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

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Date:   Mon, 3 Jul 2017 05:15:26 +0000
From:   "Zheng, Lv" <lv.zheng@...el.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        "Chen, Yu C" <yu.c.chen@...el.com>
CC:     "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "Brown, Len" <len.brown@...el.com>, Lv Zheng <zetalog@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>
Subject: RE: [PATCH 3/3] ACPI: EC: Change EC noirq tuning to be an optional
 behavior

Hi, Rafael

> From: Rafael J. Wysocki [mailto:rjw@...ysocki.net]
> 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?

Let me Cc Yu for justification.
I just added busy poll support for suspend/boot according to the root cause reported by him.
He should know the end user requirements better than me.

Thanks and best regards
Lv