Hi Stephen, Mike,

On Mon, May 24, 2021 at 02:48:11PM +0200, Maxime Ripard wrote:

Hi Stephen, Mike,

On Mon, May 03, 2021 at 10:32:21AM +0200, Maxime Ripard wrote:

quoted

Hi Stephen,

On Fri, Apr 30, 2021 at 01:59:39PM -0700, Stephen Boyd wrote:

quoted

Quoting Maxime Ripard (2021-04-13 03:13:18)

quoted

Hi,

This is a follow-up of the discussion here:
https://lore.kernel.org/linux-clk/20210319150355.xzw7ikwdaga2dwhv@gilmour/ (local)

This implements a mechanism to raise and lower clock rates based on consumer
workloads, with an example of such an implementation for the RaspberryPi4 HDMI
controller.

There's a couple of things worth discussing:

  - The name is in conflict with clk_request_rate, and even though it feels
    like the right name to me, we should probably avoid any confusion

  - The code so far implements a policy of always going for the lowest rate
    possible. While we don't have an use-case for something else, this should
    maybe be made more flexible?

I'm definitely confused how it is different from the
clk_set_rate_exclusive() API and associated
clk_rate_exclusive_get()/clk_rate_exclusive_put(). Can you explain
further the differences in the cover letter here?

The exclusive API is meant to prevent the clock rate from changing,
allowing a single user to make sure that no other user will be able to
change it.

What we want here is instead to allow multiple users to be able to
express a set of minimum rates and then let the CCF figure out a rate
for that clock that matches those constraints (so basically what
clk_set_min_rate does), but then does allow for the clock to go back to
its initial rate once that constraint is not needed anymore.

So I guess it's more akin to clk_set_min_rate with rollback than the
exclusive API?

Is that rationale good enough, or did you expect something else?

I'm not really sure what to do at this point. It's been over 2 months
since I sent this series, and we really need that mechanism in some form
or another.

I'm really fine with changing that series in any way, but I got no
comment that I could address to turn this into something that would be
acceptable to you. How can we move this forward?

Maxime