On Mon, 12 Sep 2016, Chen Yu wrote:
On Mon, Sep 12, 2016 at 04:17:04PM +0100, Lee Jones wrote:Are there no defines for this?
On Sun, 04 Sep 2016, Chen Yu wrote:According to the comment in device_prepare():
We have report that the intel_lpss_prepare() takes too much time duringWhat's '1'?
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
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.
Cc: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Cc: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>
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..6dcc9a0 100644
@@ -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 1;
A positive return value from ->prepare() means "this device appears
to be runtime-suspended and its state is fine, so if it really is
runtime-suspended, you can leave it in that state provided that you
will do the same thing with all of its descendants".