[PATCH v2 4/5] drivers: firmware: psci: add extended stateid power_state support

Kevin Hilman khilman at kernel.org
Fri Oct 23 08:10:30 PDT 2015

On Fri, Oct 23, 2015 at 4:36 AM, Lorenzo Pieralisi
<lorenzo.pieralisi at arm.com> wrote:
> On Fri, Oct 23, 2015 at 12:55:34PM +0200, Arnd Bergmann wrote:
>> On Friday 23 October 2015 11:44:58 Lorenzo Pieralisi wrote:
>> >
>> > Problem with Qemu emulation is that it does not emulate the PSCI 1.0
>> > specs correctly (it does not even consider PSCI 1.0 functions proper PSCI
>> > calls), I tested it and I think we should update Qemu as we
>> > did with KVM kernel code instead of working around it by dodging the
>> > problem in the PSCI implementation by adding code that checks the
>> > PSCI version before issuing the PSCI calls through the respective
>> > conduit.
>> >
>> > Thoughts appreciated.
>> I think we really cannot break existing qemu installations, but need
>> a way to detect whether we are dealing with a broken qemu (and warn
>> about that) or with a working PSCI implementation.
>> Fixing qemu is of course a good idea, but it's not sufficient.
> I will patch the PSCI back-end in the kernel to issue PSCI_FEATURES calls
> only if the PSCI version detected is 1.0, therefore solving the issue, it
> is not necessary according to the specs, but that's belt and braces
> and sorts this niggle out.
> I will send a patch shortly to be applied on top of arm-soc drivers/psci.


In parallel, since you understandn better what qemu is/isn't doing,
can you ping the qemu folks about this bug?



More information about the linux-arm-kernel mailing list