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.
> Signed-off-by: Sam Protsenko <semen.protsenko@xxxxxxxxxx>
> drivers/clk/samsung/clk-exynos850.c | 17 +++++++++++++++--
> 1 file changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/clk/samsung/clk-exynos850.c b/drivers/clk/samsung/clk-exynos850.c
> index 95e373d17b42..ecffa5c7a081 100644
> --- a/drivers/clk/samsung/clk-exynos850.c
> +++ b/drivers/clk/samsung/clk-exynos850.c
> @@ -753,6 +753,15 @@ static const struct samsung_cmu_info peri_cmu_info __initconst = {
> .clk_name = "dout_peri_bus",
> };
>
> +static void __init exynos850_cmu_peri_init(struct device_node *np)
> +{
> + exynos850_init_clocks(np, peri_clk_regs, ARRAY_SIZE(peri_clk_regs));
> + samsung_cmu_register_one(np, &peri_cmu_info);
> +}
> +
> +CLK_OF_DECLARE_DRIVER(exynos850_cmu_peri, "samsung,exynos850-cmu-peri",
> + exynos850_cmu_peri_init);
> +
> /* ---- CMU_CORE ------------------------------------------------------------ */
>
> /* Register Offset definitions for CMU_CORE (0x12000000) */
> @@ -920,8 +929,12 @@ static int __init exynos850_cmu_probe(struct platform_device *pdev)
> struct device_node *np = dev->of_node;
>
> info = of_device_get_match_data(dev);
> - exynos850_init_clocks(np, info->clk_regs, info->nr_clk_regs);
> - samsung_cmu_register_one(np, info);
> +
> + /* Early clocks are already registered using CLK_OF_DECLARE_DRIVER() */
> + if (info != &peri_cmu_info) {
> + exynos850_init_clocks(np, info->clk_regs, info->nr_clk_regs);
> + samsung_cmu_register_one(np, info);
> + }
Don't you also need to register early CMU_TOP, which provides clocks
for CMU_PERI? I'm afraid it might not work properly when you register
CMU_PERI clocks early and only later in probe() you enable parent clock
required for the already registered clocks to be usable.
How about registering also CMU_TOP early and enabling parent clock
also in OF_CLK_DECLARE init callback, i.e. using either OF_CLK_DECLARE
or platform driver for a CMU?
--
Regards,
Sylwester
