On Monday, January 29, 2018 8:21:23 AM CET Viresh Kumar wrote:

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

[ Upstream commit 56026645e2b6f11ede34a5e6ab69d3eb56f9c8fc ]

After commit aa7519af450d (cpufreq: Use transition_delay_us for legacy governors as well) the sampling_rate field of struct dbs_data may be less than the tick period which causes dbs_update() to produce incorrect results, so make the code ensure that the value of that field will always be sufficiently large.

Cc: 4.14 stable@vger.kernel.org # 4.14 Fixes: aa7519af450d (cpufreq: Use transition_delay_us for legacy governors as well) Reported-by: Andy Tang andy.tang@nxp.com Reported-by: Doug Smythies dsmythies@telus.net Tested-by: Andy Tang andy.tang@nxp.com Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Acked-by: Viresh Kumar viresh.kumar@linaro.org

---

drivers/cpufreq/cpufreq_governor.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c index 58d4f4e1ad6a..ca38229b045a 100644 --- a/drivers/cpufreq/cpufreq_governor.c +++ b/drivers/cpufreq/cpufreq_governor.c @@ -22,6 +22,8 @@ #include "cpufreq_governor.h" +#define CPUFREQ_DBS_MIN_SAMPLING_INTERVAL (2 * TICK_NSEC / NSEC_PER_USEC)

static DEFINE_PER_CPU(struct cpu_dbs_info, cpu_dbs); static DEFINE_MUTEX(gov_dbs_data_mutex); @@ -47,11 +49,15 @@ ssize_t store_sampling_rate(struct gov_attr_set *attr_set, const char *buf, { struct dbs_data *dbs_data = to_dbs_data(attr_set); struct policy_dbs_info *policy_dbs;

• unsigned int sampling_interval; int ret;

• ret = sscanf(buf, "%u", &dbs_data->sampling_rate);
• if (ret != 1)

• ret = sscanf(buf, "%u", &sampling_interval);
• if (ret != 1 || sampling_interval < CPUFREQ_DBS_MIN_SAMPLING_INTERVAL) return -EINVAL;

• dbs_data->sampling_rate = sampling_interval;
• /*
  • We are operating under dbs_data->mutex and so the list and its
  • entries can't be freed concurrently.

@@ -430,7 +436,14 @@ int cpufreq_dbs_governor_init(struct cpufreq_policy *policy) if (ret) goto free_policy_dbs_info;

• dbs_data->sampling_rate = cpufreq_policy_transition_delay_us(policy);

• /*

• * The sampling interval should not be less than the transition latency
  

• * of the CPU and it also cannot be too small for dbs_update() to work
  

• * correctly.
  

• */
  

• dbs_data->sampling_rate = max_t(unsigned int,

• 			CPUFREQ_DBS_MIN_SAMPLING_INTERVAL,
  

• 			cpufreq_policy_transition_delay_us(policy));
  

if (!have_governor_per_policy()) gov->gdbs_data = dbs_data;

Right, thanks for pushing this to -stable!