Re: [PATCH v2 1/1] clk: samsung: exynos850: Register clocks early

[Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>]

On 25/10/2021 18:12, Sam Protsenko wrote:
> 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_DRIVER(), and
> do all stuff relying on "struct dev" object (like runtime PM and
> enabling bus clock) later in platform driver probe. Basically
> CLK_OF_DECLARE_DRIVER() matches CMU compatible, but clears OF_POPULATED
> flag, which allows the same device to be matched again later.
> 
> 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@renesas.com/
> 
> Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
> ---
> Changes in v2:
>   - Register only CMU_PERI clocks early
> 
> Notes:
>   - This patch should be applied on top of CMU_APM series
>     (clk: samsung: exynos850: Implement CMU_APM domain)
> 
>  drivers/clk/samsung/clk-exynos850.c | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
> 


Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>


Best regards,
Krzysztof