RE: [PATCH] mmc: sleep notification

Alex Lemberg
2015-03-10T18:01:42Z

> -----Original Message-----
> From: Ulf Hansson [mailto:ulf.hansson@linaro.org]
> Sent: Tuesday, March 10, 2015 10:22 AM
> To: Alex Lemberg
> Cc: Adrian Hunter; Avi Shchislowski; linux-mmc@vger.kernel.org;
> chris@printf.net
> Subject: Re: [PATCH] mmc: sleep notification
>
> On 10 March 2015 at 17:32, Alex Lemberg <Alex.Lemberg@sandisk.com>
> wrote:
> > Hi Adrian,
> >
> >> -----Original Message-----
> >> From: Adrian Hunter [mailto:adrian.hunter@intel.com]
> >> Sent: Tuesday, March 10, 2015 6:36 AM
> >> To: Avi Shchislowski; ulf.hansson@linaro.org
> >> Cc: linux-mmc@vger.kernel.org; chris@printf.net; Alex Lemberg
> >> Subject: Re: [PATCH] mmc: sleep notification
> >>
> >> On 10/03/15 11:36, Avi Shchislowski wrote:
> >> > This patch is implements the new additional state of
> >> > Power_Off_Notification - SLEEP_NOTIFICATION.
> >> > Until now, the implementation of Power_Off_Notification supported
> >> > only three modes - POWERED_ON (0x01), POWER_OFF_SHORT (0x02) and
> >> > POWER_OFF_LONG (0x03).
> >> >
> >> > As part of eMMC5.0 before moving to Sleep state hosts may set the
> >> > POWER_OFF_NOTIFICATION byte to SLEEP_NOTIFICATION (0x04).
> >> > After setting SLEEP_NOTIFICATION, host should wait for the busy
> >> > line to be de-asserted.
> >> > The max timeout allowed for busy line de-assertion defined in
> >> > SLEEP_NOTIFICATION_TIME byte in EXT_CSD [216].
> >> > HPI may interrupt the SLEEP_NOTIFICATION operation.
> >> > In that case POWER_OFF_NOTIFICATION byte will restore to
> POWERED_ON.
> >>
> >> Is it so that the point of SLEEP_NOTIFICATION is to notify that VCC
> >> will be powered off after the device is put to sleep by CMD5?
> >
> > From the spec:
> >
> > the host should issue a power off notification (POWER_OFF_LONG,
> > POWER_OFF_SHORT ) if it intends to turn off both VCC and VCCQ power
> > supplies or it may use to a power off notification (SLEEP_NOTIFICATION
> > ) if it intends to turn-off VCC after moving the device to Sleep state.
>
> Ah, so CMD5 will still need to be issued. Thanks for clarifying.
>
> >
> >>
> >> At the moment, the card does not get put to sleep if there is support
> >> for power- off-notification?
> >
> > Driver will send Sleep only if PON is not supported...
>
> Nope, that's not entirely correct.
>
> The MMC core requires PON to be supported by the card and the host to have
> MMC_CAP2_FULL_PWR_CYCLE set. Else it will send sleep (CMD5) instead.
>

You are right - it requires both PON and MMC_CAP2_FULL_PWR_CYCLE to be set...
Thanks for mentioning this.

> Kind regards
> Uffe