Hi Thomas,
Le lun. 8 mars 2021 à 9:41, Thomas Zimmermann <tzimmermann@xxxxxxx> a
écrit :
Hi Paul,
having individual functions for each mode only makes sense if the
decision is at compile time. But in patch 5, you're working around
your earlier design by introducing in-driver helpers that select the
correct CMA function.
In SHMEM helpers we have the flag map_wc in the GEM structure that
selects the pages caching mode (wc vs uncached). I think CMA should
use this design as well. Have a map_noncoherent flag in the CMA GEM
object and set it from the driver's implementation of
gem_create_object.
Is that a new addition? That severely reduces the patchset size, which
is perfect.
I'll send a V3 then.
Cheers,
-Paul
And in the long run, we could try to consolidate all drivers/helpers
mapping flags in struct drm_gem_object.
Best regards
Thomas
Am 07.03.21 um 21:28 schrieb Paul Cercueil:
Rework of my previous patchset which added support for GEM buffers
backed by non-coherent memory to the ingenic-drm driver.
Having GEM buffers backed by non-coherent memory is interesting in
the particular case where it is faster to render to a non-coherent
buffer then sync the data cache, than to render to a write-combine
buffer, and (by extension) much faster than using a shadow buffer.
This is true for instance on some Ingenic SoCs, where even simple
blits (e.g. memcpy) are about three times faster using this method.
For the record, the previous patchset was accepted for 5.10 then had
to be reverted, as it conflicted with some changes made to the DMA
API.
This new patchset is pretty different as it adds the functionality to
the DRM core. The first three patches add variants to existing
functions
but with the "non-coherent memory" twist, exported as GPL symbols.
The
fourth patch adds a function to be used with the damage helpers.
Finally, the last patch adds support for non-coherent GEM buffers to
the
ingenic-drm driver. The functionality is enabled through a module
parameter, and is disabled by default.
Cheers,
-Paul
Paul Cercueil (5):
drm: Add and export function drm_gem_cma_create_noncoherent
drm: Add and export function drm_gem_cma_dumb_create_noncoherent
drm: Add and export function drm_gem_cma_mmap_noncoherent
drm: Add and export function drm_gem_cma_sync_data
drm/ingenic: Add option to alloc cached GEM buffers
drivers/gpu/drm/drm_gem_cma_helper.c | 223
+++++++++++++++++++---
drivers/gpu/drm/ingenic/ingenic-drm-drv.c | 49 ++++-
drivers/gpu/drm/ingenic/ingenic-drm.h | 4 +
drivers/gpu/drm/ingenic/ingenic-ipu.c | 14 +-
include/drm/drm_gem_cma_helper.h | 13 ++
5 files changed, 273 insertions(+), 30 deletions(-)
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer
