Re: [RFT][PATCH 2/2] PM / i2c: designware: Clean up system sleep handling without ACPI

Rafael J. Wysocki
2017-09-04T10:07:21Z

On Monday, September 4, 2017 1:14:44 AM CEST Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> After commit a23318feeff6 (i2c: designware: Fix system suspend)
> the i2c-designware-platdrv driver always resumes the device in its
> system sleep ->suspend callback which isn't particularly nice,
> even though it is technically correct.
>
> A better approach would be to make the driver track the PM state of
> the device so that it doesn't need to resume it in ->suspend and
> to drop its ->prepare and ->complete callbacks which would only be
> marginally useful then, so implement it.
>
> First, drop dw_i2c_plat_suspend() added by commit a23318feeff6 and
> rename dw_i2c_plat_runtime_suspend() back to dw_i2c_plat_suspend().
>
> Second, point the driver's ->late_suspend and ->early_resume
> callbacks, rather than its ->suspend and ->resume callbacks,
> to dw_i2c_plat_suspend() and dw_i2c_plat_resume(), respectively,
> so that they are not executed in parallel with each other, for
> example if runtime resume of the device takes place during system
> suspend. Also, since the driver enables runtime PM unconditionally
> in dw_i2c_plat_probe(), this change allows the
> pm_runtime_status_suspended() check to be used in the PM callbacks
> to determine whether or not the device needs to be either suspended
> or resumed (moving the callbacks into the late/early stages of
> system suspend/resume, respectively, guarantees the stability
> of the runtime PM status at the time when they are invoked).
>
> Next, add a "skip_resume" flag to struct dw_i2c_dev and make
> dw_i2c_plat_suspend() and dw_i2c_plat_resume() use it to avoid
> resuming a previously runtime-suspended device during system resume.
>
> Finally, drop the driver's ->prepare and ->complete PM callbacks,
> because returning "true" from ->prepare for runtime-suspended
> devices is marginally useful (the PM core may still ignore that
> return value and invoke the driver's ->suspend callback anyway)
> and ->complete is only needed because of what ->prepare does.
>
> Overrides: a23318feeff6 (i2c: designware: Fix system suspend)
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
> drivers/i2c/busses/i2c-designware-core.h | 1
> drivers/i2c/busses/i2c-designware-platdrv.c | 47 +++++++++-------------------
> 2 files changed, 17 insertions(+), 31 deletions(-)
>
> Index: linux-pm/drivers/i2c/busses/i2c-designware-core.h
> ===================================================================
> --- linux-pm.orig/drivers/i2c/busses/i2c-designware-core.h
> +++ linux-pm/drivers/i2c/busses/i2c-designware-core.h
> @@ -280,6 +280,7 @@ struct dw_i2c_dev {
> int (*acquire_lock)(struct dw_i2c_dev *dev);
> void (*release_lock)(struct dw_i2c_dev *dev);
> bool pm_disabled;
> + bool skip_resume;
> void (*disable)(struct dw_i2c_dev *dev);
> void (*disable_int)(struct dw_i2c_dev *dev);
> int (*init)(struct dw_i2c_dev *dev);
> Index: linux-pm/drivers/i2c/busses/i2c-designware-platdrv.c
> ===================================================================
> --- linux-pm.orig/drivers/i2c/busses/i2c-designware-platdrv.c
> +++ linux-pm/drivers/i2c/busses/i2c-designware-platdrv.c
> @@ -434,28 +434,17 @@ static const struct of_device_id dw_i2c_
> MODULE_DEVICE_TABLE(of, dw_i2c_of_match);
> #endif
>
> -#ifdef CONFIG_PM_SLEEP
> -static int dw_i2c_plat_prepare(struct device *dev)
> -{
> - return pm_runtime_suspended(dev);
> -}
> -
> -static void dw_i2c_plat_complete(struct device *dev)
> -{
> - if (dev->power.direct_complete)
> - pm_request_resume(dev);
> -}
> -#else
> -#define dw_i2c_plat_prepare NULL
> -#define dw_i2c_plat_complete NULL
> -#endif
> -
> #ifdef CONFIG_PM
> -static int dw_i2c_plat_runtime_suspend(struct device *dev)
> +static int dw_i2c_plat_suspend(struct device *dev)
> {
> struct platform_device *pdev = to_platform_device(dev);
> struct dw_i2c_dev *i_dev = platform_get_drvdata(pdev);
>
> + if (pm_runtime_status_suspended(dev)) {
> + i_dev->skip_resume = true;
> + return 0;
> + }
> +
> i_dev->disable(i_dev);
> i2c_dw_plat_prepare_clk(i_dev, false);
>
> @@ -467,27 +456,23 @@ static int dw_i2c_plat_resume(struct dev
> struct platform_device *pdev = to_platform_device(dev);
> struct dw_i2c_dev *i_dev = platform_get_drvdata(pdev);
>
> + if (!pm_runtime_status_suspended(dev))

This check is incorrect, I've just sent a v2 of the patch.

Sorry about this.

> + return 0;
> +
> + if (i_dev->skip_resume) {
> + i_dev->skip_resume = false;
> + return 0;
> + }
> +
> i2c_dw_plat_prepare_clk(i_dev, true);
> i_dev->init(i_dev);
>
> return 0;
> }
>
> -#ifdef CONFIG_PM_SLEEP
> -static int dw_i2c_plat_suspend(struct device *dev)
> -{
> - pm_runtime_resume(dev);
> - return dw_i2c_plat_runtime_suspend(dev);
> -}
> -#endif
> -
> static const struct dev_pm_ops dw_i2c_dev_pm_ops = {
> - .prepare = dw_i2c_plat_prepare,
> - .complete = dw_i2c_plat_complete,
> - SET_SYSTEM_SLEEP_PM_OPS(dw_i2c_plat_suspend, dw_i2c_plat_resume)
> - SET_RUNTIME_PM_OPS(dw_i2c_plat_runtime_suspend,
> - dw_i2c_plat_resume,
> - NULL)
> + SET_LATE_SYSTEM_SLEEP_PM_OPS(dw_i2c_plat_suspend, dw_i2c_plat_resume)
> + SET_RUNTIME_PM_OPS(dw_i2c_plat_suspend, dw_i2c_plat_resume, NULL)
> };
>
> #define DW_I2C_DEV_PMOPS (&dw_i2c_dev_pm_ops)