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

From: Sylwester Nawrocki
Date: Sat Nov 20 2021 - 12:38:21 EST

On 20.11.2021 17:47, Sam Protsenko wrote:
@@ -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.

Good point, I'll do that in v2. Not sure how I missed that dependency
point, but thank you for noticing that. Guess it only works for me
because clocks are already enabled in bootloader, and I'm using
"clk_ignore_unused" param for now.

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?

If you mean doing clk_prepare_enable() for "dout_peri_bus" clock in
exynos850_cmu_peri_init(), I don't think it's possible. clk_get()
needs "struct device *dev", and we only have that in platform driver
probe. Trying to pass dev=NULL won't work, so that's why I'm enabling
parent clocks in platform driver probe.

Sorry, I didn't notice it earlier, actually CMU_TOP is already being
initialized with OF_CLK_DECLARE.

You could use of_clk_get() to get the clock, the consumer clock indexes
are fixed and defined in the DT binding. There is also
of_clk_get_by_name() which works similarly to clk_get().