linux-kernel - Re: [PATCH] gpio: pca953x: Fix warning when HW interrupts are rescheduled by the softirq tasklet

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Date:	Tue, 23 Sep 2014 14:04:10 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Lothar Waßmann <LW@...o-electronics.de>
Cc:	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Alexandre Courbot <gnurou@...il.com>
Subject: Re: [PATCH] gpio: pca953x: Fix warning when HW interrupts are
 rescheduled by the softirq tasklet

On Tue, Sep 9, 2014 at 10:32 AM, Lothar Waßmann <LW@...o-electronics.de> wrote:

> When using e.g. the matrix_keymap driver with the gpio-pca953x driver,
> the following warning may be issued when a keypress is detected:
> WARNING: CPU: 0 PID: 3 at kernel/irq/manage.c:677 irq_nested_primary_handler+0x18/0x2c()
> Primary handler called for nested irq 245
> Modules linked in: evbug ci_hdrc_imx usbmisc_imx ci_hdrc udc_core ehci_hcd phy_mxs_usb
> CPU: 0 PID: 3 Comm: ksoftirqd/0 Tainted: G        W     3.16.0-karo+ #118
> [<c00142cc>] (unwind_backtrace) from [<c00118f8>] (show_stack+0x10/0x14)
> [<c00118f8>] (show_stack) from [<c001bf10>] (warn_slowpath_common+0x64/0x84)
> [<c001bf10>] (warn_slowpath_common) from [<c001bfc4>] (warn_slowpath_fmt+0x30/0x40)
> [<c001bfc4>] (warn_slowpath_fmt) from [<c004ce08>] (irq_nested_primary_handler+0x18/0x2c)
> [<c004ce08>] (irq_nested_primary_handler) from [<c004cb80>] (handle_irq_event_percpu+0x50/0x168)
> [<c004cb80>] (handle_irq_event_percpu) from [<c004ccf8>] (handle_irq_event+0x60/0x7c)
> [<c004ccf8>] (handle_irq_event) from [<c004f02c>] (handle_simple_irq+0x78/0xdc)
> [<c004f02c>] (handle_simple_irq) from [<c004ed14>] (resend_irqs+0x4c/0x78)
> [<c004ed14>] (resend_irqs) from [<c001f3ec>] (tasklet_action+0x74/0xd8)
> [<c001f3ec>] (tasklet_action) from [<c001f760>] (__do_softirq+0xd0/0x1f4)
> [<c001f760>] (__do_softirq) from [<c001f8c4>] (run_ksoftirqd+0x40/0x64)
> [<c001f8c4>] (run_ksoftirqd) from [<c003d464>] (smpboot_thread_fn+0x174/0x234)
> [<c003d464>] (smpboot_thread_fn) from [<c0036dd4>] (kthread+0xb4/0xd0)
> [<c0036dd4>] (kthread) from [<c000f0f0>] (ret_from_fork+0x14/0x24)
> ---[ end trace a68cf7bc5348c4f7 ]---
>
> This happens when an IRQ is detected by the GPIO driver while the GPIO
> client driver (matrix_keypad in this case) has disabled the irq for
> the GPIO it has acquired. When the HW IRQ is being rescheduled by the
> softirq thread, the primary IRQ handler is called for the nested IRQ
> registered by the client driver rather than for the parent IRQ from
> the GPIO driver.
>
> This patch makes sure, that the parent_irq (gpio-pca953x) is
> rescheduled rather than the nested irq registered by the matrix_keypad
> driver.
> Similar patches are most probably required for a bunch of other
> drivers too.
>
> Signed-off-by: Lothar Waßmann <LW@...O-electronics.de>
> ---
>  drivers/gpio/gpio-pca953x.c |   12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-pca953x.c
> index e2da64a..770ef6b 100644
> --- a/drivers/gpio/gpio-pca953x.c
> +++ b/drivers/gpio/gpio-pca953x.c
> @@ -518,6 +518,7 @@ static int pca953x_irq_setup(struct pca953x_chip *chip,
>                              int irq_base)
>  {
>         struct i2c_client *client = chip->client;
> +       struct gpio_chip *gpio_chip = &chip->gpio_chip;
>         int ret, i, offset = 0;
>
>         if (client->irq && irq_base != -1
> @@ -567,6 +568,17 @@ static int pca953x_irq_setup(struct pca953x_chip *chip,
>                                 "could not connect irqchip to gpiochip\n");
>                         return ret;
>                 }
> +
> +               for (i = 0; i < NBANK(chip); i++) {
> +                       int j;
> +
> +                       for (j = 0; j < BANK_SZ; j++) {
> +                               int gpio = gpio_chip->base + i * BANK_SZ + j;
> +                               int irq = gpio_to_irq(gpio);
> +
> +                               irq_set_parent(irq, client->irq);
> +                       }
> +               }

While this is fixing the problem, but isn't the right fix to patch
the function gpiochip_irq_map() in gpiolib.c to call
irq_set_parent() for each IRQ as it gets mapped?

This driver is using the gpiolib irqchip helpers...

Then you fix not just this driver but all drivers, plus the complex
loop and calls to gpio_to_irq() etc goes away.

Yours,
Linus Walleij
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