Hi Ulf,
> From: Ulf Hansson, Sent: Monday, June 8, 2020 11:51 PM
>
> On Mon, 8 Jun 2020 at 14:36, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:
> >
> > Hi Ulf,
> >
> > On Mon, Jun 8, 2020 at 1:47 PM Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
> > > On Mon, 8 Jun 2020 at 12:39, Yoshihiro Shimoda
> > > <yoshihiro.shimoda.uh@xxxxxxxxxxx> wrote:
> > > > > From: Ulf Hansson, Sent: Monday, June 8, 2020 5:14 PM
> > > > > On Thu, 4 Jun 2020 at 14:17, Yoshihiro Shimoda
> > > > > <yoshihiro.shimoda.uh@xxxxxxxxxxx> wrote:
> > > > > > > From: Yoshihiro Shimoda, Sent: Tuesday, May 19, 2020 8:33 PM
> > > > > > >
> > > > > > > The commit 432356793415 ("mmc: core: Enable power_off_notify for
> > > > > > > eMMC shutdown sequence") enabled the power off notification
> > > > > > > even if MMC_CAP2_POWEROFF_NOTIFY (MMC_CAP2_FULL_PWR_CYCLE now) is
> > > > > > > not set. However, the mmc core lacks to issue the power off
> > > > > > > notificaiton when Suspend-to-{RAM,Disk} happens on the system.
> > > > > > >
> > > > > > > So, add Suspend-to-RAM support at first because this is easy to
> > > > > > > check by using pm_suspend_target_state condition on _mmc_suspend().
> > > > > > >
> > > > > > > Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
> > > > > >
> > > > > > I'd like to add more detail why this patch is needed.
> > > > > > I think we should think some events (which are Shutdown, Suspend-to-idle,
> > > > > > Suspend-to-RAM) for the Power off Notification control.
> > > > > > I described these events like below.
> > > > > >
> > > > > > Assumption of the host : MMC_CAP2_FULL_PWR_CYCLE=false
> > > > > > Assumption of the eMMC : in POWERED_ON
> > > > > >
> > > > > > 1) Event : Shutdown
> > > > > > - power : going to VCC=OFF & VCCQ=OFF
> > > > > > - ideal : Either POWER_OFF_LONG or POWER_OFF_SHORT
> > > > > > - current : POWER_OFF_LONG --> Perfect
> > > > > > - Remarks : the commit 432356793415
> > > > > >
> > > > > > 2) Event : Suspend-to-Idle
> > > > > > - power : Keep VCC=ON & VCCQ=ON
> > > > > > - ideal : issue MMC_SLEEP_AWAKE and keep the power (because the host could not change VCC=OFF)
> > > > > > - current : issue MMC_SLEEP_AWAKE and keep the power --> Perfect
> > > > > > - Remarks : IIUC, even if the eMMC is in POWERED_ON, a host can issue CMD5 (sleep).
> > > > >
> > > > > As a matter of fact, VCCQ *must* remain on in sleep state, while VCC
> > > > > can be powered off.
> > > >
> > > > I got it.
> > > >
> > > > > >
> > > > > > 3) Event : Suspend-to-RAM
> > > > > > - power : going to VCC=OFF & VCCQ=OFF
> > > > >
> > > > > I don't understand why you think S2R should be treated differently
> > > > > from S2I? At least from the MMC subsystem point of view, there is no
> > > > > difference. No?
> > > >
> > > > On my environment, VCC & VCCQ condition differs like below.
> > > > S2I: VCC=ON & VCCQ=ON
> > > > S2R: VCC=OFF & VCCQ=OFF
> > >
> > > Can you explain why it differs? Who is managing the regulators and who
> > > decides to turn them off?
> >
> > The firmware does, through PSCI system suspend.
> > And what it does exactly is not standardized.
>
> This sounds really weird. Especially, to let PSCI handle the VCC
> regulator seems wrong, while PSCI is about power for CPUs and CPU
> clusters (and corresponding power rails).
>
> Oh well, nevermind.
>
> > Perhaps we do need an "arm,psci-system-suspend-is-power-down"[1]
> > DT property?
>
> Hmm.
>
> I wouldn't limit this to PSCI, but rather see this as a generic FW issue.
>
> In principle, it sounds to me, like we need to dynamically allow the
> mmc host to update MMC_CAP2_FULL_PWR_CYCLE, depending on what system
> suspend mode we are about to enter. Or something along those lines.
I see.
However, I have no idea how to inform to a host about the FW will turn
the power off in suspend mode for now...
By the way, this is a workaround though, to avoid the issue (entering
sleep mode and power off), could we add a new property to a mmc host?
Best regards,
Yoshihiro Shimoda
> >
> > > Perhaps this is a regulator-enable usage count problem?
> >
> > Unfortunately not. Else we could fix it :-)
>
> I see.
>
> [...]
>
> Kind regards
> Uffe
