On Tuesday 29 March 2016 06:59:15 okaya@xxxxxxxxxxxxxx wrote: > On 2016-03-29 05:25, Arnd Bergmann wrote: > > On Monday 28 March 2016 09:35:22 Sinan Kaya wrote: > >> The code is using the compatible DT string to associate a reset driver > >> with > >> the actual device itself. The compatible string does not exist on ACPI > >> based systems. HID is the unique identifier for a device driver > >> instead. > >> The change allows a driver to register with DT compatible string or > >> ACPI > >> HID and then match the object with one of these conditions. > >> > >> Rules for loading the reset driver are as follow: > >> - ACPI HID needs match for ACPI systems > >> - DT compat needs to match for OF systems > >> > >> Tested-by: Eric Auger <eric.auger@xxxxxxxxxx> (device tree only) > >> Tested-by: Shanker Donthineni <shankerd@xxxxxxxxxxxxxx> (ACPI only) > >> Signed-off-by: Sinan Kaya <okaya@xxxxxxxxxxxxxx> > >> > > > > > > This really feels wrong for two reasons: > > > > * device assignment of non-PCI devices is really special and doesn't > > seem to make sense on general purpose servers that would be the > > target > > for ACPI normally > > > Why is it special? Acpi is not equal to pci. Platform devices are first > class devices too. Especially, _cls was introduced for this reason. It still feels like a hack. The normal design for a server is to have all internal devices show up on the PCI host bridge, next to the PCIe ports, to have a simple way to manage any device, both internal and off-chip. Putting a device on random MMIO registers outside of the discoverable buses and have the firmware work around the lack of discoverability will always be inferior. > > > > * If there is indeed a requirement for ACPI to handle something like > > this, > > it should be part of the ACPI spec, with a well-defined method of > > handling > > reset, rather than having to add a device specific hack for each > > device separately. > > > > I see. Normally, this is done by calling _rst method. AFAIK, Linux > doesn’t support _rst. I can check its presence and call it if it is > there. Yes, that sounds reasonable: In patch 2 where you check for the presence of the reset method, just keep the existing logic for DT based systems, and use _rst on ACPI based systems instead, then you can drop both patches 1 and 3. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
