Re: [PATCH v3 2/7] regulator: qca6390: add support for QCA639x powerup sequence

[Ulf Hansson]

- Peter (the email was bouncing)

On Tue, 6 Jul 2021 at 13:55, Mark Brown <broonie@xxxxxxxxxx> wrote:
>
> On Tue, Jul 06, 2021 at 09:54:03AM +0200, Ulf Hansson wrote:
> > On Tue, 22 Jun 2021 at 00:32, Dmitry Baryshkov
>
> > > Qualcomm QCA6390/1 is a family of WiFi + Bluetooth SoCs, with BT part
> > > being controlled through the UART and WiFi being present on PCIe
> > > bus. Both blocks share common power sources. Add device driver handling
> > > power sequencing of QCA6390/1.
>
> > Power sequencing of discoverable buses have been discussed several
> > times before at LKML. The last attempt [1] I am aware of, was in 2017
> > from Peter Chen. I don't think there is a common solution, yet.
>
> This feels a bit different to the power sequencing problem - it's not
> exposing the individual inputs to the device but rather is a block that
> manages everything but needs a bit of a kick to get things going (I'd
> guess that with ACPI it'd be triggered via AML).  It's in the same space
> but it's not quite the same issue I think, something that can handle
> control of the individual resources might still struggle with this.

Well, to me it looks very similar to those resouses we could manage
with the mmc pwrseq, for SDIO. It's also typically the same kind of
combo-chips that moved from supporting SDIO to PCIe, for improved
performance I guess. More importantly, the same constraint to
pre-power on the device is needed to allow it to be discovered/probed.

Therefore, I think it would be worth having a common solution for
this, rather than a solution per subsystem or even worse, per device.

Unfortunately, it looks like Peter's email is bouncing so we can't get
an update from him.

Kind regards
Uffe