linux-kernel - Re: [PATCH v2] gpio: sprd: Clear interrupt when setting the type as edge

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Message-ID: <CAMpxmJUwk9b=O4d6PEX_N39Eft1TEc1X2NQpuERQZWyPhz73-g@mail.gmail.com>
Date:   Mon, 31 Aug 2020 18:08:52 +0200
From:   Bartosz Golaszewski <bgolaszewski@...libre.com>
To:     Chunyan Zhang <zhang.lyra@...il.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        linux-gpio <linux-gpio@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Orson Zhai <orsonzhai@...il.com>,
        Baolin Wang <baolin.wang7@...il.com>,
        Chunyan Zhang <chunyan.zhang@...soc.com>,
        Taiping Lai <taiping.lai@...soc.com>
Subject: Re: [PATCH v2] gpio: sprd: Clear interrupt when setting the type as edge

On Mon, Aug 31, 2020 at 11:10 AM Chunyan Zhang <zhang.lyra@...il.com> wrote:
>
> From: Taiping Lai <taiping.lai@...soc.com>
>
> The raw interrupt status of GPIO maybe set before the interrupt is enabled,
> which would trigger the interrupt event once enabled it from user side.
> This is the case for edge interrupts only. Adding a clear operation when
> setting interrupt type can avoid that.
>
> There're a few considerations for the solution:
> 1) This issue is for edge interrupt only; The interrupts requested by users
>    are IRQ_TYPE_LEVEL_HIGH as default, so clearing interrupt when request
>    is useless.
> 2) The interrupt type can be set to edge when request and following up
>    with clearing it though, but the problem is still there once users set
>    the interrupt type to level trggier.
> 3) We can add a clear operation after each time of setting interrupt
>    enable bit, but it is redundant for level trigger interrupt.
>
> Therefore, the solution is this patch seems the best for now.
>
> Fixes: 9a3821c2bb47 ("gpio: Add GPIO driver for Spreadtrum SC9860 platform")
> Signed-off-by: Taiping Lai <taiping.lai@...soc.com>
> Signed-off-by: Chunyan Zhang <chunyan.zhang@...soc.com>
> ---
> * Changes since v1:
> - Rebased on v5.9-rc1.
> ---
>  drivers/gpio/gpio-sprd.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpio/gpio-sprd.c b/drivers/gpio/gpio-sprd.c
> index d7314d39ab65..36ea8a3bd451 100644
> --- a/drivers/gpio/gpio-sprd.c
> +++ b/drivers/gpio/gpio-sprd.c
> @@ -149,17 +149,20 @@ static int sprd_gpio_irq_set_type(struct irq_data *data,
>                 sprd_gpio_update(chip, offset, SPRD_GPIO_IS, 0);
>                 sprd_gpio_update(chip, offset, SPRD_GPIO_IBE, 0);
>                 sprd_gpio_update(chip, offset, SPRD_GPIO_IEV, 1);
> +               sprd_gpio_update(chip, offset, SPRD_GPIO_IC, 1);
>                 irq_set_handler_locked(data, handle_edge_irq);
>                 break;
>         case IRQ_TYPE_EDGE_FALLING:
>                 sprd_gpio_update(chip, offset, SPRD_GPIO_IS, 0);
>                 sprd_gpio_update(chip, offset, SPRD_GPIO_IBE, 0);
>                 sprd_gpio_update(chip, offset, SPRD_GPIO_IEV, 0);
> +               sprd_gpio_update(chip, offset, SPRD_GPIO_IC, 1);
>                 irq_set_handler_locked(data, handle_edge_irq);
>                 break;
>         case IRQ_TYPE_EDGE_BOTH:
>                 sprd_gpio_update(chip, offset, SPRD_GPIO_IS, 0);
>                 sprd_gpio_update(chip, offset, SPRD_GPIO_IBE, 1);
> +               sprd_gpio_update(chip, offset, SPRD_GPIO_IC, 1);
>                 irq_set_handler_locked(data, handle_edge_irq);
>                 break;
>         case IRQ_TYPE_LEVEL_HIGH:
> --
> 2.20.1
>

Queued for fixes, thanks!

Bartosz