Hi, On Tue, Aug 29, 2017 at 02:18:13AM +0200, Rafael J. Wysocki wrote: > On Wednesday, August 23, 2017 4:42:00 PM CEST Ulf Hansson wrote: > > The i2c designware platform driver, drivers/i2c/busses/i2c-designware-platdrv.c, > > isn't well optimized for system sleep. > > > > What makes this driver particularly interesting is because it's a cross-SoC > > driver, which sometimes means there is an ACPI PM domain attached to the i2c > > device and sometimes not. The driver is being used on both x86 and ARM. ... > Basically, the point is to allow i2c-designware-platdrv to point its late > suspend and early resume callbacks, respectively, to pm_runtime_force_suspend() > and pm_runtime_force_resume() which then will do the right thing regardless of > whether or not the device is runtime suspended when system suspend starts. I'd like to point out a comment added by Hans de Goede in https://bugzilla.kernel.org/show_bug.cgi?id=193891#c99 The D0 / D3 methods of some devices use ACPI OpRegions on the PMIC which is attached to I2C7, these methods get executed by acpi_dev_suspend_late / acpi_dev_resume_early. Since the i2c-designware driver uses regular suspend / resume callbacks it is already suspended at the time those calls happen, leading to a device-suspend error and the system not suspending at all. It's the reason for the Cherrytrail I2C7 special treatment in i2c-designware-platdrv.c and pm_disabled = true in i2c-designware-baytrail.c, however pm_disabled seems to be a problem for S0ix support. To solve it, i2c-designware-platdrv needs to suspend after all devices using ACPI OpRegions for suspend. Johannes
