Re: [PATCH 112/114] clk: scmi: remove round_rate() in favor of determine_rate()

[Brian Masney <bmasney@redhat.com>]

On Wed, Aug 27, 2025 at 03:09:33PM +0800, Peng Fan wrote:
> Hi Brian, Sudeep, Cristian
> 
> On Mon, Aug 11, 2025 at 11:19:44AM -0400, Brian Masney via B4 Relay wrote:
> >From: Brian Masney <bmasney@redhat.com>
> >
> >This driver implements both the determine_rate() and round_rate() clk
> >ops, and the round_rate() clk ops is deprecated. When both are defined,
> >clk_core_determine_round_nolock() from the clk core will only use the
> >determine_rate() clk ops, so let's remove the round_rate() clk ops since
> >it's unused.
> >
> >Signed-off-by: Brian Masney <bmasney@redhat.com>
> >---
> > drivers/clk/clk-scmi.c | 30 ------------------------------
> > 1 file changed, 30 deletions(-)
> >
> >diff --git a/drivers/clk/clk-scmi.c b/drivers/clk/clk-scmi.c
> >index d2408403283fc72f0cf902e65f4c08bcbc7b4b0b..6c6ddb92e7cf6a0cfac2c7e19c0f15f777bb8c51 100644
> >--- a/drivers/clk/clk-scmi.c
> >+++ b/drivers/clk/clk-scmi.c
> >@@ -54,35 +54,6 @@ static unsigned long scmi_clk_recalc_rate(struct clk_hw *hw,
> > 	return rate;
> > }
> > 
> >-static long scmi_clk_round_rate(struct clk_hw *hw, unsigned long rate,
> >-				unsigned long *parent_rate)
> >-{
> 
> I see the point of round_rate is not used if determine_rate is there.
> But reading the code of round_rate, It might be better to rename
> scmi_clk_round_rate to scmi_clk_determine_rate.
> 
> Anyway, need Sudeep and Cristian to comment.

In this case, yes the round_rate implementation is filled out, whereas
the determine_rate lets the firmware handle it, and
scmi_clk_recalc_rate() will later populate the rate the clock is running
at.

I can convert round_rate over to determine_rate in this case, however it
would be a change to what's there now, and risks a regression. Here's
the relevant code from drivers/clk/clk.c where the determine_rate and
round_rate ops are called:

    static int clk_core_determine_round_nolock(struct clk_core *core,
                                               struct clk_rate_request *req)
    {
    	...
            if (clk_core_rate_is_protected(core)) {
                    req->rate = core->rate;
            } else if (core->ops->determine_rate) {
                    return core->ops->determine_rate(core->hw, req);
            } else if (core->ops->round_rate) {
                    rate = core->ops->round_rate(core->hw, req->rate,
                                                 &req->best_parent_rate);
    	...

If Sudeep / Cristian want the round rate converted to determine rate in
this driver, then I can do that in a v2.

Brian