On Thu, Feb 11, 2016 at 04:36:03PM +0200, Jarkko Nikula wrote: > There can be unnecessary runtime suspend-resume cycle during > i2c-designware-platdrv probe when it registers the I2C adapter device. This > happens because i2c-designware-platdrv is set to initially active platform > device in its probe function and is a parent of I2C adapter. > > In that case power.usage_count of i2c-designware device is zero and > pm_runtime_get()/pm_runtime_put() cycle during probe could put it into > runtime suspend. This happens when the i2c_register_adapter() calls the > device_register(): > > i2c_register_adapter > device_register > device_add > bus_probe_device > device_initial_probe > __device_attach > if (dev->parent) pm_runtime_get_sync(dev->parent) > ... > if (dev->parent) pm_runtime_put(dev->parent) > > After that the i2c_register_adapter() continues registering I2C slave > devices. In case slave device probe does I2C transfers the parent will > resume again and thus get a needless runtime suspend/resume cycle during > adapter registration. > > Prevent this while retaining the runtime PM status of i2c-designware by > only incrementing/decrementing device power usage count during I2C > adapter registration. That makes sure there won't be spurious runtime PM > status changes and lets the driver core to idle the device after probe > finishes. > > Signed-off-by: Jarkko Nikula <jarkko.nikula@xxxxxxxxxxxxxxx> I don't know any better way to fix this, Acked-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> -- 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
