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

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Message-ID: <20191009165128.GB1595@onstation.org>
Date:   Wed, 9 Oct 2019 12:51:28 -0400
From:   Brian Masney <masneyb@...tation.org>
To:     Stephen Boyd <sboyd@...nel.org>
Cc:     robdclark@...il.com, sean@...rly.run, bjorn.andersson@...aro.org,
        a.hajda@...sung.com, Laurent.pinchart@...asonboard.com,
        airlied@...ux.ie, daniel@...ll.ch, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        freedreno@...ts.freedesktop.org, jonathan@...ek.ca,
        Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH RFC v2 4/5] ARM: dts: qcom: msm8974: add HDMI nodes

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@...22100 {
> > > > +                               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