bcdcae6327
Using system memory for the DSB command buffer doesn't appear to work. On DG2 it seems like the hardware internally replaces the actual memory reads with zeroes, and so we end up executing a bunch of NOOPs instead of whatever commands we put in the buffer. To determine that I measured the time it takes to execute the instructions, and the results are always more or less consistent with executing a buffer full of NOOPs from local memory. Another theory I considered was some kind of cache coherency issue. Looks like i915_gem_object_pin_map_unlocked() will in fact give you a WB mapping for system memory on DGFX regardless of what mapping mode was requested (WC in case of the DSB code). But clflush did not change the behaviour at all, so that theory seems moot. On DG1 it looks like the hardware might actually be fetching data from system memory as the logs indicate that we just get underruns. But that is equally bad, so doesn't look like we can really use system memory on DG1 either. Thus always allocate the DSB command buffer from local memory on discrete GPUs. Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20231009132204.15098-1-ville.syrjala@linux.intel.com Reviewed-by: Uma Shankar <uma.shankar@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.