On 12/28/2012 12:49 PM, Matthew Garrett wrote: > On Fri, 2012-12-28 at 12:40 -0800, H. Peter Anvin wrote: > >>> I suspect that what we *should* do looks like: >>> >>> 1. If ACPI exports a Time and Alarm Device (ACPI000E) the use it; >>> 2. If ACPI exports an PC/AT device (PNP0B00/1/2) then use it(*); >>> 3. If we have an EFI RTC use it; >>> 4. Probe for a PC/AT RTC device. > > In terms of ordering, 3 should probably come before 2 - but that depends > on us actually fixing the issues that are preventing some of these calls > from working. As far as wallclock time goes, EFI is going to be > available to us before we've parsed the DSDT to determine whether > there's any ACPI devices, so we'll almost certainly end up having to use > it at at least some point during boot. Otherwise, agreed. > [Resending due to misconfigured tablet] 3 before 2 is exactly what is known to break on existing hardware (ASUS). If anything, we should move to using the EFI RTC as a very last resort, i.e. 3 after 4. Ideally we should match Win8 behavior, but that would require someone mocking up different ACPI and EFI functions in a simulator and see how Win8 prioritizes things. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
