linux-kernel - Re: [PATCH 2/3] drm/msm/dsi: Use "ref" fw clock instead of global name for VCO parent

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Date:   Mon, 30 Aug 2021 04:17:32 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Marijn Suijten <marijn.suijten@...ainline.org>
Cc:     phone-devel@...r.kernel.org, ~postmarketos/upstreaming@...ts.sr.ht,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Martin Botka <martin.botka@...ainline.org>,
        Jami Kettunen <jami.kettunen@...ainline.org>,
        Pavel Dubrova <pashadubrova@...il.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Abhinav Kumar <abhinavk@...eaurora.org>,
        Jonathan Marek <jonathan@...ek.ca>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <linux-arm-msm@...r.kernel.org>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <dri-devel@...ts.freedesktop.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] drm/msm/dsi: Use "ref" fw clock instead of global
 name for VCO parent

On Mon, 30 Aug 2021 at 00:53, Marijn Suijten
<marijn.suijten@...ainline.org> wrote:
>
> Hi Dmitry,
>
> On 8/29/21 10:39 PM, Dmitry Baryshkov wrote:
> > Hi,
> >
> > On Sun, 29 Aug 2021 at 23:30, Marijn Suijten
> > <marijn.suijten@...ainline.org> wrote:
> >>
> >> All DSI PHY/PLL drivers were referencing their VCO parent clock by a
> >> global name, most of which don't exist or have been renamed.  These
> >> clock drivers seem to function fine without that except the 14nm driver
> >> for the sdm6xx [1].
> >>
> >> At the same time all DTs provide a "ref" clock as per the requirements
> >> of dsi-phy-common.yaml, but the clock is never used.  This patchset puts
> >> that clock to use without relying on a global clock name, so that all
> >> dependencies are explicitly defined in DT (the firmware) in the end.
> >
> > msm8974 (28nm-hpm) does not define the "ref" clock. So you'd have to:
> > 1) add ref clock to the dtsi (should come in a separate patch).
>
>
> Thanks for double-checking and noticing this!  I've queued up this patch
> for v2.
>
> > 2) add .name = "xo" as a fallback to the 28nm driver (to be compatible
> > with older devices)
>
>
> Are there msm8974 devices out there that might upgrade kernels, but not
> firmware (DT)?  On other boards (sdm630) I'm removing these from various
> drivers as to not have any possibility of relying on global names, in
> favour of having the clock dependencies fully specified in the DT.

IIUC it is a general policy of trying to be (somewhat)
backwards-compatible. For example because your dts might come from a
different source/be a part of different build process/etc.

>
> > Other than that this looks good to me.
>
>
> Any r-b/a-b/t-b I can pick up for the next round?

Let's get those issues fixed and I'll respond with R-B tags


-- 
With best wishes
Dmitry