Re: [PATCH AUTOSEL 5.16 02/52] clk: samsung: exynos850: Register clocks early

[Sasha Levin]

On Mon, Jan 17, 2022 at 09:18:43PM +0200, Sam Protsenko wrote:
> On Mon, 17 Jan 2022 at 19:11, Krzysztof Kozlowski
> <krzysztof.kozlowski@xxxxxxxxxxxxx> wrote:
> > On 17/01/2022 17:58, Sasha Levin wrote:
> > > From: Sam Protsenko <semen.protsenko@xxxxxxxxxx>
> > >
> > > [ Upstream commit bcda841f9bf2cddcf2f000cba96f2e27f6f2bdbf ]
> > >
> > > Some clocks must be registered before init calls. For example MCT clock
> > > (from CMU_PERI) is needed for MCT timer driver, which is registered
> > > with TIMER_OF_DECLARE(). By the time we get to core_initcall() used for
> > > clk-exynos850 platform driver init, it's already too late. Inability to
> > > get "mct" clock in MCT driver leads to kernel panic, as functions
> > > registered with *_OF_DECLARE() can't do deferred calls. MCT timer driver
> > > can't be fixed either, as it's acting as a clock source and it's
> > > essential to register it in start_kernel() -> time_init().
> > >
> > > Let's register CMU_PERI clocks early, using CLK_OF_DECLARE(). CMU_TOP
> > > generates clocks needed for CMU_PERI, but it's already registered early.
> > >
> > > While at it, let's cleanup the code a bit, by extracting everything
> > > related to CMU initialization and registration to the separate function.
> > >
> > > Similar issue was discussed at [1] and addressed in commit 1f7db7bbf031
> > > ("clk: renesas: cpg-mssr: Add early clock support"), as well as in
> > > drivers/clk/mediatek/clk-mt2712.c.
> > >
> > > [1] https://patchwork.kernel.org/project/linux-renesas-soc/patch/20180829132954.64862-2-chris.brandt@xxxxxxxxxxx/
> > >
> > > Signed-off-by: Sam Protsenko <semen.protsenko@xxxxxxxxxx>
> > > Signed-off-by: Sylwester Nawrocki <s.nawrocki@xxxxxxxxxxx>
> > > Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxxxxx>
> > > Link: https://lore.kernel.org/r/20211122144206.23134-1-semen.protsenko@xxxxxxxxxx
> > > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
> > > ---
> > >  drivers/clk/samsung/clk-exynos850.c | 70 ++++++++++++++++++++---------
> > >  1 file changed, 49 insertions(+), 21 deletions(-)
> > >
> >
> > I propose to skip this one.
> >
> > Backporting it to v5.16 does not hurt but also does not bring any
> > benefits for the upstream kernel users. There is no support for
> > mentioned Exynos850 in v5.16.
> >
> > It could have only meaning for some downstream, out-of-tree kernels
> > which apply Exynos850 support on top of v5.16, but then they can just
> > take this patch as well.
>
> Agreed. DTS patches will be merged only in v5.17, hopefully. Till that
> time the whole clock driver is floating with no users. That's
> historical thing -- I didn't have "Ack" to submit board dts at the
> time, and SoC dts couldn't be applied without users (board dts). So I
> focused on driver work, isolated. Not much sense to backport something
> without having real users.

Dropped, thanks!

--
Thanks,
Sasha