linux-kernel - Re: [PATCH v16 0/3] eDP/DP Phy vdda realted function

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Date:   Thu, 21 Jul 2022 12:20:23 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Johan Hovold <johan@...nel.org>
Cc:     Kuogee Hsieh <quic_khsieh@...cinc.com>,
        Douglas Anderson <dianders@...omium.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Vinod Koul <vkoul@...nel.org>, dri-devel@...ts.freedesktop.org,
        robdclark@...il.com, sean@...rly.run, swboyd@...omium.org,
        daniel@...ll.ch, airlied@...ux.ie, agross@...nel.org,
        dmitry.baryshkov@...aro.org, quic_abhinavk@...cinc.com,
        quic_aravindh@...cinc.com, quic_sbillaka@...cinc.com,
        freedreno@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Liam Girdwood <lgirdwood@...il.com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Subject: Re: [PATCH v16 0/3] eDP/DP Phy vdda realted function

On Thu, Jul 21, 2022 at 12:31:41PM +0200, Johan Hovold wrote:

If you're copying someone into a thread that's not obviously relevant
for them it's good practice to put a note about it at the top of the
mail to reduce the chances that it just gets deleted unread - people get
copies of all sorts of random stuff for not great reasons (like getting
pulled in by checkpatch due to once having done a cleanup) and are often
quicky to delete things.

> This series breaks USB and PCIe for some SC8280XP and SA540P machines
> where the DP PHY regulators are shared with other PHYs whose drivers do
> not request a load.

> Specifically, the hard-coded vdda-phy load of 21.8 mA added by this
> series, causes several RPMh regulators to now be put in low-power mode.

> I found Doug's suggestion to handle situations like this in regulator
> core:
> 
> 	https://lore.kernel.org/all/20180814170617.100087-1-dianders@chromium.org/

> but since that was rejected, how do we deal with this generally?

> In the above thread Doug mentioned adding support for load requests to
> further drivers and Bjorn mentioned working around it by adding
> regulator-system-load properties to DT.

> It seems quite likely that changes like this one affects other systems
> too, and the effects may be hard to debug. So a more general solution
> than playing whack-a-mole using DT would be good to have.

You could add a way to specify constant base loads in DT on either a per
regulator or per consumer basis.

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