linux-kernel - Re: [PATCH v1 35/45] clk: mediatek: Split MT8195 clock drivers and allow module build

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Date:   Thu, 9 Feb 2023 11:46:12 +0800
From:   Chen-Yu Tsai <wenst@...omium.org>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
Cc:     mturquette@...libre.com, sboyd@...nel.org, matthias.bgg@...il.com,
        johnson.wang@...iatek.com, miles.chen@...iatek.com,
        chun-jie.chen@...iatek.com, daniel@...rotopia.org,
        fparent@...libre.com, msp@...libre.com, nfraprado@...labora.com,
        rex-bc.chen@...iatek.com, zhaojh329@...il.com,
        sam.shih@...iatek.com, edward-jw.yang@...iatek.com,
        yangyingliang@...wei.com, granquet@...libre.com,
        pablo.sun@...iatek.com, sean.wang@...iatek.com,
        chen.zhong@...iatek.com, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v1 35/45] clk: mediatek: Split MT8195 clock drivers and
 allow module build

On Wed, Feb 8, 2023 at 5:00 PM AngeloGioacchino Del Regno
<angelogioacchino.delregno@...labora.com> wrote:
>
> Il 08/02/23 09:28, Chen-Yu Tsai ha scritto:
> > On Mon, Feb 6, 2023 at 11:30 PM AngeloGioacchino Del Regno
> > <angelogioacchino.delregno@...labora.com> wrote:
> >>
> >> MT8195 clock drivers were encapsulated in one single (and big) Kconfig
> >> option: there's no reason to do that, as it is totally unnecessary to
> >> build in all or none of them.
> >>
> >> Split them out: keep boot-critical clocks as bool and allow choosing
> >> non critical clocks as tristate.
> >
> > The power domain controller references vppsys*, vdecsys*, vdosys*, wpesys,
> > imgsys and camsys. I'd argue that this makes these clock drivers
> > semi-boot-critical. Maybe mfgcfg as well when we add the GPU?
>
> You don't need to power on additional power domains if you want to load modules
> from a ramdisk! :-)

Right.

> Besides, you caught me: mtk-pm-domains will be my next target after clocks...
> I don't like how it behaves in regard to probe deferrals. Specifically,
> I dislike the fact that you either register *all domains* or *none at all*
> (unless instantiating two different driver instances and that's ugly).

I don't really like it either, but is it possible to split probe deferrals?
I mean, if you skip a couple power domains because the clocks aren't
available, how do you come back to them?

And IIRC for a clock provider that is _not_ marked as disabled in the DT,
trying to fetch a clock from it would just give -EPROBEDEFER until
the provider is registered.

ChenYu

> >
> > They should be bundled together at the very least. The power domain
> > controller not probing disables all display and multimedia capabilities.
> >
> > Also wondering if we should have "default COMMON_CLK_MT8195" ...
> >
> > I suppose the same questions apply to other SoCs.
> >
> > ChenYu
>
>