Hi Laurent,
On 11/26/2014 10:00 PM, Laurent Pinchart wrote:
> Hi Hans,
>
> Thank you for the patch.
>
> On Tuesday 18 November 2014 13:51:03 Hans Verkuil wrote:
>> From: Hans Verkuil <hans.verkuil@xxxxxxxxx>
>>
>> Add support for importing dmabuf to videobuf2-dma-sg.
>>
>> Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
>> Acked-by: Pawel Osciak <pawel@xxxxxxxxxx>
>> ---
>> drivers/media/v4l2-core/videobuf2-dma-sg.c | 149 +++++++++++++++++++++++---
>> 1 file changed, 136 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/media/v4l2-core/videobuf2-dma-sg.c
>> b/drivers/media/v4l2-core/videobuf2-dma-sg.c index f671fab..ad6d5c7 100644
>> --- a/drivers/media/v4l2-core/videobuf2-dma-sg.c
>> +++ b/drivers/media/v4l2-core/videobuf2-dma-sg.c
>> @@ -41,11 +41,19 @@ struct vb2_dma_sg_buf {
>> int offset;
>> enum dma_data_direction dma_dir;
>> struct sg_table sg_table;
>> + /*
>> + * This will point to sg_table when used with the MMAP or USERPTR
>> + * memory model, and to the dma_buf sglist when used with the
>> + * DMABUF memory model.
>> + */
>> + struct sg_table *dma_sgt;
>> size_t size;
>> unsigned int num_pages;
>> atomic_t refcount;
>> struct vb2_vmarea_handler handler;
>> struct vm_area_struct *vma;
>> +
>> + struct dma_buf_attachment *db_attach;
>> };
>>
>> static void vb2_dma_sg_put(void *buf_priv);
>> @@ -112,6 +120,7 @@ static void *vb2_dma_sg_alloc(void *alloc_ctx, unsigned
>> long size, buf->size = size;
>> /* size is already page aligned */
>> buf->num_pages = size >> PAGE_SHIFT;
>> + buf->dma_sgt = &buf->sg_table;
>>
>> buf->pages = kzalloc(buf->num_pages * sizeof(struct page *),
>> GFP_KERNEL);
>> @@ -122,7 +131,7 @@ static void *vb2_dma_sg_alloc(void *alloc_ctx, unsigned
>> long size, if (ret)
>> goto fail_pages_alloc;
>>
>> - ret = sg_alloc_table_from_pages(&buf->sg_table, buf->pages,
>> + ret = sg_alloc_table_from_pages(buf->dma_sgt, buf->pages,
>> buf->num_pages, 0, size, GFP_KERNEL);
>> if (ret)
>> goto fail_table_alloc;
>> @@ -171,7 +180,7 @@ static void vb2_dma_sg_put(void *buf_priv)
>> dma_unmap_sg(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
>> if (buf->vaddr)
>> vm_unmap_ram(buf->vaddr, buf->num_pages);
>> - sg_free_table(&buf->sg_table);
>> + sg_free_table(buf->dma_sgt);
>> while (--i >= 0)
>> __free_page(buf->pages[i]);
>> kfree(buf->pages);
>> @@ -183,7 +192,11 @@ static void vb2_dma_sg_put(void *buf_priv)
>> static void vb2_dma_sg_prepare(void *buf_priv)
>> {
>> struct vb2_dma_sg_buf *buf = buf_priv;
>> - struct sg_table *sgt = &buf->sg_table;
>> + struct sg_table *sgt = buf->dma_sgt;
>> +
>> + /* DMABUF exporter will flush the cache for us */
>> + if (buf->db_attach)
>> + return;
>
> Is this actually true ? If you look at the export code in patch 08/12, I don't
> see where the exporter would sync the buffer for the importer device.
I think this was true at some point in the past. It ties in with my comment for
patch 06/12: cpu/device syncing for dma-buf is (and was) broken, although nobody
has noticed since none of the DMABUF-aware drivers that are used as such today
need CPU access to the buffer, or are only used on Intel architectures where
this is all moot. Patches 12-16 of my RFCv6 series really fix this. This particular
comment was copied from the dma-contig version. The basic idea was that when the
driver needs CPU access it will call the vaddr memop, which will map the buffer
for CPU access.
However, I am not sure whether dmabuf actually did the right thing there originally.
Later dmabuf was extended with begin/end_for_cpu_access ops to make this explicit,
but that was never implemented in vb2. That's what the second part of RFCv6 does.
Right now dma-sg is bug-compatible with dma-contig.
I spend 1-2 hours with Pawel in Düsseldorf figuring this out, it is not exactly
trivial to understand.
Regards,
Hans
>
>>
>> dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
>> }
>> @@ -191,7 +204,11 @@ static void vb2_dma_sg_prepare(void *buf_priv)
>> static void vb2_dma_sg_finish(void *buf_priv)
>> {
>> struct vb2_dma_sg_buf *buf = buf_priv;
>> - struct sg_table *sgt = &buf->sg_table;
>> + struct sg_table *sgt = buf->dma_sgt;
>> +
>> + /* DMABUF exporter will flush the cache for us */
>> + if (buf->db_attach)
>> + return;
>>
>> dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
>> }
>> @@ -219,6 +236,7 @@ static void *vb2_dma_sg_get_userptr(void *alloc_ctx,
>> unsigned long vaddr, buf->dma_dir = dma_dir;
>> buf->offset = vaddr & ~PAGE_MASK;
>> buf->size = size;
>> + buf->dma_sgt = &buf->sg_table;
>>
>> first = (vaddr & PAGE_MASK) >> PAGE_SHIFT;
>> last = ((vaddr + size - 1) & PAGE_MASK) >> PAGE_SHIFT;
>> @@ -271,7 +289,7 @@ static void *vb2_dma_sg_get_userptr(void *alloc_ctx,
>> unsigned long vaddr, if (num_pages_from_user != buf->num_pages)
>> goto userptr_fail_get_user_pages;
>>
>> - if (sg_alloc_table_from_pages(&buf->sg_table, buf->pages,
>> + if (sg_alloc_table_from_pages(buf->dma_sgt, buf->pages,
>> buf->num_pages, buf->offset, size, 0))
>> goto userptr_fail_alloc_table_from_pages;
>>
>> @@ -313,7 +331,7 @@ static void vb2_dma_sg_put_userptr(void *buf_priv)
>> dma_unmap_sg(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
>> if (buf->vaddr)
>> vm_unmap_ram(buf->vaddr, buf->num_pages);
>> - sg_free_table(&buf->sg_table);
>> + sg_free_table(buf->dma_sgt);
>> while (--i >= 0) {
>> if (buf->dma_dir == DMA_FROM_DEVICE)
>> set_page_dirty_lock(buf->pages[i]);
>> @@ -331,14 +349,16 @@ static void *vb2_dma_sg_vaddr(void *buf_priv)
>>
>> BUG_ON(!buf);
>>
>> - if (!buf->vaddr)
>> - buf->vaddr = vm_map_ram(buf->pages,
>> - buf->num_pages,
>> - -1,
>> - PAGE_KERNEL);
>> + if (!buf->vaddr) {
>> + if (buf->db_attach)
>> + buf->vaddr = dma_buf_vmap(buf->db_attach->dmabuf);
>> + else
>> + buf->vaddr = vm_map_ram(buf->pages,
>> + buf->num_pages, -1, PAGE_KERNEL);
>> + }
>>
>> /* add offset in case userptr is not page-aligned */
>> - return buf->vaddr + buf->offset;
>> + return buf->vaddr ? buf->vaddr + buf->offset : NULL;
>
> Just nitpicking here, can vm_map_ram fail and return NULL ? If so this change
> is a separate bug fix and should be split to a separate patch.
>
>> }
>>
>> static unsigned int vb2_dma_sg_num_users(void *buf_priv)
>> @@ -385,11 +405,110 @@ static int vb2_dma_sg_mmap(void *buf_priv, struct
>> vm_area_struct *vma) return 0;
>> }
>>
>> +/*********************************************/
>> +/* callbacks for DMABUF buffers */
>> +/*********************************************/
>> +
>> +static int vb2_dma_sg_map_dmabuf(void *mem_priv)
>> +{
>> + struct vb2_dma_sg_buf *buf = mem_priv;
>> + struct sg_table *sgt;
>> +
>> + if (WARN_ON(!buf->db_attach)) {
>> + pr_err("trying to pin a non attached buffer\n");
>> + return -EINVAL;
>> + }
>> +
>> + if (WARN_ON(buf->dma_sgt)) {
>> + pr_err("dmabuf buffer is already pinned\n");
>> + return 0;
>> + }
>> +
>> + /* get the associated scatterlist for this buffer */
>> + sgt = dma_buf_map_attachment(buf->db_attach, buf->dma_dir);
>> + if (IS_ERR(sgt)) {
>> + pr_err("Error getting dmabuf scatterlist\n");
>> + return -EINVAL;
>> + }
>> +
>> + buf->dma_sgt = sgt;
>> + buf->vaddr = NULL;
>> +
>> + return 0;
>> +}
>> +
>> +static void vb2_dma_sg_unmap_dmabuf(void *mem_priv)
>> +{
>> + struct vb2_dma_sg_buf *buf = mem_priv;
>> + struct sg_table *sgt = buf->dma_sgt;
>> +
>> + if (WARN_ON(!buf->db_attach)) {
>> + pr_err("trying to unpin a not attached buffer\n");
>> + return;
>> + }
>> +
>> + if (WARN_ON(!sgt)) {
>> + pr_err("dmabuf buffer is already unpinned\n");
>> + return;
>> + }
>> +
>> + if (buf->vaddr) {
>> + dma_buf_vunmap(buf->db_attach->dmabuf, buf->vaddr);
>> + buf->vaddr = NULL;
>> + }
>> + dma_buf_unmap_attachment(buf->db_attach, sgt, buf->dma_dir);
>> +
>> + buf->dma_sgt = NULL;
>> +}
>> +
>> +static void vb2_dma_sg_detach_dmabuf(void *mem_priv)
>> +{
>> + struct vb2_dma_sg_buf *buf = mem_priv;
>> +
>> + /* if vb2 works correctly you should never detach mapped buffer */
>> + if (WARN_ON(buf->dma_sgt))
>> + vb2_dma_sg_unmap_dmabuf(buf);
>> +
>> + /* detach this attachment */
>> + dma_buf_detach(buf->db_attach->dmabuf, buf->db_attach);
>> + kfree(buf);
>> +}
>> +
>> +static void *vb2_dma_sg_attach_dmabuf(void *alloc_ctx, struct dma_buf
>> *dbuf, + unsigned long size, enum dma_data_direction dma_dir)
>> +{
>> + struct vb2_dma_sg_conf *conf = alloc_ctx;
>> + struct vb2_dma_sg_buf *buf;
>> + struct dma_buf_attachment *dba;
>> +
>> + if (dbuf->size < size)
>> + return ERR_PTR(-EFAULT);
>> +
>> + buf = kzalloc(sizeof(*buf), GFP_KERNEL);
>> + if (!buf)
>> + return ERR_PTR(-ENOMEM);
>> +
>> + buf->dev = conf->dev;
>> + /* create attachment for the dmabuf with the user device */
>> + dba = dma_buf_attach(dbuf, buf->dev);
>> + if (IS_ERR(dba)) {
>> + pr_err("failed to attach dmabuf\n");
>> + kfree(buf);
>> + return dba;
>> + }
>> +
>> + buf->dma_dir = dma_dir;
>> + buf->size = size;
>> + buf->db_attach = dba;
>> +
>> + return buf;
>> +}
>> +
>> static void *vb2_dma_sg_cookie(void *buf_priv)
>> {
>> struct vb2_dma_sg_buf *buf = buf_priv;
>>
>> - return &buf->sg_table;
>> + return buf->dma_sgt;
>> }
>>
>> const struct vb2_mem_ops vb2_dma_sg_memops = {
>> @@ -402,6 +521,10 @@ const struct vb2_mem_ops vb2_dma_sg_memops = {
>> .vaddr = vb2_dma_sg_vaddr,
>> .mmap = vb2_dma_sg_mmap,
>> .num_users = vb2_dma_sg_num_users,
>> + .map_dmabuf = vb2_dma_sg_map_dmabuf,
>> + .unmap_dmabuf = vb2_dma_sg_unmap_dmabuf,
>> + .attach_dmabuf = vb2_dma_sg_attach_dmabuf,
>> + .detach_dmabuf = vb2_dma_sg_detach_dmabuf,
>> .cookie = vb2_dma_sg_cookie,
>> };
>> EXPORT_SYMBOL_GPL(vb2_dma_sg_memops);
>
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