linux-kernel - Re: [PATCH 1/1] gpio: twl4030: Fix regression for twl gpio LED output

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Date:	Wed, 4 Dec 2013 09:37:05 -0800
From:	Tony Lindgren <tony@...mide.com>
To:	Roger Quadros <rogerq@...com>
Cc:	linus.walleij@...aro.org, peter.ujfalusi@...com, nm@...com,
	tomi.valkeinen@...com, balbi@...com, linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/1] gpio: twl4030: Fix regression for twl gpio LED
 output

* Roger Quadros <rogerq@...com> [131204 03:35]:
> Commit 0b2aa8be introduced a regression that causes failure
> in setting LED GPO direction to OUT.
> 
> This causes USB host probe failures for Beagleboard C4.
> 
> [    2.075469] platform usb_phy_gen_xceiv.2: Driver usb_phy_gen_xceiv requests probe deferral
> [    2.090454] hsusb2_vcc: Failed to request enable GPIO510: -22
> [    2.100982] reg-fixed-voltage reg-fixed-voltage.0.auto: Failed to register regulator: -22
> [    2.109954] reg-fixed-voltage: probe of reg-fixed-voltage.0.auto failed with error -22
> 
> direction_out/direction_in must return 0 if the operation succeeded.

Uh, OK, sorry that was an unexpected side effect. We still should keep the
return values though instead of just ignoring them.
 
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpio/gpio-twl4030.c b/drivers/gpio/gpio-twl4030.c
> index b97d6a6..0999ed1 100644
> --- a/drivers/gpio/gpio-twl4030.c
> +++ b/drivers/gpio/gpio-twl4030.c
> @@ -294,13 +294,13 @@ out:
>  static int twl_direction_in(struct gpio_chip *chip, unsigned offset)
>  {
>  	struct gpio_twl4030_priv *priv = to_gpio_twl4030(chip);
> -	int ret;
> +	int ret = 0;
>  
>  	mutex_lock(&priv->mutex);
>  	if (offset < TWL4030_GPIO_MAX)
> -		ret = twl4030_set_gpio_direction(offset, 1);
> +		twl4030_set_gpio_direction(offset, 1);
>  	else
> -		ret = -EINVAL;
> +		ret = -EINVAL;	/* LED outputs can't be set as input */
>  
>  	if (!ret)
>  		priv->direction &= ~BIT(offset);

This looks OK to me.

> @@ -354,18 +354,21 @@ static void twl_set(struct gpio_chip *chip, unsigned offset, int value)
>  static int twl_direction_out(struct gpio_chip *chip, unsigned offset, int value)
>  {
>  	struct gpio_twl4030_priv *priv = to_gpio_twl4030(chip);
> -	int ret = -EINVAL;
>  

Can't you just have:

	int ret = 0;

>  	mutex_lock(&priv->mutex);
>  	if (offset < TWL4030_GPIO_MAX)
> -		ret = twl4030_set_gpio_direction(offset, 0);
> +		twl4030_set_gpio_direction(offset, 0);
> +
> +	/*
> +	 *  LED gpio's i.e. offset >= TWL4030_GPIO_MAX are always output
> +	 */
>  
>  	priv->direction |= BIT(offset);
>  	mutex_unlock(&priv->mutex);
>  
>  	twl_set(chip, offset, value);
>  
> -	return ret;
> +	return 0;
>  }

Then the rest of this change is not needed and we check the return value for
twl4030_set_gpio_direction. Makes sense to keep the comment there though.

Regards,

Tony
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