On Wed, Jun 24, 2015 at 10:33 AM, Ulf Hansson <ulf.hans...@linaro.org> wrote:
> [...]
>
>>>>
>>>> @@ -2183,6 +2191,7 @@ int genpd_dev_pm_attach(struct device *dev)
>>>> {
>>>> struct of_phandle_args pd_args;
>>>> struct generic_pm_domain *pd;
>>>> + unsigned int i;
>>>> int ret;
>>>>
>>>> if (!dev->of_node)
>>>> @@ -2218,10 +2227,13 @@ int genpd_dev_pm_attach(struct device *dev)
>>>>
>>>> dev_dbg(dev, "adding to PM domain %s\n", pd->name);
>>>>
>>>> - while (1) {
>>>> + for (i = 0; i < GENPD_RETRIES; i++) {
>>>> ret = pm_genpd_add_device(pd, dev);
>>>> if (ret != -EAGAIN)
>>>> break;
>>>> +
>>>> + if (i > GENPD_RETRIES / 2)
>>>> + udelay(GENPD_DELAY_US);
>>>
>>> In this execution path, we retry when getting -EAGAIN while believing
>>> the reason to the error are only *temporary* as we are soon waiting
>>> for all devices in the genpd to be system PM resumed. At least that's
>>> my understanding to why we want to deal with -EAGAIN here, but I might
>>> be wrong.
>>>
>>> In this regards, I wonder whether it could be better to re-try only a
>>> few times but with a far longer interval time than a couple us. What
>>> do you think?
>>
>> That's indeed viable. I have no idea for how long this temporary state can
>> extend.
>
> That will depend on the system PM resume time for the devices residing
> in the genpd. So, I guess we need a guestimate then. How about a total
> sleep time of a few seconds?
>
>>
>>> However, what if the reason to why we get -EAGAIN isn't *temporary*,
>>> because we are about to enter system PM suspend state. Then the caller
>>> of this function which comes via some bus' ->probe(), will hang until
>>> the a system PM resume is completed. Is that really going to work? So,
>>> for this case your limited re-try approach will affect this scenario
>>> as well, have you considered that?
>>
>> There's a limit on the number of retries, so it won't hang indefinitely.
>
> What happens with the timer functions (like msleep()) during the
> system PM suspend transition?
I guess we can no longer call msleep() after syscore suspend?
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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