13.12.2019 17:04, Dmitry Osipenko пишет: > 13.12.2019 16:47, Thierry Reding пишет: >> On Fri, Dec 13, 2019 at 02:34:28AM +0300, Dmitry Osipenko wrote: >>> I noticed that sometime I2C clock is kept enabled during suspend-resume. >>> This happens because runtime PM defers dynamic suspension and thus it may >>> happen that runtime PM is in active state when system enters into suspend. >>> In particular I2C controller that is used for CPU's DVFS is often kept ON >>> during suspend because CPU's voltage scaling happens quite often. >>> >>> Note: we marked runtime PM as IRQ-safe during the driver's probe in the >>> "Support atomic transfers" patch, thus it's okay to enforce runtime PM >>> suspend/resume in the NOIRQ phase which is used for the system-level >>> suspend/resume of the driver. >>> >>> Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx> >>> --- >>> drivers/i2c/busses/i2c-tegra.c | 9 +++++++++ >>> 1 file changed, 9 insertions(+) >> >> I've recently discussed this with Rafael in the context of runtime PM >> support in the Tegra DRM driver and my understanding is that you're not >> supposed to force runtime PM suspension like this. >> >> I had meant to send out an alternative patch to fix this, which I've >> done now: >> >> http://patchwork.ozlabs.org/patch/1209148/ >> >> That's more in line with what Rafael and I had discussed in the other >> thread and should address the issue that you're seeing as well. > > Well, either me or you are still having some misunderstanding of the > runtime PM :) To my knowledge there are a lot of drivers that enforce > suspension of the runtime PM during system's suspend, it should be a > right thing to do especially in a context of the Tegra I2C driver > because we're using asynchronous pm_runtime_put() and thus at the time > of system's suspending, the runtime PM could be ON (as I wrote in the > commit message) and then Terga's I2C driver manually disables the clock > on resume (woopsie). Actually, looks like it's not the asynchronous pm_runtime_put() is the cause of suspending in active state. I see that only one of three I2C controllers is suspended in the enabled state, maybe some child (I2C client) device keeps it awake, will try to find out. > By invoking pm_runtime_force_suspend() on systems's suspend, the runtime > PM executes tegra_i2c_runtime_suspend() if device is in active state. On > system resume, pm_runtime_force_resume() either keeps device in a > suspended state or resumes it, say if for userspace disabled the runtime > PM for the I2C controller. > > Rafael, could you please clarify whether my patch is doing a wrong thing? > >>> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c >>> index b3ecdd87e91f..d309a314f4d6 100644 >>> --- a/drivers/i2c/busses/i2c-tegra.c >>> +++ b/drivers/i2c/busses/i2c-tegra.c >>> @@ -1790,9 +1790,14 @@ static int tegra_i2c_remove(struct platform_device *pdev) >>> static int __maybe_unused tegra_i2c_suspend(struct device *dev) >>> { >>> struct tegra_i2c_dev *i2c_dev = dev_get_drvdata(dev); >>> + int err; >>> >>> i2c_mark_adapter_suspended(&i2c_dev->adapter); >>> >>> + err = pm_runtime_force_suspend(dev); >>> + if (err < 0) >>> + return err; >>> + >>> return 0; >>> } >>> >>> @@ -1813,6 +1818,10 @@ static int __maybe_unused tegra_i2c_resume(struct device *dev) >>> if (err) >>> return err; >>> >>> + err = pm_runtime_force_resume(dev); >>> + if (err < 0) >>> + return err; >>> + >>> i2c_mark_adapter_resumed(&i2c_dev->adapter); >>> >>> return 0; >>> -- >>> 2.24.0 >>> >
