cpufreq: intel_pstate: Process HWP Guaranteed change notification

cpufreq: intel_pstate: Process HWP Guaranteed change notification

It is possible that HWP guaranteed ratio is changed in response to
change in power and thermal limits. For example when Intel Speed Select
performance profile is changed or there is change in TDP, hardware can
send notifications. It is possible that the guaranteed ratio is
increased. This creates an issue when turbo is disabled, as the old
limits set in MSR_HWP_REQUEST are still lower and hardware will clip
to older limits.

This change enables HWP interrupt and process HWP interrupts. When
guaranteed is changed, calls cpufreq_update_policy() so that driver
callbacks are called to update to new HWP limits. This callback
is called from a delayed workqueue of 10ms to avoid frequent updates.

Although the scope of IA32_HWP_INTERRUPT is per logical cpu, on some
plaforms interrupt is generated on all CPUs. This is particularly a
problem during initialization, when the driver didn't allocated
data for other CPUs. So this change uses a cpumask of enabled CPUs and
process interrupts on those CPUs only.

When the cpufreq offline() or suspend() callback is called, HWP interrupt
is disabled on those CPUs and also cancels any pending work item.

Spin lock is used to protect data and processing shared with interrupt
handler. Here READ_ONCE(), WRITE_ONCE() macros are used to designate
shared data, even though spin lock act as an optimization barrier here.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Tested-by: pablomh@gmail.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>