Dear Andy
On Mon, 25 Apr 2016 12:07:15 +0300 Andy Shevchenko wrote:
> On Fri, 2016-04-22 at 16:59 +0300, Jarkko Nikula wrote:
> > Hi
> >
> > On 04/22/2016 11:49 AM, Jisheng Zhang wrote:
> > >
> > > If i2c_dw_probe() fails, we should disable and unprepare the clock,
> > > otherwise the clock enable and prepare is left unbalanced.
> > >
> > > In dw_i2c_plat_remove(), we'd better to not rely on runtime PM to
> > > disable and unprepare the clock since CONFIG_PM may be disabled when
> > > configuring the kernel. So we explicitly disable and unprepare the
> > > clock in dw_i2c_plat_remove() rather than implicitly rely on
> > > pm_runtime_put_sync(). To keep the device usage count balanced, we
> > > call pm_runtime_put_noidle() to decrease the usage count.
> > >
> > > Signed-off-by: Jisheng Zhang <jszhang@xxxxxxxxxxx>
> > > ---
> > > Since v3:
> > > - use runtime PM rather than rpm in commit msg
> > > - remove duplicated "(" in commit msg
> > >
> > > Since v2:
> > > - s/clk/clock
> > > - describe why use pm_runtime_put_noidle()
> > >
> > > Since v1:
> > > - fix commit msg: "not rely on rpm" rather than "rely on rpm"
> > > - call i2c_dw_plat_prepare_clk after pm_rumtime_disable()
> > > drivers/i2c/busses/i2c-designware-platdrv.c | 16 ++++++++++------
> > > 1 file changed, 10 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c
> > > b/drivers/i2c/busses/i2c-designware-platdrv.c
> > > index d656657..a771781 100644
> > > --- a/drivers/i2c/busses/i2c-designware-platdrv.c
> > > +++ b/drivers/i2c/busses/i2c-designware-platdrv.c
> > > @@ -253,8 +253,11 @@ static int dw_i2c_plat_probe(struct
> > > platform_device *pdev)
> > > }
> > >
> > > r = i2c_dw_probe(dev);
> > > - if (r && !dev->pm_runtime_disabled)
> > > - pm_runtime_disable(&pdev->dev);
> > > + if (r) {
> > > + if (!dev->pm_runtime_disabled)
> > > + pm_runtime_disable(&pdev->dev);
> > > + i2c_dw_plat_prepare_clk(dev, false);
> > > + }
> > >
> > > return r;
> > > }
> > > @@ -264,15 +267,16 @@ static int dw_i2c_plat_remove(struct
> > > platform_device *pdev)
> > > struct dw_i2c_dev *dev = platform_get_drvdata(pdev);
> > >
> > > pm_runtime_get_sync(&pdev->dev);
> > > + pm_runtime_dont_use_autosuspend(&pdev->dev);
> > > + if (!dev->pm_runtime_disabled)
> > > + pm_runtime_disable(&pdev->dev);
> > > + pm_runtime_put_noidle(&pdev->dev);
> > >
> > > i2c_del_adapter(&dev->adapter);
> > >
> > > i2c_dw_disable(dev);
> > >
> > > - pm_runtime_dont_use_autosuspend(&pdev->dev);
> > > - pm_runtime_put_sync(&pdev->dev);
> > > - if (!dev->pm_runtime_disabled)
> > > - pm_runtime_disable(&pdev->dev);
> > > + i2c_dw_plat_prepare_clk(dev, false);
> > >
> > This feels a bit an invasive change to me for unbalanced clock
> > enable/disable and I noticed this changes semantics how
> > drivers/acpi/acpi_lpss.c devices are shutdown when removing the
> > driver.
> > Although I didn't notice does it cause any regression.
> >
> > Before patch:
> > 1. drivers/base/dd.c: __device_release_driver()
> > - pm_runtime_get_sync()
> > -> acpi_device_set_power(D0)
> > acpi_lpss_restore_ctx()
> > dw_i2c_plat_resume()
> > 2. dw_i2c_plat_remove()
> > - pm_runtime_dont_use_autosuspend()
> > pm_runtime_put_sync()
> > -> dw_i2c_plat_suspend()
> > acpi_lpss_save_ctx()
> > acpi_device_set_power(D3)
> > 3. __device_release_driver() continue
> > - dev->pm_domain->dismiss(dev)
> > -> acpi_lpss_dismiss() ... -> acpi_device_set_power(D3)
> >
> > After patch:
> > 1. drivers/base/dd.c: __device_release_driver()
> > - pm_runtime_get_sync()
> > -> acpi_device_set_power(D0)
> > acpi_lpss_restore_ctx()
> > dw_i2c_plat_resume()
> > 2. dw_i2c_plat_remove()
> > - pm_runtime_dont_use_autosuspend()
> > pm_runtime_put_noidle()
> > * no device suspending and acpi_lpss_save_ctx()
> > 3. __device_release_driver() continue
> > - dev->pm_domain->dismiss(dev)
> > -> acpi_lpss_dismiss() ... -> acpi_device_set_power(D3)
> > * powers down here
> >
> > So after patch there is no acpi_lpss_save_ctx() call but I don't see
> > does it cause any issue here. Maybe it's better to track clock only.
> > What you think Andy?
>
> Now it looks like two fixes in one patch. From the commit message I
> didn't get the relation between change runtime PM call (one to the
> other) and clock (un)preparation.
>
I'm not sure I got your points. There are two unbalanced clk enable and
prepare issues before the patch:
one is in the i2c_dw_probe() failure path. another is in the remove path when
CONFIG_PM is disabled.
The patch addresses this unbalance.
Thanks,
Jisheng
--
To unsubscribe from this list: send the line "unsubscribe linux-i2c" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
