Re: [PATCH 2/2] mmc: sunxi: Also set SDXC_LOW_POWER_ON

[Hans de Goede]

Hi,

On 28-05-15 10:02, Ulf Hansson wrote:
> On 25 May 2015 at 09:02, Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
> > Hi,
> >
> > On 24-05-15 20:04, Michal Suchanek wrote:
> > > The function sunxi_mmc_oclk_onoff filters out the SDXC_LOW_POWER_ON flag
> > > but never sets it.
> > >
> > > Set SDXC_LOW_POWER_ON when oclk is disabled.
> >
> >
> > Nack, looking at the datasheet I do not thing this patch actually
> > does anything, according to the datasheet setting this bit to 1 results
> > in: "Turn off card clock when FSM in IDLE state", iow this does mmc clock
> > gating on idle automatically in hardware, since we completely disable the
> > clock on clock-off by clearing SDXC_CARD_CLOCK_ON setting this bit on
> > clock-off is a nop.
> >
> > We could consider actually setting this to safe power when setting the clock
> > on, for doing that it would be good to look at the android code and see if
> > it ever sets this bit and if so when.
> >
> > WRT CONFIG_MMC_CLKGATE we are probably better off using SDXC_LOW_POWER_ON
> > then that when it is enabled. So maybe we should set SDXC_LOW_POWER_ON
> > based on #ifdef WRT CONFIG_MMC_CLKGATE, and have some way to tell the
> > mmc core to not do clock gating on this host ?
>
> I am planning to remove the entire thing for CONFIG_MMC_CLKGATE, maybe
> it's time to do that now!?

Removing it now sounds like a good plan to me, we would still need
to look into maybe enabling SDXC_LOW_POWER_ON on sunxi in some cases
to save power, but that is an orthogonal problem.

Regards,

Hans
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