linux-kernel - Re: [PATCH] gpio: zynq: Implement irq_(request|release)

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Message-ID: <CACRpkdYjNWiEdM8kthMXhGXBPYE74hy_xa7bBB6XQrAOaBnehA@mail.gmail.com>
Date:	Tue, 27 Oct 2015 17:23:33 +0100
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Grygorii Strashko <grygorii.strashko@...com>
Cc:	Soren Brinkmann <soren.brinkmann@...inx.com>,
	Alexandre Courbot <gnurou@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Michal Simek <michal.simek@...inx.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	John Linn <linnj@...inx.com>
Subject: Re: [PATCH] gpio: zynq: Implement irq_(request|release)_resources

On Tue, Oct 27, 2015 at 5:18 PM, Grygorii Strashko
<grygorii.strashko@...com> wrote:
> On 10/27/2015 05:53 PM, Linus Walleij wrote:
>>
>> On Fri, Oct 23, 2015 at 3:36 PM, Soren Brinkmann
>> <soren.brinkmann@...inx.com> wrote:
>>
>>> The driver uses runtime PM to leverage low power techniques. For
>>> use-cases using GPIO as interrupt the device needs to be in an
>>> appropriate state.
>>>
>>> Reported-by: John Linn <linnj@...inx.com>
>>> Signed-off-by: Soren Brinkmann <soren.brinkmann@...inx.com>
>>> Tested-by: John Linn <linnj@...inx.com>
>>
>>
>> As pointed out by Grygorii in
>> commit aca82d1cbb49af34b69ecd4571a0fe48ad9247c1:
>>
>>      The PM runtime API can't be used in atomic contex on -RT even if
>>      it's configured as irqsafe. As result, below error report can
>>      be seen when PM runtime API called from IRQ chip's callbacks
>>      irq_startup/irq_shutdown/irq_set_type, because they are
>>      protected by RAW spinlock:
>> (...)
>>      The IRQ chip interface defines only two callbacks which are executed
>> in
>>      non-atomic contex - irq_bus_lock/irq_bus_sync_unlock, so lets move
>>      PM runtime calls there.
>>
>> I.e. these calls are atomic context and it's just luck that it works
>> and this is fragile.
>>
>> Can you please check if you can move it to
>> irq_bus_lock()/irq_sync_unlock()
>> like Grygorii does?
>>
>
> This patch rises the question not only about PM runtime, but also
> about gpiochip_irq_reqres()/gpiochip_irq_relres().

Do you mean that these functions contain calls to non-atomic
functions?

I mainly reacted to this because it was pm_* calls, that you
mentioned explicitly in your patch.

Yours,
Linus Walleij
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