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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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.