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From:   Bartosz Golaszewski <bgolaszewski@baylibre.com>
Date:   Thu, 2 Jan 2020 18:40:12 +0100
Message-ID: <CAMpxmJUWW6Ku7edG1WWz67sBiAj7Fxf_C=XWA3eNO=B75X7oOw@mail.gmail.com>
Subject: Re: [PATCH 2/8] gpio: zynq: protect direction in/out with a spinlock
To:     Srinivas Neeli <srinivas.neeli@xilinx.com>
Cc:     Linus Walleij <linus.walleij@linaro.org>,
        Michal Simek <michal.simek@xilinx.com>,
        shubhrajyoti.datta@xilinx.com,
        linux-gpio <linux-gpio@vger.kernel.org>,
        arm-soc <linux-arm-kernel@lists.infradead.org>,
        LKML <linux-kernel@vger.kernel.org>, git@xilinx.com
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czw., 26 gru 2019 o 13:12 Srinivas Neeli <srinivas.neeli@xilinx.com> napisa=
=C5=82(a):
>
> From: Glenn Langedock <Glenn.Langedock@barco.com>
>
> Fix race condition when changing the direction (in/out) of the GPIO pin.
> The read-modify-write sequence (as coded in the driver) isn't atomic and
> requires synchronization (spinlock).
>
> Signed-off-by: Glenn Langedock <Glenn.Langedock@barco.com>
> Signed-off-by: Michal Simek <michal.simek@xilinx.com>
> Signed-off-by: Srinivas Neeli <srinivas.neeli@xilinx.com>
> ---
>  drivers/gpio/gpio-zynq.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/drivers/gpio/gpio-zynq.c b/drivers/gpio/gpio-zynq.c
> index 05ba16fffdad..9c8b8a397a26 100644
> --- a/drivers/gpio/gpio-zynq.c
> +++ b/drivers/gpio/gpio-zynq.c
> @@ -10,6 +10,7 @@
>  #include <linux/gpio/driver.h>
>  #include <linux/init.h>
>  #include <linux/interrupt.h>
> +#include <linux/spinlock.h>
>  #include <linux/io.h>
>  #include <linux/module.h>
>  #include <linux/platform_device.h>
> @@ -116,6 +117,7 @@ struct gpio_regs {
>   * @irq:       interrupt for the GPIO device
>   * @p_data:    pointer to platform data
>   * @context:   context registers
> + * @dirlock:   lock used for direction in/out synchronization
>   */
>  struct zynq_gpio {
>         struct gpio_chip chip;
> @@ -124,6 +126,7 @@ struct zynq_gpio {
>         int irq;
>         const struct zynq_platform_data *p_data;
>         struct gpio_regs context;
> +       spinlock_t dirlock; /*lock used for direction in/out synchronizat=
ion */

Maybe just call it 'lock' in case it turns out other operations need
locking as well?

Bart