[Intel-xe] [PATCH v2 6/7] drm/xe/mocs: LNCF MOCS settings only need to be restored on pre-Xe_HP

[Lucas De Marchi]

On Thu, Feb 23, 2023 at 10:57:39AM -0800, Matt Roper wrote:
>Reprogramming the LNCF MOCS registers on render domain reset is not
>intended to be regular driver programming, but rather the implementation
>of a specific workaround (Wa_1607983814).  This workaround no longer
>applies on Xe_HP any beyond, so we can expect that these registers, like
>the rest of the LNCF/LBCF registers, will maintain their values through
>all engine resets.  We should only add these registers to the GuC's
>save/restore list on platforms that need the workaround.
>
>Furthermore, xe_mocs_init_engine() appears to be another attempt to
>satisfy this same workaround.  This is unnecessary on the Xe driver
>since even on platforms where the workaround is necessary, all
>single-engine resets are initiated by the GuC and thus the GuC will take
>care of saving/restoring these registers.  The only host-initiated
>resets we have in Xe are full GT resets which will already
>(re)initialize these registers as part of the regular xe_mocs_init()
>flow.
>
>v2:
> - Add needs_wa_1607983814() so that calculate_regset_size() doesn't
>   overallocate regset space when the workaround isn't needed.  (Lucas)
> - On platforms affected by Wa_1607983814, only add the LNCF MOCS
>   registers to the render engine's GuC save/restore list; resets of
>   other engines don't need to save/restore these.
>
>Cc: Lucas De Marchi <lucas.demarchi at intel.com>
>Signed-off-by: Matt Roper <matthew.d.roper at intel.com>


Reviewed-by: Lucas De Marchi <lucas.demarchi at intel.com>


Lucas De Marchi