe time" and release it during "remove".

Regards,
Bjorn