[Intel-gfx] [PATCH 0/7] drm/i915: Use the memcpy_from_wc function from drm

Das, Nirmoy nirmoy.das at linux.intel.com
Wed Feb 23 09:02:08 UTC 2022

On 22/02/2022 15:51, Balasubramani Vivekanandan wrote:
> drm_memcpy_from_wc() performs fast copy from WC memory type using
> non-temporal instructions. Now there are two similar implementations of
> this function. One exists in drm_cache.c as drm_memcpy_from_wc() and
> another implementation in i915/i915_memcpy.c as i915_memcpy_from_wc().
> drm_memcpy_from_wc() was the recent addition through the series
> https://patchwork.freedesktop.org/patch/436276/?series=90681&rev=6
> The goal of this patch series is to change all users of
> i915_memcpy_from_wc() to drm_memcpy_from_wc() and a have common
> implementation in drm and eventually remove the copy from i915.
> Another benefit of using memcpy functions from drm is that
> drm_memcpy_from_wc() is available for non-x86 architectures.
> i915_memcpy_from_wc() is implemented only for x86 and prevents building
> i915 for ARM64.
> drm_memcpy_from_wc() does fast copy using non-temporal instructions for
> x86 and for other architectures makes use of memcpy() family of
> functions as fallback.
> Another major difference is unlike i915_memcpy_from_wc(),
> drm_memcpy_from_wc() will not fail if the passed address argument is not
> alignment to be used with non-temporal load instructions or if the
> platform lacks support for those instructions (non-temporal load
> instructions are provided through SSE4.1 instruction set extension).
> Instead drm_memcpy_from_wc() continues with fallback functions to
> complete the copy.
> This relieves the caller from checking the return value of
> i915_memcpy_from_wc() and explicitly using a fallback.
> Follow up series will be created to remove the memcpy_from_wc functions
> from i915 once the dependency is completely removed.

Overall the series looks good to me but I think you can add another 
patch to remove

i915_memcpy_from_wc() as I don't see any other usages left after this series, may be I
am missing something?


> Cc: Jani Nikula <jani.nikula at intel.com>
> Cc: Lucas De Marchi <lucas.demarchi at intel.com>
> Cc: David Airlie <airlied at linux.ie>
> Cc: Daniel Vetter <daniel at ffwll.ch>
> Cc: Chris Wilson <chris.p.wilson at intel.com>
> Cc: Thomas Hellstr_m <thomas.hellstrom at linux.intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
> Balasubramani Vivekanandan (7):
>    drm: Relax alignment constraint for destination address
>    drm: Add drm_memcpy_from_wc() variant which accepts destination
>      address
>    drm/i915: use the memcpy_from_wc call from the drm
>    drm/i915/guc: use the memcpy_from_wc call from the drm
>    drm/i915/selftests: use the memcpy_from_wc call from the drm
>    drm/i915/gt: Avoid direct dereferencing of io memory
>    drm/i915: Avoid dereferencing io mapped memory
>   drivers/gpu/drm/drm_cache.c                   | 98 +++++++++++++++++--
>   drivers/gpu/drm/i915/gem/i915_gem_object.c    |  8 +-
>   drivers/gpu/drm/i915/gt/selftest_reset.c      | 21 ++--
>   drivers/gpu/drm/i915/gt/uc/intel_guc_log.c    | 11 ++-
>   drivers/gpu/drm/i915/i915_gpu_error.c         | 45 +++++----
>   .../drm/i915/selftests/intel_memory_region.c  |  8 +-
>   include/drm/drm_cache.h                       |  3 +
>   7 files changed, 148 insertions(+), 46 deletions(-)

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