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Chris Wilson
8391c9b28c
We assume that both timestamps are driven off the same clock [reported to userspace as I915_PARAM_CS_TIMESTAMP_FREQUENCY]. Verify that this is so by reading the timestamp registers around a busywait (on an otherwise idle engine so there should be no preemptions). v2: Icelake (not ehl, nor tgl) seems to be using a fixed 80ns interval for, and only for, CTX_TIMESTAMP -- or it may be GPU frequency and the test is always running at maximum frequency?. As far as I can tell, this isolated change in behaviour is undocumented. Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com> Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20201223122359.22562-1-chris@chris-wilson.co.uk
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.