linux-kernel - Re: [PATCH v2] arm64/dts/qcom/sc7180: Add Display Port dt node

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Message-ID: <YL6sY/1E5wLzMiP/@yoga>
Date:   Mon, 7 Jun 2021 18:31:47 -0500
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     khsieh@...eaurora.org, swboyd@...omium.org
Cc:     robdclark@...il.com, sean@...rly.run, vkoul@...nel.org,
        agross@...nel.org, robh+dt@...nel.org, devicetree@...r.kernel.org,
        abhinavk@...eaurora.org, aravindh@...eaurora.org,
        freedreno@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] arm64/dts/qcom/sc7180: Add Display Port dt node

On Mon 07 Jun 12:48 CDT 2021, khsieh@...eaurora.org wrote:

> On 2021-06-05 22:07, Bjorn Andersson wrote:
> > On Thu 03 Jun 16:56 CDT 2021, khsieh@...eaurora.org wrote:
> > 
> > > On 2021-06-03 09:53, Bjorn Andersson wrote:
> > > > On Thu 03 Jun 11:09 CDT 2021, Kuogee Hsieh wrote:
> > [..]
> > > > > diff --git a/arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi
> > [..]
> > > > > +				power-domains = <&rpmhpd SC7180_CX>;
> > > >
> > > > Just curious, but isn't the DP block in the MDSS_GDCS? Or do we need to
> > > > mention CX here in order for the opp framework to apply required-opps
> > > > of CX?
> > > 
> > > yes,
> > 
> > If you want me, or other maintainers, to spend any time reviewing or
> > applying your patches going forward then you need to actually bother
> > replying properly to the questions asked.
> > 
> > Thanks,
> > Bjorn
> 
> Sorry about the confusion. What I meant is that even though DP controller is
> in the MDSS_GDSC
> power domain, DP PHY/PLL sources out of CX. The DP link clocks have a direct
> impact
> on the CX voltage corners. Therefore, we need to mention the CX power domain
> here. And, since
> we can associate only one OPP table with one device, we picked the DP link
> clock over other
> clocks.

Thank you, that's a much more useful answer.

Naturally I would think it would make more sense for the PHY/PLL driver
to ensure that CX is appropriately voted for then, but I think that
would result in it being the clock driver performing such vote and I'm
unsure how the opp table for that would look.

@Stephen, what do you say?

Regards,
Bjorn