Re: [PATCH v4] i2c: designware-platdrv: fix unbalanced clk enable and prepare

Jarkko Nikula
2016-04-22T13:59:55Z

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@marvell.com>
> ---
> 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?

--
Jarkko