Re: [RFC PATCH 2/3] clk: adjust clocks to their requested rate after parent changes

Heiko Stuebner
2016-05-08T20:34:41Z

Am Donnerstag, 5. Mai 2016, 17:49:39 schrieb Doug Anderson:
> Hi,
>
> On Thu, May 5, 2016 at 5:35 PM, Doug Anderson <dianders@chromium.org> wrote:
> > I guess we don't care about errors here?
> >
> > ...maybe (?) we could ignore errors if we validated this rate change
> > with PRE_RATE_CHANGE before attempting to change the parent clock, but
> > I don't see the code doing this unless I missed it.
>
> One other related thought: it seems like there should be code
> _somewhere_ that decides whether to adjust the child dividers before
> or after the parent clock changes. Specifically if the parent clock
> is increasing in speed we probably want to slow down the child clock
> ahead of the parent's increase. I don't see such code here, but again
> I'm pretty good at missing things unless they are slapping me in the
> face. ;)

yep, but that problem of a divider exceeding a requested rate temporarily
exist currently already, even before this change ;-)

Recently we did fix it on a small-scale for composite-clocks though [0].

Heiko

[0] https://git.kernel.org/cgit/linux/kernel/git/clk/linux.git/commit/drivers/clk/clk-composite.c?h=clk-next&id=9e52cec04fd3b9b686f9256151b47fe61f7c28ef