Hi Lina,
On Tue, Oct 25, 2016 at 12:21 AM, Lina Iyer <lina.iyer@xxxxxxxxxx> wrote:
> Generic Power Domains currently support turning on/off only in process
> context. This prevents the usage of PM domains for domains that could be
> powered on/off in a context where IRQs are disabled. Many such domains
> exist today and do not get powered off, when the IRQ safe devices in
> that domain are powered off, because of this limitation.
>
> However, not all domains can operate in IRQ safe contexts. Genpd
> therefore, has to support both cases where the domain may or may not
> operate in IRQ safe contexts. Configuring genpd to use an appropriate
> lock for that domain, would allow domains that have IRQ safe devices to
> runtime suspend and resume, in atomic context.
>
> To achieve domain specific locking, set the domain's ->flag to
> GENPD_FLAG_IRQ_SAFE while defining the domain. This indicates that genpd
> should use a spinlock instead of a mutex for locking the domain. Locking
> is abstracted through genpd_lock() and genpd_unlock() functions that use
> the flag to determine the appropriate lock to be used for that domain.
>
> Domains that have lower latency to suspend and resume and can operate
> with IRQs disabled may now be able to save power, when the component
> devices and sub-domains are idle at runtime.
>
> The restriction this imposes on the domain hierarchy is that non-IRQ
> safe domains may not have IRQ-safe subdomains, but IRQ safe domains may
> have IRQ safe and non-IRQ safe subdomains and devices.
>
> Cc: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> Cc: Kevin Hilman <khilman@xxxxxxxxxx>
> Cc: Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>
> Signed-off-by: Lina Iyer <lina.iyer@xxxxxxxxxx>
> Acked-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> ---
> drivers/base/power/domain.c | 111 ++++++++++++++++++++++++++++++++++++++++----
> include/linux/pm_domain.h | 10 +++-
> 2 files changed, 110 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index 1ad42f2..07ed835 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -74,11 +74,70 @@ static const struct genpd_lock_ops genpd_mtx_ops = {
> +static inline bool irq_safe_dev_in_no_sleep_domain(struct device *dev,
> + struct generic_pm_domain *genpd)
> +{
> + bool ret;
> +
> + ret = pm_runtime_is_irq_safe(dev) && !genpd_is_irq_safe(genpd);
> +
> + /* Warn once for each IRQ safe dev in no sleep domain */
This comment is not correct, as dev_warn_once() will print the warning once,
not once per device. Hence users will not be informed if there are multiple
IRQ safe devices.
> + if (ret)
> + dev_warn_once(dev, "PM domain %s will not be powered off\n",
> + genpd->name);
BTW, I'm seeing messages like:
sh_cmt ffca0000.timer: PM domain always-on will not be powered off
and
sh_cmt e6138000.timer: PM domain c5 will not be powered off
on various Renesas SoCs, and wanted to know if there was more than one
IRQ safe device preventing a PM domain power down (answer: there isn't).
Note that the above are OK, as both "always-on" and "c5" are always-on
PM domains.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
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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