On Wed, Aug 27, 2014 at 3:26 PM, Stephen Boyd [off-list ref] wrote:

+Mark (author of change in question)

On 08/27/14 14:27, Sonny Rao wrote:

quoted

On Wed, Aug 27, 2014 at 2:19 PM, Olof Johansson [off-list ref] wrote:

quoted

On Wed, Aug 27, 2014 at 2:03 PM, Sonny Rao [off-list ref] wrote:

quoted

This is a bug fix for using physical arch timers when
the arch_timer_use_virtual boolean is false.  It restores the
arch_counter_get_cntpct() function after removal in

0d651e4e "clocksource: arch_timer: use virtual counters"

and completes the implementation of memory mapped access for physical
timers, so if a system is trying to use physical timers, it will
function properly.

Signed-off-by: Sonny Rao <redacted>

Acked-by: Olof Johansson <redacted>

This should have a:

Fixes: 0d651e4e65e9 ("clocksource: arch_timer: use virtual counters")

tag too, and possibly cc stable?

Ok, as far as stable goes, this patch wouldn't apply cleanly going all
the way back to  0d651e4e65e9
As-is, it would need to go after 220069945b29 "clocksource:
arch_timer: Add support for memory mapped timers" and there would need
to be another, simpler, version that went between those two commits.

So, I'm not sure what to do in this situation regarding stable?

Greg tends to make a best-effort, you'll find out when he looks at
backporting and can reply with a "punt" or "here's the right patch"
then.

Is there any reason why the virtual counter can't be read? Maybe we're
the hyp and we need to make sure we don't use the virtual timer so that
the guest can use it, but that doesn't have any effect on the usage of
the virtual counter for the clocksource.

There are several cases where virtual is unusable -- in particular it
might not have been configured properly (i.e. the phys/virt offset is
at a bad value).


-Olof