On Mon, Jun 30, 2014 at 12:19:15PM -0400, Jon Masters wrote:

On 6/11/14, 5:06 AM, Arnd Bergmann wrote:

quoted

On Wednesday 11 June 2014 10:16:03 Paolo Bonzini wrote:

quoted

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If kernels actually do use the UEFI runtime services and have no need
for direct access to an RTC when runing in a UEFI compliant system, then
I agree with not specifying the hardware details.

The RTC is not needed for ordinary operation of the kernel and, in the
current kernel, the EFI RTC driver is only used for IA64.  However, it
seems to be platform independent.  I'll give it a shot (on x86, since
that's the only architecture for which I know how to get UEFI firmware).

Using the EFI RTC seems appropriate for ARM, as it's a reasonable
abstraction that should work with any hypervisor. I suspect the only
reason we don't use it on x86 is that we know which RTC hardware we
have and the kernel comes with a mandatory driver already.

(sorry for delay in responding to this thread)

Indeed. We should use the EFI RTC driver in general, rather than
push for many individual RTC drivers on aarch64 systems that are EFI
enabled. Within Red Hat, we currently have EFI Runtime Services live
in many of our labs and are using the EFI RTC. This is the way
forward.

Seems like we should stick a note in there about being UEFI compatible
requires an RTC.  We went this far before Peter raised the issue with
noone else realizing it, so it seems like a good idea to me.

-Christoffer