[PATCH 0/3] PM / ACPI / i2c: Runtime PM aware system sleep handling

[Johannes Stezenbach]

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