On Thu, 2018-01-25 at 16:12 +0800, Zhang Rui wrote: > The .prepare() callback of intel-lpss driver does nothing but wakes up > its > children. I don't know if there is any reason to do so, but to me, > this is > not preferred because it should be the child device driver to do so > when > necessary, not the parent device driver. > Plus, .prepare() does not support asynchronization. > > For example, on MS Surface Pro 4, there are 4 intel-lpss devices which > are runtime suspended before system suspend, resuming each of them > takes > more than 100 milliseconds. Thus the .prepare() of intel-lpss driver > takes > 400ms+ on my surface pro 4, and I've seen platforms with 16 intel lpss > devices. > > With this patch applied, the child devices are resumed in the > .suspend() > stage of the child device, and they are done in parallel, thus only > 100ms > is needed, no matter how many intel lpss devices there are. > > I have tested it on three different platforms and didn't find any > obvious > problem caused by this patch, and it indeed reduces the suspend time a > lot.
> @@ -482,17 +482,6 @@ static int resume_lpss_device(struct device *dev, > - device_for_each_child_reverse(dev, NULL, resume_lpss_device); Besides introduced compiler warning, did you check the latest linux-pm changes? commit 8425ec7faff005500aad89b9fc00e5ba91ac57b9 Author: Rafael J. Wysocki <[email protected]> Date: Wed Jan 3 01:34:53 2018 +0100 PM / mfd: intel-lpss: Use DPM_FLAG_SMART_SUSPEND -- Andy Shevchenko <[email protected]> Intel Finland Oy
