Re: [PATCH] can: flexcan: enable PER clock before obtaining its rate

[Stephen Boyd <sboyd@kernel.org>]

Quoting Marc Kleine-Budde (2025-04-14 02:55:34)
> On 14.04.2025 10:36:46, Ciprian Costea wrote:
> > From: Ciprian Marian Costea <ciprianmarian.costea@oss.nxp.com>
> > 
> > The FlexCan driver assumes that the frequency of the 'per' clock can be
> > obtained even on disabled clocks, which is not always true.
> > 
> > According to 'clk_get_rate' documentation, it is only valid once the clock
> > source has been enabled.
> 
> In commit bde8870cd8c3 ("clk: Clarify clk_get_rate() expectations")
> Maxime Ripard changed the documentation of the of the function in clk.c
> to say it's allowed. However clk.h states "This is only valid once the
> clock source has been enabled.".
> 
> I've added the common clock maintainers to Cc.
> 
> Which documentation is correct? Is the clk.h correct for archs not using
> the common clock framework?
> 

I don't know what arches not using the common clk framework (CCF) do so
I can't comment there. If you want something to work on an architecture
that doesn't use the CCF then follow the header file, but in all
practical cases _some_ rate will be returned from clk_get_rate() and
we're not going to BUG_ON() or crash the system in the CCF
implementation for this case. Enabling the clk is good hygiene though,
so is it really a problem to enable it here?