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OA reports in the OA buffer contain an OA timestamp field that helps user calculate delta between 2 OA reports. The calculation relies on the CS timestamp frequency to convert the timestamp value to nanoseconds. The CS timestamp frequency is a function of the CTC_SHIFT value in RPM_CONFIG0. In DG2, OA unit assumes that the CTC_SHIFT is 3, instead of using the actual value from RPM_CONFIG0. At the user level, this results in an error in calculating delta between 2 OA reports since the OA timestamp is not shifted in the same manner as CS timestamp. Also the periodicity of the reports is different from what the user configured because of mismatch in the CS and OA frequencies. The issue also affects MI_REPORT_PERF_COUNT command. To resolve this, return actual OA timestamp frequency to the user in i915_getparam_ioctl, so that user can calculate the right OA exponent as well as interpret the reports correctly. MR: https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/18893 v2: - Use REG_FIELD_GET (Ashutosh) - Update commit msg Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com> Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com> Signed-off-by: John Harrison <John.C.Harrison@Intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20221026222102.5526-13-umesh.nerlige.ramappa@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.