On 04/04/2023 11:11, Maxime Ripard wrote:

The Versatile sp810 "timerclken" clock implements a mux with a set_parent hook, but doesn't provide a determine_rate implementation.

This is a bit odd, since set_parent() is there to, as its name implies, change the parent of a clock.

Explanation of this mystery is pretty simple - the original patch:

commit 6e973d2c438502dcf956e76305258ba7d1c7d1d3 Author: Pawel Moll pawel.moll@arm.com Date: Thu Apr 18 18:23:22 2013 +0100

clk: vexpress: Add separate SP810 driver

predates introduction of determine_rate to clk_ops...

commit 71472c0c06cf9a3d1540762ea205654c584e3bc4 Author: James Hogan jhogan@kernel.org Date: Mon Jul 29 12:25:00 2013 +0100

clk: add support for clock reparent on set_rate

and clearly no one (the author included ;-) bothered to have another look at this side of the driver.

And if it was an oversight, then we are at least explicit about our behavior now and it can be further refined down the line.

It's been one hell of a memory lane trip, but my recollection suggest that the main goal of the driver was simply initialisation of the mux to select the 1MHz parent, because the other option - 32kHz - just didn't make any sense whatsoever. And that would be the case on every single platform using SP810 I know (or at least: knew), so it's seems to me that making the state permanent, as you're suggesting (or I think you're suggesting?) it's the right thing to do.

Thanks!

Paweł