Re: [PATCH v2 1/2] clk: set initial best mux parent to current parent when determining rate

[Yang Xiwen]

On 3/6/2024 10:24 PM, Maxime Ripard wrote:
> Hi,
>
> On Wed, Mar 06, 2024 at 12:22:23AM +0800, Yang Xiwen via B4 Relay wrote:
> > From: Yang Xiwen <forbidden405@xxxxxxxxxxx>
> >
> > Originally, the initial clock rate is hardcoded to 0, this can lead to
> > some problem when setting a very small rate with CLK_MUX_ROUND_CLOSEST.
> >
> > For example, if the lowest possible rate provided by the mux is 1000Hz,
> > setting a rate below 500Hz will fail, because no clock can provide a
> > better rate than the non-existant 0Hz. But it should succeed with 1000Hz
> > being set.
> >
> > Setting the initial best parent to current parent could solve this bug.
> >
> > Signed-off-by: Yang Xiwen <forbidden405@xxxxxxxxxxx>
> That patch makes sense to me, but this changes the behaviour of the function.
>
> Before, if we couldn't find a good configuration for the rate, we were
> error'ing out. Now, we keep the current configuration. We should
> document the new behaviour in the function documentation, and we should
> probably run that through kernelci to make sure we aren't breaking any
> platform (and from experience, we probably are).


We can limit the new behavior to CLK_MUX_ROUND_CLOSEST as well. The 
current behavior is okay for common muxes i think. Though probably wrong 
for CLK_MUX_ROUND_CLOSEST.


> Maxime


--
Regards,
Yang Xiwen