Hi Andy, On 07 July 2022 08:21 Phil Edworthy wrote: > On 03 July 2022 16:17 Andy Shevchenko wrote: > > On Sun, Jul 03, 2022 at 10:41:45AM +0200, Geert Uytterhoeven wrote: > > > On Sat, Jul 2, 2022 at 1:51 PM Andy Shevchenko > > > <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote: > > > > On Fri, Jul 01, 2022 at 05:39:16PM +0100, Phil Edworthy wrote: > > > > > Yet another i2c controller from Renesas that is found on the > RZ/V2M > > > > > (r9a09g011) SoC. It can support only 100kHz and 400KHz operation. > > > > ... > All other suggested changes are ok. > > > > > > > + pm_runtime_get_sync(dev); > > > > > > pm_runtime_resume_and_get() ;-) > > > > This makes sense only if we test for error. Otherwise the put might > > imbalance > > counter. > I added code to check the return value and to my surprise it returned > -EACCES. > Some digging later, this only happens when I have an i2c controller > enabled that doesn't have any children. > > rpm_resume() returns -EACCES [1] because runtime_status and last_status > are set to RPM_SUSPENDED. > > The i2c controller that does have a child has runtime_status = RPM_ACTIVE > as there is a call to pm_runtime_resume_and_get() on it due to the i2c > controller performing an i2c transfer for the slave device. > > I am currently struggling to work out why this is happening... First pm_suspend() works it's way down to __pm_runtime_disable(): __pm_runtime_disable+0x134/0x1e0 __device_suspend_late+0x28/0x1c4 dpm_suspend_late+0x158/0x230 suspend_devices_and_enter+0x1c8/0x4b4 pm_suspend+0x210/0x28c At the end of which, runtime_status and last_status are both RPM_SUSPENDED, and disable_depth = 1 [1] After that rzv2m_i2c_suspend() is called triggering the EACCES error condition [2]: rpm_resume+0x338/0x630 __pm_runtime_resume+0x4c/0x80 rzv2m_i2c_suspend+0x24/0xb0 pm_generic_suspend_noirq+0x30/0x50 genpd_finish_suspend+0xb0/0x130 genpd_suspend_noirq+0x14/0x20 __device_suspend_noirq+0x68/0x1d0 dpm_noirq_suspend_devices+0x110/0x1dc dpm_suspend_noirq+0x24/0xa0 suspend_devices_and_enter+0x2f0/0x4b4 pm_suspend+0x210/0x28c I think using runtime PM from within driver suspend/resume is simply not supported. However I had some difficulty following the runtime PM code, so I could be wrong. Phil [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/base/power/runtime.c?h=v5.19-rc5#n1466 [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/base/power/runtime.c?h=v5.19-rc5#n773
