Re: [PATCH 1/2] drm/bridge: sii902x: Enable I/O and core VCC supplies if present

[Alex G.]

On 9/26/20 1:49 PM, Sam Ravnborg wrote:
> Hi Alexandru
>
> On Thu, Sep 24, 2020 at 03:05:05PM -0500, Alexandru Gagniuc wrote:
> > On the SII9022, the IOVCC and CVCC12 supplies must reach the correct
> > voltage before the reset sequence is initiated. On most boards, this
> > assumption is true at boot-up, so initialization succeeds.
> >
> > However, when we try to initialize the chip with incorrect supply
> > voltages, it will not respond to I2C requests. sii902x_probe() fails
> > with -ENXIO.
> >
> > To resolve this, look for the "iovcc" and "cvcc12" regulators, and
> > make sure they are enabled before starting the reset sequence. If
> > these supplies are not available in devicetree, then they will default
> > to dummy-regulator. In that case everything will work like before.
> >
> > This was observed on a STM32MP157C-DK2 booting in u-boot falcon mode.
> > On this board, the supplies would be set by the second stage
> > bootloader, which does not run in falcon mode.
> >
> > Signed-off-by: Alexandru Gagniuc <mr.nuke.me@xxxxxxxxx>
>
> One nitpick here. The binding should be present in the tree before
> you start using it. So this patch should be applied after the binding.

It is :)
  * arch/arm/boot/dts/stm32mp15xx-dkx.dtsi

Alex

> One detail below - I think others have already commented on the rest.
[snip]