Re: [PATCH] mmc: rtsx: add card power off during probe

[Adrian Hunter]

On 23/09/2014 12:20 p.m., Ulf Hansson wrote:
> On 22 September 2014 12:09, Roger Tseng <rogerable@xxxxxxxxxxx> wrote:
> > On Thu, 2014-09-18 at 23:14 +0200, Ulf Hansson wrote:
> > > [...]
> > >
> > > > > In that case, don't forget to enable MMC_CAP2_FULL_PWR_CYCLE.
> > > > >
> > > > > > if MMC_CAP2_NO_PRESCAN_POWERUP enable, will call mmc_power_off() at start,
> > > > > > then it will check ios.power_mode, but the state is MMC_POWER_OFF and just
> > > > > > return.
> > > > >
> > > > > Uhh, that's right! So, I wonder why we invokes mmc_power_off() from
> > > > > that path at all.
> > > > >
> > > > > Hmm, I think we should change the behavior in mmc_start_host(), like below:
> > > > > 1) Add a "MMC_POWER_UNDEFINED" state which is what the power state
> > > > > should be assigned to at allocation.
> > > > > 2 ) From mmc_start_host(), invoke mmc_power_off() when
> > > > > MMC_CAP2_NO_PRESCAN_POWERUP and MMC_CAP2_FULL_PWR_CYCLE is set.
> > > > >
> > > > > Would that work?
> > > > Yes. I have confirmed this by following changes. The MMC_POWER_UNDEFINED
> > > > designation in mmc_start_host() will eventually cause a power-off
> > > > operation.
> > > >
> > > > But I wonder if we need to additionally check MMC_CAP2_FULL_PWR_CYCLE
> > > > before calling mmc_power_off()?
> > >
> > > The intent from my side was to keep the current behaviour for those
> > > that already used MMC_CAP2_NO_PRESCAN_POWERUP, but it's s not a big
> > > deal.
> >
> > I checked the log and found the commit that invokes mmc_power_off():
> > a08b17be8b984a7c51cd5a480cd977363df353f9
> > 0d3e3350d5871c53464be4c92d57198744247005
> > (https://www.mail-archive.com/linux-mmc@xxxxxxxxxxxxxxx/msg19638.html )
> >
> > The proposed change might bring back some delay since invoking
> > mmc_power_off() in mmc_start_host() is more than NOP now and triggers
> > real power-off and re-init in sdhci.
>
> Actually the above commits was added due to the below commit:
>
> fa5501890d8974301042e0202d342a6cbe8609f4
>
> But the commits you refer to, didn't bring back the old behaviour,
> which I think was the intent. Instead we added a NOP call to
> mmc_power_off() from mmc_start_host().
>
> We have few options on how to go forward, but let's loop in Adrian
> Hunter first, since he might be able to comment on this as well.

Having mmc_power_off() in mmc_start_host()
actually power off should be OK.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/