perf_counter: powerpc: Enable use of software counters on 32-bit powerpc

This enables the perf_counter subsystem on 32-bit powerpc.  Since we
don't have any support for hardware counters on 32-bit powerpc yet,
only software counters can be used.

Besides selecting HAVE_PERF_COUNTERS for 32-bit powerpc as well as
64-bit, the main thing this does is add an implementation of
set_perf_counter_pending().  This needs to arrange for
perf_counter_do_pending() to be called when interrupts are enabled.
Rather than add code to local_irq_restore as 64-bit does, the 32-bit
set_perf_counter_pending() generates an interrupt by setting the
decrementer to 1 so that a decrementer interrupt will become pending
in 1 or 2 timebase ticks (if a decrementer interrupt isn't already
pending).  When interrupts are enabled, timer_interrupt() will be
called, and some new code in there calls perf_counter_do_pending().
We use a per-cpu array of flags to indicate whether we need to call
perf_counter_do_pending() or not.

This introduces a couple of new Kconfig symbols: PPC_HAVE_PMU_SUPPORT,
which is selected by processor families for which we have hardware PMU
support (currently only PPC64), and PPC_PERF_CTRS, which enables the
powerpc-specific perf_counter back-end.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: linuxppc-dev@ozlabs.org
Cc: benh@kernel.crashing.org
LKML-Reference: <19000.55404.103840.393470@cargo.ozlabs.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 10 insertions, 1 deletions

diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
index cca6b4fc719a..dd9f3ec5ee30 100644
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype
@@ -1,7 +1,7 @@
 config PPC64
         bool "64-bit kernel"
         default n
-        select HAVE_PERF_COUNTERS
+        select PPC_HAVE_PMU_SUPPORT
         help
           This option selects whether a 32-bit or a 64-bit kernel
           will be built.
@@ -243,6 +243,15 @@ config VIRT_CPU_ACCOUNTING
 
           If in doubt, say Y here.
 
+config PPC_HAVE_PMU_SUPPORT
+       bool
+
+config PPC_PERF_CTRS
+       def_bool y
+       depends on PERF_COUNTERS && PPC_HAVE_PMU_SUPPORT
+       help
+         This enables the powerpc-specific perf_counter back-end.
+
 config SMP
         depends on PPC_STD_MMU || FSL_BOOKE
         bool "Symmetric multi-processing support"