Re: [PATCH] clk: at91: clk-generated: Limit the requested rate to our range

[Nicolas Ferre]

On 09/07/2021 at 11:59, Codrin Ciubotariu - M19940 wrote:
> On 09.07.2021 12:21, Nicolas Ferre wrote:
> > On 07/07/2021 at 15:12, Codrin Ciubotariu wrote:
> > > On clk_generated_determine_rate(), the requested rate could be outside
> > > of clk's range. Limit the rate to the clock's range to not return an
> > > error.
> >
> > Isn't it saner for the user to return an error code instead of
> > automatically restrain the dynamics requested without notice?
> >
> > Can you elaborate the use case where returning an error is not convenient?
>
> The way I see it, if the user requests a rate that is out of clock's
> range, the driver's determine_rate() should return min/max, not an
> error. That is actually the closest rate supported by the clock, which
> is what determine_rate() should accomplish. The user has no clk API to
> get clock's range, so there is no way to call clk_round_rate() only for
> values within our range.
>
> The use cause is with sam9x60's I2S driver, which has to try different
> rates to get the closest one to what it needs. There is no 'perfect'
> rate, because there is no AUDIO PLL and we have to try different values
> for our internal dividers to find the closest one.
>
> https://elixir.bootlin.com/linux/latest/source/sound/soc/atmel/mchp-i2s-mcc.c#L416

Sure, makes sense:

Acked-by: Nicolas Ferre <nicolas.ferre@xxxxxxxxxxxxx>

Regards,
  Nicolas

--
Nicolas Ferre