linux-kernel - Re: [PATCH v1] chrome/cros_ec: Handle events during suspend after resume completion

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Message-ID: <ZisvhAg5Jy_IE-AV@google.com>
Date: Fri, 26 Apr 2024 12:37:24 +0800
From: Tzung-Bi Shih <tzungbi@...nel.org>
To: Karthikeyan Ramasubramanian <kramasub@...omium.org>
Cc: LKML <linux-kernel@...r.kernel.org>, stable@...r.kernel.org,
	Lalith Rajendran <lalithkraj@...omium.org>,
	chrome-platform@...ts.linux.dev, Benson Leung <bleung@...omium.org>,
	Guenter Roeck <groeck@...omium.org>
Subject: Re: [PATCH v1] chrome/cros_ec: Handle events during suspend after
 resume completion

On Thu, Apr 25, 2024 at 02:37:11PM -0600, Karthikeyan Ramasubramanian wrote:
> On boards where EC IRQ is not wake capable, EC does not trigger IRQ to
> signal any non-wake events until EC receives host resume event.

The sentence looks irrelevant to the fix.  Presumably, EC should send those
pending non-wake events after it receives host resume event.

> Commit 47ea0ddb1f56 ("platform/chrome: cros_ec_lpc: Separate host
> command and irq disable") separated enabling IRQ and sending resume
> event host command into early_resume and resume_complete stages
> respectively. This separation leads to host not handling certain events
> posted during a small time window between early_resume and
> resume_complete stages. This change moves handling all events that
> happened during suspend after sending host resume event.

The regression you see is probably not due to the "separation" but an unwanted
code reorder.

Before 47ea0ddb1f56[1], a resume is:
1) Enable IRQ.
2) Send resume event.
3) Handle pending events.

After 47ea0ddb1f56[2], a resume is:
1) Enable IRQ.
2) Handle pending events.
3) Send resume event.

If there are some more events pending between 2) and 3), they would be handled
further late.

[1]: https://elixir.bootlin.com/linux/v6.6/source/drivers/platform/chrome/cros_ec.c#L381
[2]: https://elixir.bootlin.com/linux/v6.7/source/drivers/platform/chrome/cros_ec.c#L438

I see what the patch tries to fix but the commit message makes less sense to
me.  Please fix accordingly.