Re: [PATCH 1/3] clk: bcm: rpi: Turn firmware clock on/off when preparing/unpreparing

[Maxime Ripard <mripard@kernel.org>]

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Hi Maíra,

On Mon, Jul 28, 2025 at 09:35:38AM -0300, Maíra Canal wrote:
> Currently, when we prepare or unprepare RPi's clocks, we don't actually
> enable/disable the firmware clock. This means that
> `clk_disable_unprepare()` doesn't actually change the clock state at
> all, nor does it lowers the clock rate.
> 
> From the Mailbox Property Interface documentation [1], we can see that
> we should use `RPI_FIRMWARE_SET_CLOCK_STATE` to set the clock state
> off/on. Therefore, use `RPI_FIRMWARE_SET_CLOCK_STATE` to create a
> prepare and an unprepare hook for RPi's firmware clock.
> 
> As now the clocks are actually turned off, some of them are now marked
> with CLK_IGNORE_UNUSED or CLK_IS_CRITICAL, as those are required since
> early boot or are required during reboot.

What difference is there between the CLK_IGNORE_UNUSED and
CLK_IS_CRITICAL clocks?

I'm asking, because CLK_IGNORE_UNUSED is mostly useless, and
CLK_IS_CRITICAL is probably what you're looking for for all of them.

Maxime

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