Re: [PATCH 2/2] mmc: sdhci-iproc: Add support for the legacy sdhci controller on the BCM7211

[Florian Fainelli <f.fainelli@gmail.com>]

On 6/8/2021 5:40 AM, Ulf Hansson wrote:
> On Wed, 2 Jun 2021 at 21:28, Al Cooper <alcooperx@gmail.com> wrote:
>>
>> Add support for the legacy Arasan sdhci controller on the BCM7211 and
>> related SoC's. This includes adding a .shutdown callback to increase
>> the power savings during S5.
> 
> Please split this into two separate changes.
> 
> May I also ask about the ->shutdown() callback and in relation to S5.
> What makes the ->shutdown callback only being invoked for S5?

It is not only called for S5 (entered via poweroff on a prompt) but also
during kexec or reboot. The poweroff path is via:

kernel_power_off() -> kernel_shutdown_prepare() -> device_shutdown() ->
.shutdown()

For kexec or reboot we do not really care about power savings since we
are about to load a new image anyway, however for S5/poweroff we do care
about quiescing the eMMC controller in a way that its clocks and the
eMMC device can be put into low power mode since we will stay in that
mode for seconds/hours/days until someone presses a button on their
remote (or other wake-up sources).
-- 
Florian