linux-kernel - Re: [PATCH] pinctrl: amd: Set up affinity for GPIO lines when enabling interrupt

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Message-ID: <ZksaCG3Q5qHthNcN@smile.fi.intel.com>
Date: Mon, 20 May 2024 12:38:16 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Mario Limonciello <mario.limonciello@....com>
Cc: Shyam-sundar.S-k@....com, linus.walleij@...aro.org,
	Basavaraj.Natikar@....com, linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org, Hans de Goede <hdegoede@...hat.com>,
	Kieran Levin <ktl@...me.work>
Subject: Re: [PATCH] pinctrl: amd: Set up affinity for GPIO lines when
 enabling interrupt

On Sun, May 19, 2024 at 07:41:09AM -0500, Mario Limonciello wrote:
> When a touchpad's attention interrupt is triggered on a different
> CPU than the GPIO controller interrupt multiple CPUs wake up the system
> and can cause higher power consumption than necessary for operating
> the touchpad.
> 
> Waking up the additional CPUs is especially unnecessary as the
> irq_ack() callback for pinctrl-amd doesn't do anything.
> 
> To solve this save the affinity of the GPIO controller interrupt when
> it's set up and assign that affinity to the GPIO line IRQ.

I do not much care about AMD :-) case but I think this is quite a big hammer
with possible undesired effects. It will basically put _all_ GPIO IRQs on
the same CPU which may slow down other peripherals, like UART, with potential
of buffer overrun (on the high speed modes).

Ideally it should be done in a way that exact consumer may ask for this from
its driver. Yet, I have no idea how to achieve this, but it would be really
nice to have something in I²C HID to

	set_the_same_affinity_as_parent/GPIO_irq()

..

> Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Cc: Hans de Goede <hdegoede@...hat.com>

You can move these (Cc lines) to be after ---, that they won't pollute
the commit message with the same effect made on email, i.e. Cc'ing to
the listed people.

-- 
With Best Regards,
Andy Shevchenko