Hi, On 5/14/24 5:21 PM, Andy Shevchenko wrote: > On Tue, May 14, 2024 at 02:33:31PM +0000, Sakari Ailus wrote: >> On Fri, May 10, 2024 at 06:43:31PM +0300, Dan Carpenter wrote: > > ... > >> Neither IPU3-CIO2 or IPU6 ISYS drivers should be of any functional use >> without sensors. But the power states of the devices could be affected by >> this: the drivers should power off these devices but without drivers they >> maybe left powered on. I haven't made any measurements though. > > FWIW, Hans mentioned AtomISPv2 case with somewhat 7W consumption on top of > the idling machine. That's why we have a stub driver in PDx86 exactly for > the purpose of turning it off when not used. I'm not sure if I ever mentioned the 7W, that seems a lot. But in the atomisp case the SoC will never reach S0i3 when the ISP is not properly turned off. And in this case the ISP is special and just letting PCI / ACPI put it in D3 is not enough it needs some special writes on the IO-Sideband-Fabric to be turned off. I don't know if something similar applies to the IPU3 / IPU6, but the bridge code is used by the atomisp code now too. So at a minimum if an error gets returned when there are no sensors then this must be unique enough that the atomisp code can check for it. Maybe -ENODEV ? Regards, Hans
