On 13:47-20251223, Michael Walle wrote: > The TISCI firmware will return 0 if the clock or consumer is not > enabled although there is a stored value in the firmware. IOW a call to > set rate will work but at get rate will always return 0 if the clock is > disabled. > The clk framework will try to cache the clock rate when it's requested > by a consumer. If the clock or consumer is not enabled at that point, > the cached value is 0, which is wrong. Thus, disable the cache > altogether. > > Signed-off-by: Michael Walle <[email protected]> > Reviewed-by: Kevin Hilman <[email protected]> > Reviewed-by: Randolph Sapp <[email protected]> > --- > drivers/clk/keystone/sci-clk.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/clk/keystone/sci-clk.c b/drivers/clk/keystone/sci-clk.c > index 9d5071223f4c..0a1565fdbb3b 100644 > --- a/drivers/clk/keystone/sci-clk.c > +++ b/drivers/clk/keystone/sci-clk.c > @@ -333,6 +333,14 @@ static int _sci_clk_build(struct sci_clk_provider > *provider, > > init.ops = &sci_clk_ops; > init.num_parents = sci_clk->num_parents; > + > + /* > + * A clock rate query to the SCI firmware will return 0 if either the > + * clock itself is disabled or the attached device/consumer is disabled. > + * This makes it inherently unsuitable for the caching of the clk > + * framework. > + */ > + init.flags = CLK_GET_RATE_NOCACHE; > sci_clk->hw.init = &init; > > ret = devm_clk_hw_register(provider->dev, &sci_clk->hw); > -- > 2.47.3 >
Reviewed-by: Nishanth Menon <[email protected]> I wish there was a better scheme, but inherently, just like SCMI and other systems where power management co-processor controls clocks, there is no real feasible caching scheme I can think of. I wonder if Stephen or others have a thought on this? That said, I wonder if we need fixes tag to this? I am sure there are other clocks susceptible to this as well. I wonder if commit 3c13933c6033 ("clk: keystone: sci-clk: add support for dynamically probing clocks") is the appropriate tag? -- Regards, Nishanth Menon Key (0xDDB5849D1736249D) / Fingerprint: F8A2 8693 54EB 8232 17A3 1A34 DDB5 849D 1736 249D https://ti.com/opensource
