Re: [PATCH RFC v2 4/5] ARM: dts: qcom: msm8974: add HDMI nodes

Brian Masney
2019-10-09T16:51:32Z

On Wed, Oct 09, 2019 at 08:39:26AM -0700, Stephen Boyd wrote:
> Quoting Brian Masney (2019-10-08 23:05:20)
> > On Tue, Oct 08, 2019 at 07:21:30PM -0700, Stephen Boyd wrote:
> > > Quoting Brian Masney (2019-10-06 18:45:08)
> > > > diff --git a/arch/arm/boot/dts/qcom-msm8974.dtsi b/arch/arm/boot/dts/qcom-msm8974.dtsi
> > > > index 7fc23e422cc5..af02eace14e2 100644
> > > > --- a/arch/arm/boot/dts/qcom-msm8974.dtsi
> > > > +++ b/arch/arm/boot/dts/qcom-msm8974.dtsi
> > > > @@ -1335,6 +1342,77 @@
> > > > clocks = <&mmcc MDSS_AHB_CLK>;
> > > > clock-names = "iface";
> > > > };
> > > > +
> > > > + hdmi: hdmi-tx@fd922100 {
> > > > + status = "disabled";
> > > > +
> > > > + compatible = "qcom,hdmi-tx-8974";
> > > > + reg = <0xfd922100 0x35c>,
> > > > + <0xfc4b8000 0x60f0>;
> > > > + reg-names = "core_physical",
> > > > + "qfprom_physical";
> > >
> > > Is this the qfprom "uncorrected" physical address? If so, why can't this
> > > node use an nvmem to read whatever it needs out of the qfprom?
> >
> > The MSM HDMI code is configured to look for this reg-name here:
> >
> > https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/msm/hdmi/hdmi.c#L582
> >
> > There is a qcom,qfprom configured for this board in DTS, however its at
> > a different address range, so maybe there are multiple qfproms?
> >
> > https://elixir.bootlin.com/linux/latest/source/arch/arm/boot/dts/qcom-msm8974.dtsi#L424
> >
> > msm8996.dtsi has the same style of configuration:
> >
> > https://elixir.bootlin.com/linux/latest/source/arch/arm64/boot/dts/qcom/msm8996.dtsi#L956
> > https://elixir.bootlin.com/linux/latest/source/arch/arm64/boot/dts/qcom/msm8996.dtsi#L1736
> >
>
> There's only one qfprom and there's the address space that's
> "uncorrected" which is not supposed to be used and there's the space
> that is "corrected" and is supposed to be used. It looks like this is
> poking the uncorrected space and it should probably stop doing that and
> use the nvmem provider instead. Maybe someone with docs for this chip
> and 8996 can help confirm this.

Do you know of any publicly-available documentation that describes the
"uncorrected" and "corrected" addresses? I got that qfprom address for
the HDMI from here:

https://github.com/AICP/kernel_lge_hammerhead/blob/n7.1/arch/arm/boot/dts/msm8974-mdss.dtsi#L101

I assume the downstream kernel probably doesn't have the corrected
address anywhere else?

Brian