Re: [PATCH v2 1/1] clk: samsung: exynos850: Register clocks early
From: Sylwester Nawrocki <s.nawrocki@samsung.com>
Date: 2021-11-20 12:49:38
Also in:
linux-arm-kernel, linux-clk, linux-samsung-soc, lkml
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@linaro.org>
quoted hunk ↗ jump to hunk
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