Messages in this thread | | | From | Stephen Boyd <> | Subject | Re: [PATCH] clk: at91: avoid sleeping early | Date | Mon, 28 Oct 2019 07:54:55 -0700 |
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Quoting Alexandre Belloni (2019-10-05 13:05:21) > On 24/09/2019 13:20:15-0700, Stephen Boyd wrote: > > Quoting Uwe (2019-09-24 05:21:47) > > > On Fri, Sep 20, 2019 at 05:39:06PM +0200, Alexandre Belloni wrote: > > > > Note that this was already discussed a while ago and Arnd said this approach was > > > > reasonable: > > > > https://lore.kernel.org/lkml/6120818.MyeJZ74hYa@wuerfel/ > > > > > > > > drivers/clk/at91/clk-main.c | 5 ++++- > > > > drivers/clk/at91/sckc.c | 20 ++++++++++++++++---- > > > > 2 files changed, 20 insertions(+), 5 deletions(-) > > > > > > > > diff --git a/drivers/clk/at91/clk-main.c b/drivers/clk/at91/clk-main.c > > > > index f607ee702c83..ccd48e7a3d74 100644 > > > > --- a/drivers/clk/at91/clk-main.c > > > > +++ b/drivers/clk/at91/clk-main.c > > > > @@ -293,7 +293,10 @@ static int clk_main_probe_frequency(struct regmap *regmap) > > > > regmap_read(regmap, AT91_CKGR_MCFR, &mcfr); > > > > if (mcfr & AT91_PMC_MAINRDY) > > > > return 0; > > > > - usleep_range(MAINF_LOOP_MIN_WAIT, MAINF_LOOP_MAX_WAIT); > > > > + if (system_state < SYSTEM_RUNNING) > > > > + udelay(MAINF_LOOP_MIN_WAIT); > > > > + else > > > > + usleep_range(MAINF_LOOP_MIN_WAIT, MAINF_LOOP_MAX_WAIT); > > > > > > Given that this construct is introduced several times, I wonder if we > > > want something like: > > > > > > static inline void early_usleep_range(unsigned long min, unsigned long max) > > > { > > > if (system_state < SYSTEM_RUNNING) > > > udelay(min); > > > else > > > usleep_range(min, max); > > > } > > > > > > > Maybe, but I think the intent is to not encourage this behavior? So > > providing a wrapper will make it "easy" and then we'll have to tell > > users to stop calling it. Another idea would be to make usleep_range() > > "do the right thing" and call udelay if the system isn't running. And > > another idea from tlgx[1] is to pull the delay logic into another clk op > > that we can call to see when the enable or prepare is done. That may be > > possible by introducing another clk_ops callback that when present > > indicates we should sleep or delay for so much time while waiting for > > the prepare or enable to complete. > > > > [1] https://lkml.kernel.org/r/alpine.DEB.2.11.1606061448010.28031@nanos > > > > Do you want me to implement that now or are you planning to apply the > patch in the meantime ? > >
I'll just apply this for now to clk-fixes and merge it up next week. It would be great to do the other idea though, as a long term effort to reduce all the busy loop code we have in clk drivers. No worries, I'll put it on the todo list.
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