BMC/Intel-BMC/linux.git/drivers/cpufreq/intel_pstate.c, branch dev-4.6

intel_pstate: Fix intel_pstate_get()

2016-05-04T12:09:16+00:00

After commit 8fa520af5081 "intel_pstate: Remove freq calculation from intel_pstate_calc_busy()" intel_pstate_get() calls get_avg_frequency() to compute the average frequency, which is problematic for two reasons. First, intel_pstate_get() may be invoked before the driver reads the CPU feedback registers for the first time and if that happens, get_avg_frequency() will attempt to divide by zero. Second, the get_avg_frequency() call in intel_pstate_get() is racy with respect to intel_pstate_sample() and it may end up returning completely meaningless values for this reason. Moreover, after commit 7349ec0470b6 "intel_pstate: Move intel_pstate_calc_busy() into get_target_pstate_use_performance()" sample.core_pct_busy is never computed on Atom, but it is used in intel_pstate_adjust_busy_pstate() in that case too. To address those problems notice that if sample.core_pct_busy was used in the average frequency computation carried out by get_avg_frequency(), both the divide by zero problem and the race with respect to intel_pstate_sample() would be avoided. Accordingly, move the invocation of intel_pstate_calc_busy() from get_target_pstate_use_performance() to intel_pstate_update_util(), which also will take care of the uninitialized sample.core_pct_busy on Atom, and modify get_avg_frequency() to use sample.core_pct_busy as per the above. Reported-by: kernel test robot Link: http://marc.info/?l=linux-kernel&m=146226437623173&w=4 Fixes: 8fa520af5081 "intel_pstate: Remove freq calculation from intel_pstate_calc_busy()" Fixes: 7349ec0470b6 "intel_pstate: Move intel_pstate_calc_busy() into get_target_pstate_use_performance()" Signed-off-by: Rafael J. Wysocki

cpufreq: intel_pstate: Fix HWP on boot CPU after system resume

2016-05-02T11:48:15+00:00

Commit 41cfd64cf49fc "Update frequencies of policy->cpus only from ->set_policy()" changed the way the intel_pstate driver's ->set_policy callback updates the HWP (hardware-managed P-states) settings. A side effect of it is that if those settings are modified on the boot CPU during system suspend and wakeup, they will never be restored during subsequent system resume. To address this problem, allow cpufreq drivers that don't provide ->target or ->target_index callbacks to use ->suspend and ->resume callbacks and add a ->resume callback to intel_pstate to restore the HWP settings on the CPUs that belong to the given policy. Fixes: 41cfd64cf49fc "Update frequencies of policy->cpus only from ->set_policy()" Tested-by: Srinivas Pandruvada Signed-off-by: Rafael J. Wysocki Acked-by: Viresh Kumar

cpufreq: intel_pstate: Fix processing for turbo activation ratio

2016-04-25T21:39:09+00:00

When the config TDP level is not nominal (level = 0), the MSR values for reading level 1 and level 2 ratios contain power in low 14 bits and actual ratio bits are at bits [23:16]. The current processing for level 1 and level 2 is wrong as there is no shift done to get actual ratio. Fixes: 6a35fc2d6c22 (cpufreq: intel_pstate: get P1 from TAR when available) Signed-off-by: Srinivas Pandruvada Cc: 4.4+ # 4.4+ Signed-off-by: Rafael J. Wysocki

intel_pstate: Avoid getting stuck in high P-states when idle

2016-04-10T03:59:10+00:00

Jörg Otte reports that commit a4675fbc4a7a (cpufreq: intel_pstate: Replace timers with utilization update callbacks) caused the CPUs in his Haswell-based system to stay in the very high frequency region even if the system is completely idle. That turns out to be an existing problem in the intel_pstate driver's P-state selection algorithm for Core processors. Namely, all decisions made by that algorithm are based on the average frequency of the CPU between sampling events and on the P-state requested on the last invocation, so it may get stuck at a very hight frequency even if the utilization of the CPU is very low (in fact, it may get stuck in a inadequate P-state regardless of the CPU utilization). The only way to kick it out of that limbo is a sufficiently long idle period (3 times longer than the prescribed sampling interval), but if that doesn't happen often enough (eg. due to a timing change like after the above commit), the P-state of the CPU may be inadequate pretty much all the time. To address the most egregious manifestations of that issue, reset the core_busy value used to determine the next P-state to request if the utilization of the CPU, determined with the help of the MPERF feedback register and the TSC, is below 1%. Link: https://bugzilla.kernel.org/show_bug.cgi?id=115771 Reported-and-tested-by: Jörg Otte Signed-off-by: Rafael J. Wysocki

cpufreq: intel_pstate: Documenation for structures

2016-04-05T01:39:05+00:00

No code change. Only added kernel doc style comments for structures. Signed-off-by: Srinivas Pandruvada Signed-off-by: Rafael J. Wysocki

cpufreq: intel_pstate: fix inconsistency in setting policy limits

2016-04-05T01:37:13+00:00

When user sets performance policy using cpufreq interface, it is possible that because of policy->max limits, the actual performance is still limited. But the current implementation will silently switch the policy to powersave and start using powersave limits. If user modifies any limits using intel_pstate sysfs, this is actually changing powersave limits. The current implementation tracks limits under powersave and performance policy using two different variables. When policy->max is less than policy->cpuinfo.max_freq, only powersave limit variable is used. This fix causes the performance limits variable to be used always when the policy is performance. Signed-off-by: Srinivas Pandruvada Signed-off-by: Rafael J. Wysocki

intel_pstate: Avoid extra invocation of intel_pstate_sample()

2016-04-01T23:06:21+00:00

The initialization of intel_pstate for a given CPU involves populating the fields of its struct cpudata that represent the previous sample, but currently that is done in a problematic way. Namely, intel_pstate_init_cpu() makes an extra call to intel_pstate_sample() so it reads the current register values that will be used to populate the "previous sample" record during the next invocation of intel_pstate_sample(). However, after commit a4675fbc4a7a (cpufreq: intel_pstate: Replace timers with utilization update callbacks) that doesn't work for last_sample_time, because the time value is passed to intel_pstate_sample() as an argument now. Passing 0 to it from intel_pstate_init_cpu() is problematic, because that causes cpu->last_sample_time == 0 to be visible in get_target_pstate_use_performance() (and hence the extra cpu->last_sample_time > 0 check in there) and effectively allows the first invocation of intel_pstate_sample() from intel_pstate_update_util() to happen immediately after the initialization which may lead to a significant "turn on" effect in the governor algorithm. To mitigate that issue, rework the initialization to avoid the extra intel_pstate_sample() call from intel_pstate_init_cpu(). Instead, make intel_pstate_sample() return false if it has been called with cpu->sample.time equal to zero, which will make intel_pstate_update_util() skip the sample in that case, and reset cpu->sample.time from intel_pstate_set_update_util_hook() to make the algorithm start properly every time the hook is set. Signed-off-by: Rafael J. Wysocki

intel_pstate: Do not set utilization update hook too early

2016-03-31T15:42:15+00:00

The utilization update hook in the intel_pstate driver is set too early, as it only should be set after the policy has been fully initialized by the core. That may cause intel_pstate_update_util() to use incorrect data and put the CPUs into incorrect P-states as a result. To prevent that from happening, make intel_pstate_set_policy() set the utilization update hook instead of intel_pstate_init_cpu() so intel_pstate_update_util() only runs when all things have been initialized as appropriate. Signed-off-by: Rafael J. Wysocki

intel_pstate: Do not call wrmsrl_on_cpu() with disabled interrupts

2016-03-19T23:37:09+00:00

After commit a4675fbc4a7a (cpufreq: intel_pstate: Replace timers with utilization update callbacks) wrmsrl_on_cpu() cannot be called in the intel_pstate_adjust_busy_pstate() path as that is executed with disabled interrupts. However, atom_set_pstate() called from there via intel_pstate_set_pstate() uses wrmsrl_on_cpu() to update the IA32_PERF_CTL MSR which triggers the WARN_ON_ONCE() in smp_call_function_single(). The reason why wrmsrl_on_cpu() is used by atom_set_pstate() is because intel_pstate_set_pstate() calling it is also invoked during the initialization and cleanup of the driver and in those cases it is not guaranteed to be run on the CPU that is being updated. However, in the case when intel_pstate_set_pstate() is called by intel_pstate_adjust_busy_pstate(), wrmsrl() can be used to update the register safely. Moreover, intel_pstate_set_pstate() already contains code that only is executed if the function is called by intel_pstate_adjust_busy_pstate() and there is a special argument passed to it because of that. To fix the problem at hand, rearrange the code taking the above observations into account. First, replace the ->set() callback in struct pstate_funcs with a ->get_val() one that will return the value to be written to the IA32_PERF_CTL MSR without updating the register. Second, split intel_pstate_set_pstate() into two functions, intel_pstate_update_pstate() to be called by intel_pstate_adjust_busy_pstate() that will contain all of the intel_pstate_set_pstate() code which only needs to be executed in that case and will use wrmsrl() to update the MSR (after obtaining the value to write to it from the ->get_val() callback), and intel_pstate_set_min_pstate() to be invoked during the initialization and cleanup that will set the P-state to the minimum one and will update the MSR using wrmsrl_on_cpu(). Finally, move the code shared between intel_pstate_update_pstate() and intel_pstate_set_min_pstate() to a new static inline function intel_pstate_record_pstate() and make them both call it. Of course, that unifies the handling of the IA32_PERF_CTL MSR writes between Atom and Core. Fixes: a4675fbc4a7a (cpufreq: intel_pstate: Replace timers with utilization update callbacks) Reported-and-tested-by: Josh Boyer Signed-off-by: Rafael J. Wysocki

intel_pstate: Do not skip samples partially

2016-03-10T23:07:51+00:00

If the current value of MPERF or the current value of TSC is the same as the previous one, respectively, intel_pstate_sample() bails out early and skips the sample. However, intel_pstate_adjust_busy_pstate() is still called in that case which is not correct, so modify intel_pstate_sample() to return a bool value indicating whether or not the sample has been taken and use it to decide whether or not to call intel_pstate_adjust_busy_pstate(). While at it, remove redundant parentheses from the MPERF/TSC check in intel_pstate_sample(). Signed-off-by: Rafael J. Wysocki Acked-by: Srinivas Pandruvada