[PATCH 3.12 155/170] intel_pstate: Set CPU number before accessing MSRs

Jiri Slaby
2014-07-18T13:12:17Z

From: Vincent Minet <vincent@vincent-minet.net>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

commit 179e8471673ce0249cd4ecda796008f7757e5bad upstream.

Ensure that cpu->cpu is set before writing MSR_IA32_PERF_CTL during CPU
initialization. Otherwise only cpu0 has its P-state set and all other
cores are left with their values unchanged.

In most cases, this is not too serious because the P-states will be set
correctly when the timer function is run. But when the default governor
is set to performance, the per-CPU current_pstate stays the same forever
and no attempts are made to write the MSRs again.

Signed-off-by: Vincent Minet <vincent@vincent-minet.net>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
drivers/cpufreq/intel_pstate.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index d5dc567efd96..f033fadb58e6 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -550,6 +550,7 @@ static int intel_pstate_init_cpu(unsigned int cpunum)

cpu = all_cpu_data[cpunum];

+ cpu->cpu = cpunum;
intel_pstate_get_cpu_pstates(cpu);
if (!cpu->pstate.current_pstate) {
all_cpu_data[cpunum] = NULL;
@@ -557,7 +558,6 @@ static int intel_pstate_init_cpu(unsigned int cpunum)
return -ENODATA;
}

- cpu->cpu = cpunum;
cpu->pstate_policy =
(struct pstate_adjust_policy *)id->driver_data;
init_timer_deferrable(&cpu->timer);
--
2.0.0