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Message-ID: <CAG-rBihBkTeZR6yMSF+5zg-h1U1pxGuN-nv=Y7DXLvxV435hDw@mail.gmail.com>
Date: Tue, 29 Aug 2023 12:35:07 -0400
From: Sven van Ashbrook <svenva@...omium.org>
To: Ben Chuang <benchuanggli@...il.com>,
"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Cc: skardach@...gle.com, adrian.hunter@...el.com,
SeanHY.chen@...esyslogic.com.tw, ben.chuang@...esyslogic.com.tw,
greg.tu@...esyslogic.com.tw, jason.lai@...esyslogic.com.tw,
jasonlai.genesyslogic@...il.com, linux-kernel@...r.kernel.org,
linux-mmc@...r.kernel.org, reniuschengl@...il.com,
stable@...r.kernel.org, ulf.hansson@...aro.org,
victor.shih@...esyslogic.com.tw, victorshihgli@...il.com
Subject: Re: [PATCH v2] mmc: sdhci-pci-gli: fix LPM negotiation so x86/S0ix
SoCs can suspend
+ Rafael for advice on runtime_pm corner cases.
On Mon, Aug 28, 2023 at 10:48 PM Ben Chuang <benchuanggli@...il.com> wrote:
>
>
> My concern is that when runtime_pm is false, gl9763e is disabled LPM
> negotiation, gl9763e can't enter L1.x and s0ix may fail.
> It seems that runtime_pm will always exist and that's ok.
>
Thank you. I believe we can address your concern.
- XXX_suspend/XXX_resume (i.e. classic suspend/resume) depends on
CONFIG_PM_SLEEP. This always selects CONFIG_PM. This always includes
the runtime_pm framework. So, if XXX_suspend/XXX_resume gets called,
the runtime_pm framework is always present, but may not be actively
managing the device.
- "when runtime_pm is false" AFAIK the only way to disable runtime_pm
when CONFIG_PM is set, is to write "on" to /sys/devices/.../power/control.
See https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-devices-power
In that case, the runtime_pm framework will activate the device, calling
XXX_runtime_resume() if necessary. Are there other ways of disabling it?
- if /sys/devices/.../power/control is "on", then:
gl9763e_runtime_resume() always called -> LPM always disabled
gl9763e_suspend() -> LPM enabled -> gl9763e_resume() -> LPM disabled
In between "classic" XXX_suspend and XXX_resume, LPM will be enabled,
so the device can enter L1.x and S0ix.
And the LPM negotiation flags look correct.
Does that address your concerns?
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