linux-kernel - RE: [PATCH 1/2] dt-bindings: msm/dp: List supplies in the bindings

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Date:   Thu, 5 May 2022 14:18:14 -0400
From:   Stephen Boyd <swboyd@...omium.org>
To:     Doug Anderson <dianders@...omium.org>,
        Sankeerth Billakanti <sbillaka@....qualcomm.com>
Cc:     "bjorn.andersson@...aro.org" <bjorn.andersson@...aro.org>,
        "dmitry.baryshkov@...aro.org" <dmitry.baryshkov@...aro.org>,
        Rob Clark <robdclark@...omium.org>,
        Rob Herring <robh+dt@...nel.org>,
        Vinod Koul <vkoul@...nel.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        "linux-phy@...ts.infradead.org" <linux-phy@...ts.infradead.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        Sankeerth Billakanti <quic_sbillaka@...cinc.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Kalyan Thota <quic_kalyant@...cinc.com>,
        Kuogee Hsieh <quic_khsieh@...cinc.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        devicetree@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/2] dt-bindings: msm/dp: List supplies in the bindings

Quoting Sankeerth Billakanti (2022-05-05 11:02:36)
> >>
> >> Quoting Douglas Anderson (2022-04-25 14:06:42)
> >>
> >> Having 'a' in 'vdda' typically means 'analog' for 'analog' circuits,
> >> so I'd expect this to only matter for the phy that contains the analog
> >> circuitry. It would be great to remove the regulator code from
> >> drivers/gpu/drm/msm/dp/dp_power.c and move the regulator_set_load()
> >> call to the phy driver if possible. Hopefully qcom folks can help
> >> clarify here.
> >
> >Interesting. Oddly enough, the sc7280 datasheet doesn't list the "_A".
> >It calls these "VDD_VREF_0P9" and "VDD_VREF_1P2". However, on the
> >schematic in front of me someone labeled these pins on the sc7280 with the
> >"A". ...and the driver looks for a supply with the "a". :-/
> >
> >It would be good to get clarification from someone with better information.
> >
> >-Doug
>
> Our internal power grid documents list the regulators as VDD_A_*_1P2 and VDD_A_*_0P9
> for all the platforms.

Do your internal power grid documents indicate what these supplies are
powering? The question is if these supplies power any of the logic
inside the eDP controller or if they only supply power to the analog
circuits in the eDP phy. If it's the eDP phy only then the regulator
usage in the eDP driver should be removed. I would suspect this is the
case because the controller is probably all digital logic and runs at
the typical 1.8V that the rest of the SoC uses. Similarly, these are
voltage references which sound like a PLL reference voltage.

Please clarify this further.

>
> So, as a practice, we put the same name in the DT files. Hence,
>
> Reviewed-by: Sankeerth Billakanti <quic_sbillaka@...cinc.com>
>