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. Acked-by: Mika Westerberg <mika.westerb...@linux.intel.com> Reviewed-by: Andy Shevchenko <andriy.shevche...@linux.intel.com> Cc: Andy Shevchenko <andriy.shevche...@linux.intel.com> Cc: Mika Westerberg <mika.westerb...@linux.intel.com> Cc: Rafael J. Wysocki <rafael.j.wyso...@intel.com> Signed-off-by: Chen Yu <yu.c.c...@intel.com> --- drivers/mfd/intel-lpss.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/mfd/intel-lpss.c b/drivers/mfd/intel-lpss.c index 41b1138..2ba8d19 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 RPM_SUSPENDED; + /* * Resume both child devices before entering system sleep. This * ensures that they are in proper state before they get suspended. */ -- 2.7.4