[alsa-devel] [PATCH 1/2] ASoC: sgtl5000: Simplify the handling of VDDD

[Fabio Estevam]

On 05/13/2013 01:41 PM, Matt Sealey wrote:
> Nack.
>
> While I like the concept, I don't like the following:
>
> * That the regulator-before-read-chip-id should be a separate patch (please)
I thought about doing like this initially and that would require some 
heavy cleanup.
> * That this revision check went away without anyone fully knowing WHY
> it was there in the first place
> * I am fairly certain the first run consumer-purchased Efika MX boards
> have an older SGTL5000 on them and I would like to know if the
> internal LDO actually operates on those.. and don't want to churn by
> reintroducing such a patch.
Can you test on this platform, please?

>
> As far as I see the operation after patch would be that VDDD is
> accepted in the DT, enabled, and then LDO is enabled (thus shunting
> VDDD-LDO supply to the highest of VDDA or VDDIO, or VDDA in the case
> VDDA&VDDIO >3.1V) which leaves the board VDDD enabled until the driver
> is removed.
How does this differ from current code?
>
> If you're enabling the LDO, please disable board VDDD.
Agree, but that would be another patch.

> And please
> consider that on Efika MX and Babbage, VDDD is supplied at 1.2V by a
> separate on-board regulator, so using VDDIO->LDO->1.2V is completely
> obtuse and doubles codec power consumption.
Babbage leaves VDDD unconnected.

>
> I am leaning towards the case that the revision check is redundant, in
> that since there is no design data that says the LDO was
> non-operational or has any differences between versions the only
> difference is in the particulars of the implementation on the board
> itself. It seems like it is coded as a non-intrusive hack on the
> assumption that "any board with SGTL5000 0x11 is a production
> Freescale reference platform which does not supply VDDD" rather than
> having to go and re-validate a ridiculous number of supported
> reference designs. Unless I see data otherwise..
Yes, I also do not find any data for this revision check.

>
> If that's true, what we need here is to keep VDDD if it's supplied,
> and remove VDDD from the DT where it is not, and optionally tell the
> codec to force usage of the internal LDO in the case of supplied VDDD
> (i.e. please disable VDDD), and WHICH source to use for the charge
> pump (VDDIO or VDDA) in case the automated default setting is not
> desirable..
Yes, but this would also need to be another patch.