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:   Sun, 29 Aug 2021 23:53:37 +0200
From:   Marijn Suijten <marijn.suijten@...ainline.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.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

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.

> Other than that this looks good to me.


Any r-b/a-b/t-b I can pick up for the next round?

- Marijn