On 03/12/2014 04:30 PM, Rafael J. Wysocki wrote:
Dirk, please let me know if you're fine with it.
---
From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Subject: cpufreq: Skip current frequency initialization for ->setpolicy drivers
After commit da60ce9f2fac (cpufreq: call cpufreq_driver->get() after
calling ->init()) __cpufreq_add_dev() sometimes fails for CPUs handled
by intel_pstate, because that driver may return 0 from its ->get()
callback if it has not run long enough to collect enough samples on the
given CPU. That didn't happen before commit da60ce9f2fac which added
policy->cur initialization to __cpufreq_add_dev() to help reduce code
duplication in other cpufreq drivers.
However, the code added by commit da60ce9f2fac need not be executed
for cpufreq drivers having the ->setpolicy callback defined, because
the subsequent invocation of cpufreq_set_policy() will use that
callback to initialize the policy anyway and it doesn't need
policy->cur to be initialized upfront. The analogous code in
cpufreq_update_policy() is also unnecessary for cpufreq drivers
having ->setpolicy set and may be skipped for them as well.
Since intel_pstate provides ->setpolicy, skipping the upfront
policy->cur initialization for cpufreq drivers with that callback
set will cover intel_pstate and the problem it's been having after
commit da60ce9f2fac will be addressed.
Fixes: da60ce9f2fac (cpufreq: call cpufreq_driver->get() after calling ->init())
References: https://bugzilla.kernel.org/show_bug.cgi?id=71931
Reported-and-tested-by: Patrik Lundquist <patrik.lundquist@xxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Acked-by: Dirk Brandewie <dirk.j.brandewie@xxxxxxxxx>
Cc: 3.13+ <stable@xxxxxxxxxxxxxxx> # 3.13+
---
drivers/cpufreq/cpufreq.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
Index: linux-pm/drivers/cpufreq/cpufreq.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/cpufreq.c
+++ linux-pm/drivers/cpufreq/cpufreq.c
@@ -1129,7 +1129,7 @@ static int __cpufreq_add_dev(struct devi
per_cpu(cpufreq_cpu_data, j) = policy;
write_unlock_irqrestore(&cpufreq_driver_lock, flags);
- if (cpufreq_driver->get) {
+ if (cpufreq_driver->get && !cpufreq_driver->setpolicy) {
policy->cur = cpufreq_driver->get(policy->cpu);
if (!policy->cur) {
pr_err("%s: ->get() failed\n", __func__);
@@ -2143,7 +2143,7 @@ int cpufreq_update_policy(unsigned int c
* BIOS might change freq behind our back
* -> ask driver for current freq and notify governors about a change
*/
- if (cpufreq_driver->get) {
+ if (cpufreq_driver->get && !cpufreq_driver->setpolicy) {
new_policy.cur = cpufreq_driver->get(cpu);
if (!policy->cur) {
pr_debug("Driver did not initialize current freq");
--
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