linux-kernel - Re: [PATCH 3/3] ACPI: EC: Change EC noirq tuning to be an optional behavior

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Message-ID: <1792284.us4mECpxNF@aspire.rjw.lan>
Date:   Wed, 28 Jun 2017 23:31:16 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Lv Zheng <lv.zheng@...el.com>
Cc:     "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Len Brown <len.brown@...el.com>, Lv Zheng <zetalog@...il.com>,
        linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: Re: [PATCH 3/3] ACPI: EC: Change EC noirq tuning to be an optional behavior

On Wednesday, June 14, 2017 01:59:24 PM Lv Zheng wrote:
> According to the bug report, though the busy polling mode can make noirq
> stages executed faster, it causes abnormal fan blowing in noirq stages.
> 
> This patch prepares an option so that the automatic busy polling mode
> switching for noirq stages can be enabled by who wants to tune it, not all
> users.
> Noticed that the new global option cannot be changed during noirq stages.
> There is no need to lock its value changes to sync with polling mode
> settings switches.
> 
> For reporters and testers in the thread, as there are too many reporters
> on the bug link, this patch only picks names from most active commenters.
> Sorry for the neglet.
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=191181
> Reported-by: Tatsuyuki Ishi <ishitatsuyuki@...il.com>
> Reported-by: Claudio Sacerdoti Coen <claudio.sacerdoticoen@...bo.it>
> Tested-by: Nicolo' <nicolopiazzalunga@...il.com>
> Reported-by: Jens Axboe <axboe@...nel.dk>
> Tested-by: Gjorgji Jankovski <j.gjorgji@...il.com>
> Tested-by: Damjan Georgievski <gdamjan@...il.com>
> Tested-by: Fernando Chaves <nanochaves@...il.com>
> Signed-off-by: Lv Zheng <lv.zheng@...el.com>

First of all, this seems to be a fix for commit c3a696b6e8f8 (ACPI / EC: Use busy polling
mode when GPE is not enabled), so there should be a Fixes: tag pointing to that
one.

Moreover, if that is just a performance optimization and not a matter of correctness,
why don't we simply drop acpi_ec_enter/leave_noirq() entirely?

What is going to break if we do that?

Thanks,
Rafael