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Subject: Re: [PATCH] GPIO, Fix bug where the wrong GPIO register is written to
To:     Paul Thomas <pthomas8589@gmail.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        Bartosz Golaszewski <bgolaszewski@baylibre.com>,
        Michal Simek <michal.simek@xilinx.com>,
        linux-gpio@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org,
        Shubhrajyoti Datta <shubhraj@xilinx.com>
References: <20200125221410.8022-1-pthomas8589@gmail.com>
From:   Michal Simek <michal.simek@xilinx.com>
Message-ID: <68610131-32f9-6ebb-705a-7d9303f21d3a@xilinx.com>
Date:   Mon, 27 Jan 2020 08:42:17 +0100
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On 25. 01. 20 23:14, Paul Thomas wrote:
> Care is taken with "index", however with the current version
> the actual xgpio_writereg is using index for data but
> xgpio_regoffset(chip, i) for the offset. And since i is already
> incremented it is incorrect. This patch fixes it so that index
> is used for the offset too.
> 
> Signed-off-by: Paul Thomas <pthomas8589@gmail.com>
> ---
>  There are many different ways to correct this, I'd just like it to get
>  fixed. I've tested this with a 5.2 kernel, but this patch is against
>  5.5rc7.
> 
>  drivers/gpio/gpio-xilinx.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpio/gpio-xilinx.c b/drivers/gpio/gpio-xilinx.c
> index a9748b5198e6..67f9f82e0db0 100644
> --- a/drivers/gpio/gpio-xilinx.c
> +++ b/drivers/gpio/gpio-xilinx.c
> @@ -147,9 +147,10 @@ static void xgpio_set_multiple(struct gpio_chip *gc, unsigned long *mask,
>  	for (i = 0; i < gc->ngpio; i++) {
>  		if (*mask == 0)
>  			break;
> +		/* Once finished with an index write it out to the register */
>  		if (index !=  xgpio_index(chip, i)) {
>  			xgpio_writereg(chip->regs + XGPIO_DATA_OFFSET +
> -				       xgpio_regoffset(chip, i),
> +				       index * XGPIO_CHANNEL_OFFSET,
>  				       chip->gpio_state[index]);
>  			spin_unlock_irqrestore(&chip->gpio_lock[index], flags);
>  			index =  xgpio_index(chip, i);
> @@ -165,7 +166,7 @@ static void xgpio_set_multiple(struct gpio_chip *gc, unsigned long *mask,
>  	}
>  
>  	xgpio_writereg(chip->regs + XGPIO_DATA_OFFSET +
> -		       xgpio_regoffset(chip, i), chip->gpio_state[index]);
> +		       index * XGPIO_CHANNEL_OFFSET, chip->gpio_state[index]);
>  
>  	spin_unlock_irqrestore(&chip->gpio_lock[index], flags);
>  }
> 

Shubhrajyoti: Please take a look.

Thanks,
Michal