[PATCH 4.18 017/350] cpufreq: conservative: Take limits changes into account properly

Greg Kroah-Hartman
2018-11-11T22:29:43Z

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

commit da5e79bc70b84971d2b3a55fb252e34e51d81d48 upstream.

If the policy limits change between invocations of cs_dbs_update(),
the requested frequency value stored in dbs_info may not be updated
and the function may use a stale value of it next time. Moreover, if
idle periods are takem into account by cs_dbs_update(), the requested
frequency value stored in dbs_info may be below the min policy limit,
which is incorrect.

To fix these problems, always update the requested frequency value
in dbs_info along with the local copy of it when the previous
requested frequency is beyond the policy limits and avoid decreasing
the requested frequency below the min policy limit when taking
idle periods into account.

Fixes: abb6627910a1 (cpufreq: conservative: Fix next frequency selection)
Fixes: 00bfe05889e9 (cpufreq: conservative: Decrease frequency faster for deferred updates)
Reported-by: Waldemar Rymarkiewicz <waldemarx.rymarkiewicz@intel.com>
Cc: All applicable <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Waldemar Rymarkiewicz <waldemarx.rymarkiewicz@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/cpufreq/cpufreq_conservative.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/cpufreq/cpufreq_conservative.c
+++ b/drivers/cpufreq/cpufreq_conservative.c
@@ -80,8 +80,10 @@ static unsigned int cs_dbs_update(struct
* changed in the meantime, so fall back to current frequency in that
* case.
*/
- if (requested_freq > policy->max || requested_freq < policy->min)
+ if (requested_freq > policy->max || requested_freq < policy->min) {
requested_freq = policy->cur;
+ dbs_info->requested_freq = requested_freq;
+ }

freq_step = get_freq_step(cs_tuners, policy);

@@ -92,7 +94,7 @@ static unsigned int cs_dbs_update(struct
if (policy_dbs->idle_periods < UINT_MAX) {
unsigned int freq_steps = policy_dbs->idle_periods * freq_step;

- if (requested_freq > freq_steps)
+ if (requested_freq > policy->min + freq_steps)
requested_freq -= freq_steps;
else
requested_freq = policy->min;