Re: [PATCH v2] mmc: core: Allow specifying current consumption

[Bjorn Andersson <bjorn.andersson@sonymobile.com>]

On Fri 16 Oct 05:55 PDT 2015, Ulf Hansson wrote:

> On 13 October 2015 at 03:00, Bjorn Andersson
> <bjorn.andersson@sonymobile.com> wrote:
> > This allows us to specify expected current consumption of the vmmc and
> > vqmmc regulators. This is needed to bring the supplying regulators out
> > of their low-power-mode while accessing the mmc.
> 
> This indeed makes sense, still I need to think a bit more on this.
> 

Thanks.

We can currently work around this by using "regulator-system-load" on
the vmmc regulator, but a proper fix would be nice.

> For example, can we allow these regulators to enter low power again at
> some times? If so, when and what should that current value be.
> 

The regulator framework recalculates the total load on a regulator upon
enable/disable, but currently it doesn't depend on the state of the
regulator.

I talked to Mark about this a while back and he was positive to us
correcting this, so disabled regulators wouldn't count towards the total
load of a regulator. (So that still is on my todo)


The second option would be to do what is done in the Qualcomm codeaurora
kernels, where the regulators are never disabled and there's a smaller
current specified for the suspend case.

This would require bigger changes to the mmc core I presume, but the
naming of the dt properties support such future adaption.

> Moreover, wouldn't vmmc|vqmmc-active-current be depending what eMMC/SD
> card that is attached?
> 

I would say so, I do however not know how to acquire or encode that
information. Any suggestions here are welcome.

Regards,
Bjorn