linux-kernel - Re: [RFC PATCH] pinctrl: rockchip: add irq

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Message-ID: <20170629220532.GA54678@google.com>
Date:   Thu, 29 Jun 2017 15:05:33 -0700
From:   Brian Norris <briannorris@...omium.org>
To:     Jeffy Chen <jeffy.chen@...k-chips.com>
Cc:     linux-kernel@...r.kernel.org, tfiga@...omium.org, heiko@...ech.de,
        dianders@...omium.org, linux-rockchip@...ts.infradead.org,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-gpio@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC PATCH] pinctrl: rockchip: add irq_shutdown

On Fri, Jun 23, 2017 at 09:03:39PM +0800, Jeffy Chen wrote:
> Currently the rockchip pinctrl driver would try to enable/disable the
> gpio bank clk when enable/disable an irq.
> 
> So when the irq core trying to shutdown an already disabled irq, it
> would result in unbalanced clk disable request:
> [   35.911955] WARNING: at drivers/clk/clk.c:680
> ...
> [   37.272271] Call trace:
> [   37.274729] [<ffffffc0007ac270>] clk_core_disable+0x28/0x194
> [   37.280395] [<ffffffc0007ac6a8>] clk_disable+0x34/0x48
> [   37.285544] [<ffffffc0004f3bf0>] rockchip_irq_disable+0x30/0x3c
> [   37.291472] [<ffffffc00027a7e0>] __irq_disable+0x40/0x64
> [   37.296791] [<ffffffc00027a86c>] irq_shutdown+0x68/0x8c
> [   37.302023] [<ffffffc0002777fc>] __free_irq+0x110/0x218
> [   37.307254] [<ffffffc0002779a8>] free_irq+0x54/0x64
> [   37.312138] [<ffffffc00027ba24>] devm_irq_release+0x24/0x30
> 
> Add an irq_shutdown callback, and do a sanity check for irq state to
> prevent that.

IMO, this patch is completely the wrong approach. Either we:

(a) follow the current semantics of the irqchip core handling (which
tglx described more or less as "no refcounting; no guarantee that
enable/disable are balanced") or

(b) fix the irqchip core to provide the above guarantee

To do (a) properly would be rather trivial too; just keep an extra
bitmask in the bank struct to track the "enabled" state of each
interrupt. If the mask is non-zero, enable the clock; if zero, disable.
(Incidentally, this is pretty similar logic to what you ended up with on
your SPI runtime PM / set_cs() patches recently.)

This patch does neither (a) nor (b), and so I'd tend to reject it.

Brian

> Signed-off-by: Jeffy Chen <jeffy.chen@...k-chips.com>
> ---
> 
>  drivers/pinctrl/pinctrl-rockchip.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/pinctrl/pinctrl-rockchip.c b/drivers/pinctrl/pinctrl-rockchip.c
> index 607f52c..b0e3130 100644
> --- a/drivers/pinctrl/pinctrl-rockchip.c
> +++ b/drivers/pinctrl/pinctrl-rockchip.c
> @@ -2551,6 +2551,12 @@ static void rockchip_irq_disable(struct irq_data *d)
>  	clk_disable(bank->clk);
>  }
>  
> +static void rockchip_irq_shutdown(struct irq_data *d)
> +{
> +	if (!irqd_irq_disabled(d))
> +		rockchip_irq_disable(d);
> +}
> +
>  static void rockchip_irq_bus_lock(struct irq_data *d)
>  {
>  	struct irq_chip_generic *gc = irq_data_get_irq_chip_data(d);
> @@ -2641,6 +2647,7 @@ static int rockchip_interrupts_register(struct platform_device *pdev,
>  		gc->chip_types[0].chip.irq_unmask = irq_gc_mask_clr_bit;
>  		gc->chip_types[0].chip.irq_enable = rockchip_irq_enable;
>  		gc->chip_types[0].chip.irq_disable = rockchip_irq_disable;
> +		gc->chip_types[0].chip.irq_shutdown = rockchip_irq_shutdown;
>  		gc->chip_types[0].chip.irq_set_wake = irq_gc_set_wake;
>  		gc->chip_types[0].chip.irq_suspend = rockchip_irq_suspend;
>  		gc->chip_types[0].chip.irq_resume = rockchip_irq_resume;
> -- 
> 2.1.4
> 
>