Hi Hans, On Mon, Sep 17, 2018 at 11:41 PM Hans Verkuil <hverk...@xs4all.nl> wrote: > > I'm going through old patches in patchwork that fell through the > cracks, and this is one of them. > > If this is still desired, please rebase and repost. > > I'm marking this series as Obsoleted in patchwork, since it no longer > applies anyway.
The ability to have cached mappings of MMAP buffers is strongly desired, but I'm afraid not the way this patch does it. First of all, it's not a decision for the driver to make, but for the user space, depending on the access pattern it does. It also isn't something specific to vb2-dma-contig only. I remember Sakari had a series that attempted to solve this in a more comprehensive way[1]. I remember it had some minor problems when I reviewed it, but generally the idea seemed sane. Sakari, do you have any plans to revive that work? [1] https://www.mail-archive.com/linux-media@vger.kernel.org/msg112459.html Best regards, Tomasz > > Regards, > > Hans > > > On 10/26/2016 10:52 AM, Thierry Escande wrote: > > From: Heng-Ruey Hsu <henry...@chromium.org> > > > > DMA allocations for MMAP type are uncached by default. But for > > some cases, CPU has to access the buffers. ie: memcpy for format > > converter. Supporting cacheable MMAP improves huge performance. > > > > This patch enables cacheable memory for DMA coherent allocator in mmap > > buffer allocation if non-consistent DMA attribute is set and kernel > > mapping is present. Even if userspace doesn't mmap the buffer, sync > > still should be happening if kernel mapping is present. > > If not done in allocation, it is enabled when memory is mapped from > > userspace (if non-consistent DMA attribute is set). > > > > Signed-off-by: Heng-Ruey Hsu <henry...@chromium.org> > > Tested-by: Heng-ruey Hsu <henry...@chromium.org> > > Reviewed-by: Tomasz Figa <tf...@chromium.org> > > Signed-off-by: Thierry Escande <thierry.esca...@collabora.com> > > --- > > drivers/media/v4l2-core/videobuf2-dma-contig.c | 16 ++++++++++++++++ > > 1 file changed, 16 insertions(+) > > > > diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c > > b/drivers/media/v4l2-core/videobuf2-dma-contig.c > > index 0d9665d..89b534a 100644 > > --- a/drivers/media/v4l2-core/videobuf2-dma-contig.c > > +++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c > > @@ -151,6 +151,10 @@ static void vb2_dc_put(void *buf_priv) > > sg_free_table(buf->sgt_base); > > kfree(buf->sgt_base); > > } > > + if (buf->dma_sgt) { > > + sg_free_table(buf->dma_sgt); > > + kfree(buf->dma_sgt); > > + } > > dma_free_attrs(buf->dev, buf->size, buf->cookie, buf->dma_addr, > > buf->attrs); > > put_device(buf->dev); > > @@ -192,6 +196,14 @@ static void *vb2_dc_alloc(struct device *dev, unsigned > > long attrs, > > buf->handler.put = vb2_dc_put; > > buf->handler.arg = buf; > > > > + /* > > + * Enable cache maintenance. Even if userspace doesn't mmap the > > buffer, > > + * sync still should be happening if kernel mapping is present. > > + */ > > + if (!(buf->attrs & DMA_ATTR_NO_KERNEL_MAPPING) && > > + buf->attrs & DMA_ATTR_NON_CONSISTENT) > > + buf->dma_sgt = vb2_dc_get_base_sgt(buf); > > + > > atomic_inc(&buf->refcount); > > > > return buf; > > @@ -227,6 +239,10 @@ static int vb2_dc_mmap(void *buf_priv, struct > > vm_area_struct *vma) > > > > vma->vm_ops->open(vma); > > > > + /* Enable cache maintenance if not enabled in allocation. */ > > + if (!buf->dma_sgt && buf->attrs & DMA_ATTR_NON_CONSISTENT) > > + buf->dma_sgt = vb2_dc_get_base_sgt(buf); > > + > > pr_debug("%s: mapped dma addr 0x%08lx at 0x%08lx, size %ld\n", > > __func__, (unsigned long)buf->dma_addr, vma->vm_start, > > buf->size); > > >
