On 23/02/2022 12:08, Balasubramani Vivekanandan wrote:
On 23.02.2022 10:02, Das, Nirmoy wrote:
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?
I have changed all users of i915_memcpy_from_wc() to drm function. But
this is another function i915_unaligned_memcpy_from_wc() in
i915_memcpy.c which is blocking completely eliminating the i915_memcpy.c
file from i915.
This function accepts unaligned source address and does fast copy only
for the aligned region of memory and remaining part is copied using
memcpy function.
Either I can move i915_unaligned_memcpy_from_wc() also to drm but I am
concerned since it is more a platform specific handling, does it make
sense to keep it in drm.
Else I have retain to i915_unaligned_memcpy_from_wc() inside i915 and
refactor the function to use drm_memcpy_from_wc() instead of the
__memcpy_ntdqu().
I think for completeness it makes sense to remove i915_memcpy_from_wc()
and its helper functions
in this series. I don't think we can have
i915_unaligned_memcpy_from_wc() if want i915 on ARM[0] so I think
you can remove usages of i915_unaligned_memcpy_from_wc() as well.
[0]IIUC CI_BUG_ON() check in i915_unaligned_memcpy_from_wc() will
raise a build error on ARM
Regards,
Nirmoy
But before I could do more changes, I wanted feedback on the current
change. So I decided to go ahead with creating series for review.
Regards,
Bala
Regards,
Nirmoy
Cc: Jani Nikula <jani.nikula@xxxxxxxxx>
Cc: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
Cc: David Airlie <airlied@xxxxxxxx>
Cc: Daniel Vetter <daniel@xxxxxxxx>
Cc: Chris Wilson <chris.p.wilson@xxxxxxxxx>
Cc: Thomas Hellstr_m <thomas.hellstrom@xxxxxxxxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>
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(-)
