linux-kernel - Re: [PATCH v4 07/13] i2c: acpi: Use ACPI wake capability bit to set wake

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Date:   Tue, 20 Sep 2022 15:32:13 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Raul E Rangel <rrangel@...omium.org>
Cc:     linux-acpi@...r.kernel.org, linux-input@...r.kernel.org,
        timvp@...gle.com, hdegoede@...hat.com, rafael@...nel.org,
        mario.limonciello@....com, jingle.wu@....com.tw,
        mika.westerberg@...ux.intel.com, dmitry.torokhov@...il.com,
        linus.walleij@...aro.org, Wolfram Sang <wsa@...nel.org>,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 07/13] i2c: acpi: Use ACPI wake capability bit to set
 wake_irq

On Mon, Sep 19, 2022 at 09:59:09AM -0600, Raul E Rangel wrote:
> Device tree already has a mechanism to pass the wake_irq. It does this
> by looking for the wakeup-source property and setting the
> I2C_CLIENT_WAKE flag. This CL adds the ACPI equivalent. It uses the
> ACPI interrupt wake flag to determine if the interrupt can be used to
> wake the system. Previously the i2c drivers had to make assumptions and
> blindly enable the wake IRQ. This can cause spurious wake events. e.g.,
> If there is a device with an Active Low interrupt and the device gets
> powered off while suspending, the interrupt line will go low since it's
> no longer powered and wakes the system. For this reason we should
> respect the board designers wishes and honor the wake bit defined on the
> interrupt.

...

> +	if (irq_ctx.irq == -ENOENT)
> +		irq_ctx.irq = acpi_dev_gpio_irq_wake_get(adev, 0, &irq_ctx.wake_capable);

I just realized, that there is an inconsistency on how we fill the wake_capable
parameter. In some cases we check for IRQ for an error condition (IRQ not found)
and in some the wake_capable still be filled.

Here the best approach I believe is to add

	if (irq_ctx.irq < 0)
		return irq_ctx.irq;

I.o.w. we apply the rule "do not fill the output parameters when it's known
to be an error condition".

> +	if (wake_capable)
> +		*wake_capable = irq_ctx.wake_capable;

> +	return irq_ctx.irq;

-- 
With Best Regards,
Andy Shevchenko