On 2/4/20 3:56 AM, Sergey Senozhatsky wrote: > Hello, > > V2 of the patchset, reshuffled, added more documentation, > addressed some of the feedback ;) Still in RFC, tho > > v1 link: https://lore.kernel.org/lkml/20191217032034.54897-1-senozhatsky@xxxxxxxxxxxx/ > > --- > This is a reworked version of the vb2 cache hints > (V4L2_BUF_FLAG_NO_CACHE_INVALIDATE / V4L2_BUF_FLAG_NO_CACHE_CLEAN) > support patch series which previsouly was developed by Sakari and > Laurent [0]. > > The patch set attempts to preserve the existing behvaiour - cache > sync is performed in ->prepare() and ->finish() (unless the buffer > is DMA exported). User space can request “default behavior” override > with cache management hints, which are handled on a per-buffer basis > and should be supplied with v4l2_buffer ->flags during buffer > preparation. There are two possible hints: > > - V4L2_BUF_FLAG_NO_CACHE_INVALIDATE > No cache sync on ->finish() > > - V4L2_BUF_FLAG_NO_CACHE_CLEAN > No cache sync on ->prepare() > > In order to keep things on the safe side, we also require driver > to explicitly state which of its queues (if any) support user space > cache management hints (such queues should have ->allow_cache_hints > bit set). > > The patch set also (to some extent) simplifies allocators' ->prepare() > and ->finish() callbacks. Namely, we move cache management decision > making to the upper - core - layer. For example, if, previously, we > would have something like this > > vb2_buffer_done() > vb2_dc_finish() > if (buf->db_attach) > return; > > where each allocators' ->finish() callback would either bail > out (DMA exported buffer, for instance) or sync, now that "bail > out or sync" decision is made before we call into the allocator. > > Along with cache management hints, user space is also able to > adjust queue's memory consistency attributes. Memory consistency > attribute (dma_attrs) is per-queue, yet it plays its role on the > allocator level, when we allocate buffers’ private memory (planes). > For the time being, only one consistency attribute is supported: > DMA_ATTR_NON_CONSISTENT. This is starting to look pretty good. I think you can drop the RFC for the next time you post this. One thing I would like to see as well is test code in v4l2-compliance, specifically for testing the various flags and capabilities. I.e., if V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS, then it should test that it can set the cache flags and the NON_CONSISTENT flag. If it is not set, then those flags should be cleared when attempting to set them. Also code in v4l2-ctl and common/v4l2-info.cpp to support the new flags, both reporting them, but also setting them. Regards, Hans > > [0] https://www.mail-archive.com/linux-media@xxxxxxxxxxxxxxx/msg112459.html > > Sergey Senozhatsky (12): > videobuf2: add cache management members > videobuf2: handle V4L2 buffer cache flags > videobuf2: add V4L2_FLAG_MEMORY_NON_CONSISTENT flag > videobuf2: add queue memory consistency parameter > videobuf2: handle V4L2_FLAG_MEMORY_NON_CONSISTENT flag > videobuf2: factor out planes prepare/finish functions > videobuf2: do not sync caches when we are allowed not to > videobuf2: check ->synced flag in prepare() and finish() > videobuf2: let user-space know if driver supports cache hints > videobuf2: add begin/end cpu_access callbacks to dma-contig > videobuf2: add begin/end cpu_access callbacks to dma-sg > videobuf2: don't test db_attach in dma-contig prepare and finish > > Documentation/media/uapi/v4l/buffer.rst | 27 +++++ > .../media/uapi/v4l/vidioc-create-bufs.rst | 9 +- > .../media/uapi/v4l/vidioc-reqbufs.rst | 22 +++- > .../media/common/videobuf2/videobuf2-core.c | 110 +++++++++++++----- > .../common/videobuf2/videobuf2-dma-contig.c | 39 ++++++- > .../media/common/videobuf2/videobuf2-dma-sg.c | 30 +++-- > .../media/common/videobuf2/videobuf2-v4l2.c | 59 +++++++++- > drivers/media/dvb-core/dvb_vb2.c | 2 +- > drivers/media/v4l2-core/v4l2-ioctl.c | 5 +- > include/media/videobuf2-core.h | 17 ++- > include/uapi/linux/videodev2.h | 11 +- > 11 files changed, 273 insertions(+), 58 deletions(-) >
