On Sat, 4 Sep 2010 01:10:10 +0200, Rafael J. Wysocki wrote: > On Friday, September 03, 2010, Sripathy, Vishwanath wrote: > > We are seeing one more issue even after making this fix. In summary, after > > first suspend/resume, CPU Idle no longer works since i2c module is active. > > Basically when the system resumed from the suspend, dpm layer > > (dpm_resume_end) calls device_resume which intern calls > > i2c_device_pm_resume (among many other calls). > > i2c_device_pm_resume calls pm_runtime_set_active which brings device to > > Active state and increases child_count of it's parent. Since the device is > > active and also it's parent child_count is non 0, these modules will > > prevent corresponding clock domains to go idle. This will break CPU Idle. > > This issue happens even if the module was in idle state before performing > > suspend/resume. In summary, the flow is > > 1. i2c module is idle (let's assume system is idle) > > 2. system suspend is initiated by user > > 3. i2c_device_pm_suspend gets called which tries to idle i2c, but it's > > already idled. > > 4. system is suspended > > 5. system resumed (because of user event/timers) > > 6. dpm layer will call i2c_device_pm_resume > > 7. i2c_device_pm_resume will enable i2c device by calling > > pm_runtime_set_active > > So at the end of suspend/resume, a device that was idled before is getting > > enabled unnecessarily at the end. > > > > SO I am just wondering is there any real need to call pm_runtime_set_active > > in resume and pm_runtime_set_suspened in suspend functions? > > I just tried suspend/resume and CPU Idle after removing these calls in i2c > > and it seems to function perfectly fine on OMAP4. > > Your analysis appears to be entirely correct. > > So, instead of applying the $subject patch it might be better to remove the > block that calls pm_runtime_set_active(dev) from i2c_device_pm_resume(). > > Are there any objections?
No objection. Just send an updated patch and I'll be happy to apply it. -- Jean Delvare -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
