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

Rafael J. Wysocki
2017-09-03T23:14:44Z

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))
+ 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)