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    SubjectRe: [PATCH v2 0/5] Add option to mmap GEM buffers cached
    Hi Thomas,

    Le lun. 8 mars 2021 à 9:41, Thomas Zimmermann <tzimmermann@suse.de> 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
    >


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