+ linux-pm, Rafael, Kevin
On 23 May 2016 at 14:59, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
> The runtime suspend of the hardware (declocking and pin control
> resting) needs to happen in the *_noirq callbacks after all
> hardware interrupts are disabled and we know there will be no
> more I2C traffic in the system.
As you need this change, it means some other device requires the I2C
device to be runtime resumed, while a *_late callback tries to suspend
the other device. Right!?
Can you tell which these devices are?
Moving the suspend operations to the *_noirq callbacks could improve
the situation, but unfortunate it's comes with a limitation.
That's because runtime PM has been disabled (by genpd or the PM core)
before the *_late callbacks is invoked, which means the I2C device
needs to be runtime resumed in an earlier phase to make it
operational.
This is indeed a generic problem, as we don't have a way to describe
these kind of dependences between devices. In other words, we need to
control the order of how devices becomes suspended/resumed. If that
could be done, we could likely avoid runtime resuming devices
unnecessarily.
Kind regards
Uffe
>
> Cc: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
> ---
> drivers/i2c/busses/i2c-nomadik.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-nomadik.c b/drivers/i2c/busses/i2c-nomadik.c
> index bcd17e8cbcb4..c96a3e331bed 100644
> --- a/drivers/i2c/busses/i2c-nomadik.c
> +++ b/drivers/i2c/busses/i2c-nomadik.c
> @@ -877,7 +877,7 @@ static irqreturn_t i2c_irq_handler(int irq, void *arg)
> }
>
> #ifdef CONFIG_PM_SLEEP
> -static int nmk_i2c_suspend_late(struct device *dev)
> +static int nmk_i2c_suspend_noirq(struct device *dev)
> {
> int ret;
>
> @@ -889,7 +889,7 @@ static int nmk_i2c_suspend_late(struct device *dev)
> return 0;
> }
>
> -static int nmk_i2c_resume_early(struct device *dev)
> +static int nmk_i2c_resume_noirq(struct device *dev)
> {
> return pm_runtime_force_resume(dev);
> }
> @@ -931,7 +931,8 @@ static int nmk_i2c_runtime_resume(struct device *dev)
> #endif
>
> static const struct dev_pm_ops nmk_i2c_pm = {
> - SET_LATE_SYSTEM_SLEEP_PM_OPS(nmk_i2c_suspend_late, nmk_i2c_resume_early)
> + SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(nmk_i2c_suspend_noirq,
> + nmk_i2c_resume_noirq)
> SET_RUNTIME_PM_OPS(nmk_i2c_runtime_suspend,
> nmk_i2c_runtime_resume,
> NULL)
> --
> 2.4.11
>
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