On 15/10/2025 14:00, Boris Brezillon wrote: > From: Loïc Molinari <[email protected]> > > Will be used by the UMD to optimize CPU accesses to buffers > that are frequently read by the CPU, or on which the access > pattern makes non-cacheable mappings inefficient. > > Mapping buffers CPU-cached implies taking care of the CPU > cache maintenance in the UMD, unless the GPU is IO coherent. > > v2: > - Add more to the commit message > - Tweak the doc > - Make sure we sync the section of the BO pointing to the CS > syncobj before we read its seqno > > v3: > - Fix formatting/spelling issues > > Signed-off-by: Loïc Molinari <[email protected]> > Signed-off-by: Boris Brezillon <[email protected]>
Reviewed-by: Steven Price <[email protected]> > --- > drivers/gpu/drm/panthor/panthor_drv.c | 7 ++++++- > drivers/gpu/drm/panthor/panthor_gem.c | 3 +++ > drivers/gpu/drm/panthor/panthor_sched.c | 18 ++++++++++++++++-- > include/uapi/drm/panthor_drm.h | 9 +++++++++ > 4 files changed, 34 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/panthor/panthor_drv.c > b/drivers/gpu/drm/panthor/panthor_drv.c > index 9004d0ba0e45..d2c321404a75 100644 > --- a/drivers/gpu/drm/panthor/panthor_drv.c > +++ b/drivers/gpu/drm/panthor/panthor_drv.c > @@ -900,7 +900,8 @@ static int panthor_ioctl_vm_destroy(struct drm_device > *ddev, void *data, > return panthor_vm_pool_destroy_vm(pfile->vms, args->id); > } > > -#define PANTHOR_BO_FLAGS DRM_PANTHOR_BO_NO_MMAP > +#define PANTHOR_BO_FLAGS (DRM_PANTHOR_BO_NO_MMAP | \ > + DRM_PANTHOR_BO_WB_MMAP) > > static int panthor_ioctl_bo_create(struct drm_device *ddev, void *data, > struct drm_file *file) > @@ -919,6 +920,10 @@ static int panthor_ioctl_bo_create(struct drm_device > *ddev, void *data, > goto out_dev_exit; > } > > + if ((args->flags & DRM_PANTHOR_BO_NO_MMAP) && > + (args->flags & DRM_PANTHOR_BO_WB_MMAP)) > + return -EINVAL; > + > if (args->exclusive_vm_id) { > vm = panthor_vm_pool_get_vm(pfile->vms, args->exclusive_vm_id); > if (!vm) { > diff --git a/drivers/gpu/drm/panthor/panthor_gem.c > b/drivers/gpu/drm/panthor/panthor_gem.c > index 617e04134d30..a0ccc316e375 100644 > --- a/drivers/gpu/drm/panthor/panthor_gem.c > +++ b/drivers/gpu/drm/panthor/panthor_gem.c > @@ -280,6 +280,9 @@ panthor_gem_create_with_handle(struct drm_file *file, > bo = to_panthor_bo(&shmem->base); > bo->flags = flags; > > + if (flags & DRM_PANTHOR_BO_WB_MMAP) > + shmem->map_wc = false; > + > if (exclusive_vm) { > bo->exclusive_vm_root_gem = panthor_vm_root_gem(exclusive_vm); > drm_gem_object_get(bo->exclusive_vm_root_gem); > diff --git a/drivers/gpu/drm/panthor/panthor_sched.c > b/drivers/gpu/drm/panthor/panthor_sched.c > index f5e01cb16cfc..a17427cabf2a 100644 > --- a/drivers/gpu/drm/panthor/panthor_sched.c > +++ b/drivers/gpu/drm/panthor/panthor_sched.c > @@ -868,8 +868,11 @@ panthor_queue_get_syncwait_obj(struct panthor_group > *group, struct panthor_queue > struct iosys_map map; > int ret; > > - if (queue->syncwait.kmap) > - return queue->syncwait.kmap + queue->syncwait.offset; > + if (queue->syncwait.kmap) { > + bo = container_of(queue->syncwait.obj, > + struct panthor_gem_object, base.base); > + goto out_sync; > + } > > bo = panthor_vm_get_bo_for_va(group->vm, > queue->syncwait.gpu_va, > @@ -886,6 +889,17 @@ panthor_queue_get_syncwait_obj(struct panthor_group > *group, struct panthor_queue > if (drm_WARN_ON(&ptdev->base, !queue->syncwait.kmap)) > goto err_put_syncwait_obj; > > +out_sync: > + /* Make sure the CPU caches are invalidated before the seqno is read. > + * drm_gem_shmem_sync() is a NOP if map_wc=false, so no need to check > + * it here. > + */ > + drm_gem_shmem_sync(&bo->base, queue->syncwait.offset, > + queue->syncwait.sync64 ? > + sizeof(struct panthor_syncobj_64b) : > + sizeof(struct panthor_syncobj_32b), > + DRM_GEM_OBJECT_CPU_ACCESS | > DRM_GEM_OBJECT_READ_ACCESS); > + > return queue->syncwait.kmap + queue->syncwait.offset; > > err_put_syncwait_obj: > diff --git a/include/uapi/drm/panthor_drm.h b/include/uapi/drm/panthor_drm.h > index 63ea44ab961d..dca162781bb2 100644 > --- a/include/uapi/drm/panthor_drm.h > +++ b/include/uapi/drm/panthor_drm.h > @@ -681,6 +681,15 @@ struct drm_panthor_vm_get_state { > enum drm_panthor_bo_flags { > /** @DRM_PANTHOR_BO_NO_MMAP: The buffer object will never be CPU-mapped > in userspace. */ > DRM_PANTHOR_BO_NO_MMAP = (1 << 0), > + > + /** > + * @DRM_PANTHOR_BO_WB_MMAP: Force "Write-Back Cacheable" CPU mapping. > + * > + * CPU map the buffer object in userspace by forcing the "Write-Back > + * Cacheable" cacheability attribute. The mapping otherwise uses the > + * "Non-Cacheable" attribute if the GPU is not IO coherent. > + */ > + DRM_PANTHOR_BO_WB_MMAP = (1 << 1), > }; > > /**
