mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-05-02 10:59:18 -04:00
3f8ed54aee
In the functions intel_pstate_hwp_set(), min/max range from HWP capability MSR along with max_perf_pct and min_perf_pct, is used to set the HWP request MSR. In some cases this doesn't result in the correct HWP max/min in HWP request. For example: In the following case: HWP capabilities from MSR 0x771 0x70a1220 Here cpufreq min/max frequencies from above MSR dump are 700MHz and 3.2GHz respectively. This will result in hwp_min = 0x07 hwp_max = 0x20 To limit max frequency to 2GHz: perf_limits->max_perf_pct = 63 (2GHz as a percent of 3.2GHz rounded up) With the current calculation: adj_range = max_perf_pct * range / 100; adj_range = 63 * (32 - 7) / 100 adj_range = 15 max = hw_min + adj_range; max = 7 + 15 = 22 This will result in HWP request of 0x160f, which will result in a frequency cap of 2.2GHz not 2GHz. The problem with the above calculation is that hwp_min of 7 is treated as 0% in the range. But max_perf_pct is calculated with respect to minimum as 0 and max as 3.2GHz or hwp_max, so adding hwp_min to it will result in more than the desired. Since the min_perf_pct and max_perf_pct is already a percent of max frequency or hwp_max, this min/max HWP request value can be calculated directly applying these percentage to hwp_max. Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.