linux-kernel - Re: [PATCH RFC 1/3] drm/msm/adreno: Add support for ACD

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Message-ID: <20241021220914.vrxiyeoxjyxweovu@hu-akhilpo-hyd.qualcomm.com>
Date: Tue, 22 Oct 2024 03:39:14 +0530
From: Akhil P Oommen <quic_akhilpo@...cinc.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
CC: Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        "Konrad
 Dybcio" <konradybcio@...nel.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Marijn Suijten
	<marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, "Simona
 Vetter" <simona@...ll.ch>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon
	<nm@...com>,
        Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        <linux-arm-msm@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        <linux-pm@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: Re: [PATCH RFC 1/3] drm/msm/adreno: Add support for ACD

On Mon, Oct 21, 2024 at 11:38:41AM +0200, Konrad Dybcio wrote:
> On 11.10.2024 10:29 PM, Akhil P Oommen wrote:
> > ACD a.k.a Adaptive Clock Distribution is a feature which helps to reduce
> > the power consumption. In some chipsets, it is also a requirement to
> > support higher GPU frequencies. This patch adds support for GPU ACD by
> > sending necessary data to GMU and AOSS. The feature support for the
> > chipset is detected based on devicetree data.
> > 
> > Signed-off-by: Akhil P Oommen <quic_akhilpo@...cinc.com>
> > ---
> 
> [...]
> 
> > +
> > +	/* Initialize qmp node to talk to AOSS */
> > +	gmu->qmp = qmp_get(gmu->dev);
> > +	if (IS_ERR(gmu->qmp)) {
> > +		cmd->enable_by_level = 0;
> > +		return dev_err_probe(gmu->dev, PTR_ERR(gmu->qmp), "Failed to initialize qmp\n");
> > +	}
> 
> I'm still in favor of keeping qmp_get where it currently is, so that
> probe can fail/defer faster

Sorry, I somehow missed this email from you until now.

If it fails, then it probably doesn't matter if it is a bit late. But for defer, isn't there
some optimizations to track the dependency from devicetree data? I am
not entirely sure!

Since qmp node is related to ACD, I felt it is better to:
  1. Keep all acd probe related code in a single place.
  2. Be more opportunistic in skipping qmp_get() wherever possible.

But if you still have strong opinion on this, I can move it back in the
next revision (v3).

-Akhil

> 
> Konrad