Re: [PATCH] clk: Disambiguate comment about clk_get_rate() for disabled clocks

["Russell King (Oracle)" <linux@armlinux.org.uk>]

On Wed, Feb 01, 2023 at 09:23:09AM +0100, Uwe Kleine-König wrote:
> The sentence "[clk_get_rate()] is only valid once the clock source has
> been enabled." can be understood in two ways:
> 
> a) When called for a disabled clock the return value might be wrong; or
> b) The disabled clock must be enabled before it runs at the returned
> rate.
> 
> It's hard to find evidence what is actually meant, but given that the
> clock tree can change between the call to clk_get_rate() and the return
> of a later clk_enable() call, it's prudent to assume a).
> 
> Adapt the comment accordingly to be unambiguous.

Sorry for the late reply, I've been suffering with Covid for the last
nine days.

From the API perspective, it's both. Essentially, if the clock isn't
enabled, then the return value is completely undefined by the API and
no one should trust it.

It's one of the reasons why:

	clk_set_rate(clk, r);
	v = clk_get_rate(clk);

should not be used when what is actually required is:

	v = clk_round_rate(clk, r);

	...

	clk_set_rate(clk, r);

Note: r to clk_set_rate() not v.

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