Re: [PATCH v13 06/35] clk: tegra: Support runtime PM and power domain

Dmitry Osipenko
2021-10-06T21:20:38Z

06.10.2021 15:38, Ulf Hansson пишет:
> In principle what you ask for, is if we can avoid calling
> __pm_runtime_disable() in __device_suspend_late() (and vice versa in
> device_resume_early()).
>
> I think the short answer is no, at least from a generic point of view.
> Maybe we can figure out a way to allow this on a per device basis, as
> an opt-in solution. I am not sure what Rafael would think about this,
> let's see.
>
> Another option to address the problem is already available to use for
> these kinds of cases. This would be to add also a pair of
> ->suspend|resume() callbacks to I2C driver. Along the lines of the
> below.
>
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index c883044715f3..589bf872ab25 100644
> --- a/drivers/i2c/busses/i2c-tegra.c
> +++ b/drivers/i2c/busses/i2c-tegra.c
> @@ -1918,6 +1918,7 @@ static int __maybe_unused
> tegra_i2c_resume(struct device *dev)
> }
>
> static const struct dev_pm_ops tegra_i2c_pm = {
> + SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_put_noidle, pm_runtime_get_sync)
> SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(tegra_i2c_suspend, tegra_i2c_resume)
> SET_RUNTIME_PM_OPS(tegra_i2c_runtime_suspend, tegra_i2c_runtime_resume,
> NULL)
>
> In this way, the device would already be runtime resumed, if there is
> call to pm_runtime_get_sync() from the clock framework due to the
> clk_prepare|unprepare() being called. If that also turns out to happen
> *after* runtime PM has been disabled for the device, the call to
> pm_runtime_get_sync() would still succeed (returning 1, see
> rpm_resume()), rather than a negative error code.
>
> Yes, we may end up runtime resuming the device during system suspend,
> even if it turns out not to be needed. Although, that doesn't seem to
> be the case for the Tegra I2C driver, right?

Tegra I2C will turn off clocks on suspend regardless of RPM state.
Overall, it's a plausible solution, thank you!

As I said in the other reply, I'll simply remove the suspend ops from
clk driver, they are not needed anymore. The problem is gone.