Re: [PATCH 08/32] riscv: Fix kernel time_init()

Damien Le Moal
2020-11-13T07:40:21Z

On 2020/11/13 16:31, Stephen Boyd wrote:
> Quoting Damien Le Moal (2020-11-07 00:13:56)
>> If of_clk_init() is not called in time_init(), clock providers defined
>> in the system device tree are not initialized, resulting in failures for
>> other devices to initialize due to missing clocks.
>> Similarly to other architectures and to the default kernel time_init()
>> implementation, call of_clk_init() before executing timer_probe() in
>> time_init().
>
> Do you have timers that need clks to be running or queryable this early?
> This of_clk_init() call is made here when architectures need to call
> things like clk_get_rate() to figure out some clk frequency for their
> clockevent or clocksource. It is OK to have this call here, I'm just
> curious if this is actually necessary vs. delaying it to later.
>

I think the clocks could be initialized later, but at least the CLINT will
depend on one of the clocks, same for the CPU frequency information. So need
checking.

What this patch fixes is not the need for a super early initialization though,
it is that _nothing_ was being initialized without it: the clock driver probe
function was never called with the current riscv time_init() as is. I looked at
other architectures and at the default kernel time_init(), and mimicked what was
done, that is, added of_clk_init(). Is there any other way to make sure that the
needed clock drivers are initialized ?

--
Damien Le Moal
Western Digital Research