We have report that the intel_lpss_prepare() takes too much time during suspend, and this is because we first resume the devices from runtime suspend by resume_lpss_device(), to make sure they are in proper state before system suspend, which takes 100ms for each LPSS devices(PCI power state from D3_cold to D0). And since resume_lpss_device() resumes the devices synchronously, we might get huge latency if we have many LPSS devices.
So first try is to use pm_request_resume() instead, to make the runtime resume process asynchronously. Unfortunately the asynchronous runtime resume relies on pm_wq, which is freezed at early stage. So we choose another method, that is to avoid resuming runtime-suspended devices, if they are already runtime suspended. This is safe because for LPSS driver, the runtime suspend and system suspend are of the same hook - i.e., intel_lpss_suspend(). And moreover, this device is neither runtime wakeup source nor system wakeup source. Suggested-by: Rafael J. Wysocki <[email protected]> Acked-by: Mika Westerberg <[email protected]> Reviewed-by: Andy Shevchenko <[email protected]> Cc: Andy Shevchenko <[email protected]> Cc: Mika Westerberg <[email protected]> Cc: Rafael J. Wysocki <[email protected]> Cc: Lee Jones <[email protected]> Signed-off-by: Chen Yu <[email protected]> --- drivers/mfd/intel-lpss.c | 9 +++++++++ include/linux/pm.h | 3 +++ 2 files changed, 12 insertions(+) diff --git a/drivers/mfd/intel-lpss.c b/drivers/mfd/intel-lpss.c index 41b1138..2583db8 100644 --- a/drivers/mfd/intel-lpss.c +++ b/drivers/mfd/intel-lpss.c @@ -485,6 +485,15 @@ static int resume_lpss_device(struct device *dev, void *data) int intel_lpss_prepare(struct device *dev) { /* + * This is safe because: + * 1. The runtime suspend and system suspend + * are of the same hook. + * 2. This device is neither runtime wakeup source + * nor system wakeup source. + */ + if (pm_runtime_status_suspended(dev)) + return DPM_DIRECT_COMPLETE; + /* * Resume both child devices before entering system sleep. This * ensures that they are in proper state before they get suspended. */ diff --git a/include/linux/pm.h b/include/linux/pm.h index 06eb353..5606ad9 100644 --- a/include/linux/pm.h +++ b/include/linux/pm.h @@ -786,4 +786,7 @@ enum dpm_order { DPM_ORDER_DEV_LAST, }; +/* The device is OK to remain runtime-suspended during suspend.*/ +#define DPM_DIRECT_COMPLETE 1 + #endif /* _LINUX_PM_H */ -- 2.7.4
