linux-kernel - Re: [PATCH 5/5] clk: mediatek: Add MediaTek Helio X10 MT6795 clock drivers

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Message-ID: <b65546e1-2d3a-d525-b664-1730dc06994f@collabora.com>
Date:   Tue, 17 May 2022 10:07:52 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Matthias Brugger <matthias.bgg@...il.com>, robh+dt@...nel.org
Cc:     krzysztof.kozlowski+dt@...aro.org, mturquette@...libre.com,
        sboyd@...nel.org, p.zabel@...gutronix.de, y.oudjana@...tonmail.com,
        jason-jh.lin@...iatek.com, ck.hu@...iatek.com,
        fparent@...libre.com, rex-bc.chen@...iatek.com,
        tinghan.shen@...iatek.com, chun-jie.chen@...iatek.com,
        weiyi.lu@...iatek.com, ikjn@...omium.org, miles.chen@...iatek.com,
        sam.shih@...iatek.com, wenst@...omium.org,
        bgolaszewski@...libre.com, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-clk@...r.kernel.org,
        konrad.dybcio@...ainline.org, marijn.suijten@...ainline.org,
        martin.botka@...ainline.org, ~postmarketos/upstreaming@...ts.sr.ht,
        phone-devel@...r.kernel.org, paul.bouchara@...ainline.org,
        kernel@...labora.com
Subject: Re: [PATCH 5/5] clk: mediatek: Add MediaTek Helio X10 MT6795 clock
 drivers

Il 16/05/22 13:30, Matthias Brugger ha scritto:
> 
> 
> On 13/05/2022 18:50, AngeloGioacchino Del Regno wrote:
>> Add the clock drivers for the entire clock tree of MediaTek Helio X10
>> MT6795, including system clocks (apmixedsys, infracfg, pericfg, topckgen)
>> and multimedia clocks (mmsys, mfg, vdecsys, vencsys).
>>
>> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> 
> Thanks a lot for taking care of this!
> I just wonder if we couldn't build most of the clock drivers as modules like done 
> for the mt6779. It would help us to keep the kernel image smaller.
> 

Hello Matthias!

You're welcome!
...but I simply couldn't stand at seeing partially working (..or actually, not
really working) SoCs upstream. If something is upstream, it must work, or it
shouldn't be here for real :-)

Regarding your question about the clock drivers as module... I believe we can,
but that'd be only for {vdec,venc}sys and *maybe* MFG (gpu clocks): I don't know
if it'd be worth to do, as these are about... 8 clocks out of... I haven't counted
them, but more than 250, I think?

It *should* be straightforward though, just about giving them a tristate in Kconfig
instead of a bool, but that would still be limited to just those three...

The reason for me excluding clk-mt6795-mm from this choice is that - at least for
me - my development platform is a commercial smartphone, where the only thing that
"saves you" is having some display output... I mean - I *do* have a UART port, but
that's only because I've been able to solder thin wires on 0.2mm pads... you surely
agree on the fact that this isn't a common practice, even across developers.

Besides, if you think that clk-mt6795-mm should indeed be a module by default,
well, that.. is.. possible - I don't see why it shouldn't be... obviously keeping
in mind that this will largely slow down the boot process, which isn't a big issue.

In any case, it is *not* possible to compile as module *any* of the clock drivers
that I have included in the CONFIG_COMMON_CLK_MT6795 (apmixed, infra, peri, topck)
as.. you know.. these are "a bit critical" on older platforms :-)

How would you proceed?

Cheers,
Angelo