cpu_to_chip_id() does a DT walk through to find out the chip id by taking a
contended device tree lock. This adds an unnecessary overhead in a hot-path.
So instead of cpu_to_chip_id() use PIR of the cpu to find the chip id.
Reported-by: Anton Blanchard <an...@samba.org>
Signed-off-by: Shilpasri G Bhat <shilpa.b...@linux.vnet.ibm.com>
---
drivers/cpufreq/powernv-cpufreq.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/drivers/cpufreq/powernv-cpufreq.c
b/drivers/cpufreq/powernv-cpufreq.c
index cb50138..597a084 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c
@@ -39,6 +39,7 @@
#define PMSR_PSAFE_ENABLE (1UL << 30)
#define PMSR_SPR_EM_DISABLE (1UL << 31)
#define PMSR_MAX(x) ((x >> 32) & 0xFF)
+#define pir_to_chip_id(pir) (((pir) >> 7) & 0x3f)
static struct cpufreq_frequency_table powernv_freqs[POWERNV_MAX_PSTATES+1];
static bool rebooting, throttled, occ_reset;
@@ -312,13 +313,14 @@ static inline unsigned int get_nominal_index(void)
static void powernv_cpufreq_throttle_check(void *data)
{
unsigned int cpu = smp_processor_id();
+ unsigned int chip_id = pir_to_chip_id(hard_smp_processor_id());
unsigned long pmsr;
int pmsr_pmax, i;
pmsr = get_pmspr(SPRN_PMSR);
for (i = 0; i < nr_chips; i++)
- if (chips[i].id == cpu_to_chip_id(cpu))
+ if (chips[i].id == chip_id)
break;
/* Check for Pmax Capping */
@@ -558,7 +560,8 @@ static int init_chip_info(void)
unsigned int prev_chip_id = UINT_MAX;
for_each_possible_cpu(cpu) {
- unsigned int id = cpu_to_chip_id(cpu);
+ unsigned int id =
+ pir_to_chip_id(get_hard_smp_processor_id(cpu));
if (prev_chip_id != id) {
prev_chip_id = id;
--
1.9.1
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