linux-kernel - Re: [PATCH] pinctrl: mcp23s08: Get rid of spurious level interrupts

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Message-ID: <CALieaef39VdmjF=e+65bqF6_dkq7sT1-ps1X3gAnq-Gy6Huodg@mail.gmail.com>
Date: Fri, 7 Feb 2025 23:40:53 +0300
From: Dmitry Mastykin <mastichi@...il.com>
To: Linus Walleij <linus.walleij@...aro.org>
Cc: Sebastian Reichel <sre@...nel.org>, linux-gpio@...r.kernel.org, 
	linux-kernel@...r.kernel.org, e.shatokhin@...ro.com, 
	arturas.moskvinas@...il.com
Subject: Re: [PATCH] pinctrl: mcp23s08: Get rid of spurious level interrupts

Hi Linus,
thank you for the answer.
I made more tests and think that this patch shouldn't be applied.
It removes duplicated interrupts, but sometimes they increase the performance:
a new interrupt may come during handling a spurious one, and a
spurious one will become valid (resulting in a kind of polling). I see
the number of my touchscreen interrupts reduced from 200 to 130 per
second with this patch. It may be a bigger problem for users, than
duplicated interrupts. Sorry.

Kind regards,
Dmitry

On Thu, Feb 6, 2025 at 12:26 PM Linus Walleij <linus.walleij@...aro.org> wrote:
>
> On Wed, Jan 22, 2025 at 1:05 PM Dmitry Mastykin <mastichi@...il.com> wrote:
>
> > irq_mask()/irq_unmask() are not called for nested interrupts. So level
> > interrupts are never masked, chip's interrupt output is not cleared on
> > INTCAP or GPIO read, the irq handler is uselessly called again. Nested
> > irq handler is not called again, because interrupt reason is cleared by
> > its first call.
> > /proc/interrupts shows that number of chip's irqs is greater than
> > number of nested irqs.
> >
> > This patch adds masking and unmasking level interrupts inside irq handler.
> >
> > Signed-off-by: Dmitry Mastykin <mastichi@...il.com>
>
> Patch tentatively applied as non-urgent fix.
>
> If this is urgent, I need a Fixes: tags and we should also tag it
> for stable, is this a big problem for users? I don't have the big picture
> here.
>
> Adding Sebastian, if he's still using this expander.
>
> Yours,
> Linus Walleij