metag: perf: fixes for interrupting perf counters
metag: perf: fixes for interrupting perf counters

The overflow handler needs to read modify write when re-enabling the
counter so as not to change the counter value as it may have been
changed to ready the next interrupt on overflow. Similarly for
interrupting counters metag_pmu_enable_counter needs to leave the
counter value unchanged rather than resetting it to zero.

Signed-off-by: James Hogan <547fa85bb3888a0222eed8ec39e36708605c6d53@imgtec.com>
Cc: Peter Zijlstra <645ca7d3a8d3d4f60557176cd361ea8351edc32b@chello.nl>
Cc: Paul Mackerras <19a0ba370c443ba08d20b5061586430ab449ee8c@samba.org>
Cc: Ingo Molnar <9dbbbf0688fedc85ad4da37637f1a64b8c718ee2@redhat.com>
Cc: Arnaldo Carvalho de Melo <293abb6b76d7791c0732cc517d38c4b5c734b87f@ghostprotocols.net>

KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs