Re: [PATCH v5] [media] vb2: Add support for capture_dma_bidirectional queue flag

[Thierry Escande <thierry.escande@collabora.com>]

Hi Mauro,

On 18/11/2016 19:59, Mauro Carvalho Chehab wrote:
> Em Tue, 25 Oct 2016 10:22:29 +0200
> Thierry Escande <thierry.escande@collabora.com> escreveu:
>
>> From: Pawel Osciak <posciak@chromium.org>
>>
>> When this flag is set for CAPTURE queues by the driver on calling
>> vb2_queue_init(), it forces the buffers on the queue to be
>> allocated/mapped with DMA_BIDIRECTIONAL direction flag instead of
>> DMA_FROM_DEVICE. This allows the device not only to write to the
>> buffers, but also read out from them. This may be useful e.g. for codec
>> hardware which may be using CAPTURE buffers as reference to decode
>> other buffers.
>>
>> This flag is ignored for OUTPUT queues as we don't want to allow HW to
>> be able to write to OUTPUT buffers.
>>
>> This patch introduces 2 macros:
>> VB2_DMA_DIR(q) returns the corresponding dma_dir for the passed queue
>> type, tanking care of the capture_dma_birectional flag.
>>
>> VB2_DMA_DIR_CAPTURE(d) is a test macro returning true if the passed DMA
>> direction refers to a capture buffer. This test is used to map virtual
>> addresses for writing and to mark pages as dirty.
>
> Why to add it? There's no other patch on this series with would
> justify its needs...

It is used by a Rockchip vpu driver which is only in the chromeos public 
tree for now and will be upstreamed soon.

Regards,
  Thierry

>>
>> Signed-off-by: Pawel Osciak <posciak@chromium.org>
>> Tested-by: Pawel Osciak <posciak@chromium.org>
>> Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
>> ---
>>
>> Changes in v2:
>> - Renamed use_dma_bidirectional field as capture_dma_bidirectional
>> - Added a VB2_DMA_DIR() macro
>>
>> Changes in v3:
>> - Get rid of dma_dir field and therefore squashed the previous patch
>>
>> Changes in v4:
>> - Fixed typos in include/media/videobuf2-core.h
>> - Added VB2_DMA_DIR_CAPTURE() test macro
>>
>> Changes in v5:
>> - Use is_output queue field in VB2_DMA_DIR() macro
>>
>>  drivers/media/v4l2-core/videobuf2-core.c       |  9 +++------
>>  drivers/media/v4l2-core/videobuf2-dma-contig.c |  2 +-
>>  drivers/media/v4l2-core/videobuf2-dma-sg.c     |  5 +++--
>>  drivers/media/v4l2-core/videobuf2-vmalloc.c    |  4 ++--
>>  include/media/videobuf2-core.h                 | 23 +++++++++++++++++++++++
>>  5 files changed, 32 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
>> index 21900202..22d6105 100644
>> --- a/drivers/media/v4l2-core/videobuf2-core.c
>> +++ b/drivers/media/v4l2-core/videobuf2-core.c
>> @@ -194,8 +194,7 @@ static void __enqueue_in_driver(struct vb2_buffer *vb);
>>  static int __vb2_buf_mem_alloc(struct vb2_buffer *vb)
>>  {
>>  	struct vb2_queue *q = vb->vb2_queue;
>> -	enum dma_data_direction dma_dir =
>> -		q->is_output ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
>> +	enum dma_data_direction dma_dir = VB2_DMA_DIR(q);
>>  	void *mem_priv;
>>  	int plane;
>>  	int ret = -ENOMEM;
>> @@ -978,8 +977,7 @@ static int __qbuf_userptr(struct vb2_buffer *vb, const void *pb)
>>  	void *mem_priv;
>>  	unsigned int plane;
>>  	int ret = 0;
>> -	enum dma_data_direction dma_dir =
>> -		q->is_output ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
>> +	enum dma_data_direction dma_dir = VB2_DMA_DIR(q);
>>  	bool reacquired = vb->planes[0].mem_priv == NULL;
>>
>>  	memset(planes, 0, sizeof(planes[0]) * vb->num_planes);
>> @@ -1096,8 +1094,7 @@ static int __qbuf_dmabuf(struct vb2_buffer *vb, const void *pb)
>>  	void *mem_priv;
>>  	unsigned int plane;
>>  	int ret = 0;
>> -	enum dma_data_direction dma_dir =
>> -		q->is_output ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
>> +	enum dma_data_direction dma_dir = VB2_DMA_DIR(q);
>>  	bool reacquired = vb->planes[0].mem_priv == NULL;
>>
>>  	memset(planes, 0, sizeof(planes[0]) * vb->num_planes);
>> diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
>> index fb6a177..a44e383 100644
>> --- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
>> +++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
>> @@ -507,7 +507,7 @@ static void *vb2_dc_get_userptr(struct device *dev, unsigned long vaddr,
>>  	buf->dma_dir = dma_dir;
>>
>>  	offset = vaddr & ~PAGE_MASK;
>> -	vec = vb2_create_framevec(vaddr, size, dma_dir == DMA_FROM_DEVICE);
>> +	vec = vb2_create_framevec(vaddr, size, VB2_DMA_DIR_CAPTURE(dma_dir));
>>  	if (IS_ERR(vec)) {
>>  		ret = PTR_ERR(vec);
>>  		goto fail_buf;
>> diff --git a/drivers/media/v4l2-core/videobuf2-dma-sg.c b/drivers/media/v4l2-core/videobuf2-dma-sg.c
>> index ecff8f49..51c98f6 100644
>> --- a/drivers/media/v4l2-core/videobuf2-dma-sg.c
>> +++ b/drivers/media/v4l2-core/videobuf2-dma-sg.c
>> @@ -238,7 +238,8 @@ static void *vb2_dma_sg_get_userptr(struct device *dev, unsigned long vaddr,
>>  	buf->offset = vaddr & ~PAGE_MASK;
>>  	buf->size = size;
>>  	buf->dma_sgt = &buf->sg_table;
>> -	vec = vb2_create_framevec(vaddr, size, buf->dma_dir == DMA_FROM_DEVICE);
>> +	vec = vb2_create_framevec(vaddr, size,
>> +				  VB2_DMA_DIR_CAPTURE(buf->dma_dir));
>>  	if (IS_ERR(vec))
>>  		goto userptr_fail_pfnvec;
>>  	buf->vec = vec;
>> @@ -291,7 +292,7 @@ static void vb2_dma_sg_put_userptr(void *buf_priv)
>>  		vm_unmap_ram(buf->vaddr, buf->num_pages);
>>  	sg_free_table(buf->dma_sgt);
>>  	while (--i >= 0) {
>> -		if (buf->dma_dir == DMA_FROM_DEVICE)
>> +		if (VB2_DMA_DIR_CAPTURE(buf->dma_dir))
>>  			set_page_dirty_lock(buf->pages[i]);
>>  	}
>>  	vb2_destroy_framevec(buf->vec);
>> diff --git a/drivers/media/v4l2-core/videobuf2-vmalloc.c b/drivers/media/v4l2-core/videobuf2-vmalloc.c
>> index ab3227b..76649bd 100644
>> --- a/drivers/media/v4l2-core/videobuf2-vmalloc.c
>> +++ b/drivers/media/v4l2-core/videobuf2-vmalloc.c
>> @@ -86,7 +86,7 @@ static void *vb2_vmalloc_get_userptr(struct device *dev, unsigned long vaddr,
>>  	buf->dma_dir = dma_dir;
>>  	offset = vaddr & ~PAGE_MASK;
>>  	buf->size = size;
>> -	vec = vb2_create_framevec(vaddr, size, dma_dir == DMA_FROM_DEVICE);
>> +	vec = vb2_create_framevec(vaddr, size, VB2_DMA_DIR_CAPTURE(dma_dir));
>>  	if (IS_ERR(vec)) {
>>  		ret = PTR_ERR(vec);
>>  		goto fail_pfnvec_create;
>> @@ -136,7 +136,7 @@ static void vb2_vmalloc_put_userptr(void *buf_priv)
>>  		pages = frame_vector_pages(buf->vec);
>>  		if (vaddr)
>>  			vm_unmap_ram((void *)vaddr, n_pages);
>> -		if (buf->dma_dir == DMA_FROM_DEVICE)
>> +		if (VB2_DMA_DIR_CAPTURE(buf->dma_dir))
>>  			for (i = 0; i < n_pages; i++)
>>  				set_page_dirty_lock(pages[i]);
>>  	} else {
>> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
>> index ac5898a..11d2e51 100644
>> --- a/include/media/videobuf2-core.h
>> +++ b/include/media/videobuf2-core.h
>> @@ -433,6 +433,9 @@ struct vb2_buf_ops {
>>   * @quirk_poll_must_check_waiting_for_buffers: Return POLLERR at poll when QBUF
>>   *              has not been called. This is a vb1 idiom that has been adopted
>>   *              also by vb2.
>> + * @capture_dma_bidirectional:	use DMA_BIDIRECTIONAL for CAPTURE buffers; this
>> + *				allows HW to read from the CAPTURE buffers in
>> + *				addition to writing; ignored for OUTPUT queues.
>>   * @lock:	pointer to a mutex that protects the vb2_queue struct. The
>>   *		driver can set this to a mutex to let the v4l2 core serialize
>>   *		the queuing ioctls. If the driver wants to handle locking
>> @@ -499,6 +502,7 @@ struct vb2_queue {
>>  	unsigned			fileio_write_immediately:1;
>>  	unsigned			allow_zero_bytesused:1;
>>  	unsigned		   quirk_poll_must_check_waiting_for_buffers:1;
>> +	unsigned			capture_dma_bidirectional:1;
>>
>>  	struct mutex			*lock;
>>  	void				*owner;
>> @@ -554,6 +558,25 @@ struct vb2_queue {
>>  #endif
>>  };
>>
>> +/*
>> + * Returns the corresponding DMA direction given the vb2_queue type (capture or
>> + * output). Returns DMA_BIDIRECTIONAL for capture buffers if the vb2_queue field
>> + * capture_dma_bidirectional is set by the driver.
>> + */
>> +#define VB2_DMA_DIR(q) ((q)->is_output ? DMA_TO_DEVICE                  \
>> +				       : (q)->capture_dma_bidirectional \
>> +					 ? DMA_BIDIRECTIONAL            \
>> +					 : DMA_FROM_DEVICE)
>> +
>> +/*
>> + * Returns true if the DMA direction passed as parameter refers to a capture
>> + * buffer as capture buffers allow both FROM_DEVICE and BIDIRECTIONAL DMA
>> + * direction. This test is used to map virtual addresses for writing and to mark
>> + * pages as dirty.
>> + */
>> +#define VB2_DMA_DIR_CAPTURE(d) \
>> +			((d) == DMA_FROM_DEVICE || (d) == DMA_BIDIRECTIONAL)
>> +
>>  /**
>>   * vb2_plane_vaddr() - Return a kernel virtual address of a given plane
>>   * @vb:		vb2_buffer to which the plane in question belongs to
>
>
> Thanks,
> Mauro
>