On Sat, 14 Mar 2009, Robert Jarzmik wrote:
> Due to DMA constraints, the DMA chain always transfers bytes
> from the QIF fifos to memory in 8 bytes units. In planar
> formats, that could mean 0 padding between Y and U plane
> (and between U and V plane), which is against YUV422P
> standard.
>
> Therefore, a frame size is required to be a multiple of 16
> (so U plane size is a multiple of 8). It is enforced in
> try_fmt() and set_fmt() primitives, be aligning height then
> width on 4 multiples as need be, to reach a 16 multiple.
>
> Signed-off-by: Robert Jarzmik <robert.jarzmik@xxxxxxx>
> ---
> drivers/media/video/pxa_camera.c | 28 +++++++++++++++++++---------
> 1 files changed, 19 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/media/video/pxa_camera.c b/drivers/media/video/pxa_camera.c
> index e3e6b29..8e5611b 100644
> --- a/drivers/media/video/pxa_camera.c
> +++ b/drivers/media/video/pxa_camera.c
> @@ -162,6 +162,8 @@
> CICR0_PERRM | CICR0_QDM | CICR0_CDM | CICR0_SOFM | \
> CICR0_EOFM | CICR0_FOM)
>
> +#define PIX_YUV422P_ALIGN 16 /* YUV422P pix size should be a multiple of 16 */
What is a "pix size?" Did you mean "picture size?"
> +
> /*
> * Structures
> */
> @@ -241,15 +243,11 @@ static int pxa_videobuf_setup(struct videobuf_queue *vq, unsigned int *count,
>
> dev_dbg(&icd->dev, "count=%d, size=%d\n", *count, *size);
>
> - /* planar capture requires Y, U and V buffers to be page aligned */
> - if (pcdev->channels == 3) {
> - *size = PAGE_ALIGN(icd->width * icd->height); /* Y pages */
> - *size += PAGE_ALIGN(icd->width * icd->height / 2); /* U pages */
> - *size += PAGE_ALIGN(icd->width * icd->height / 2); /* V pages */
> - } else {
> - *size = icd->width * icd->height *
> - ((icd->current_fmt->depth + 7) >> 3);
> - }
> + if (pcdev->channels == 3)
> + *size = icd->width * icd->height * 2;
This is not very obvious, why "* 2". Maybe use
pxa_camera_formats[0].depth / 8 or at least add a comment?
> + else
> + *size = roundup(icd->width * icd->height *
> + ((icd->current_fmt->depth + 7) >> 3), 8);
>
> if (0 == *count)
> *count = 32;
> @@ -1234,6 +1232,18 @@ static int pxa_camera_try_fmt(struct soc_camera_device *icd,
> pix->width = 2048;
> pix->width &= ~0x01;
>
> + /*
> + * YUV422P planar format requires images size to be a 16 bytes
> + * multiple. If not, zeros will be inserted between Y and U planes, and
> + * U and V planes, and YUV422P standard would be violated.
> + */
> + if (xlate->host_fmt->fourcc == V4L2_PIX_FMT_YUV422P) {
> + if (!IS_ALIGNED(pix->width * pix->height, PIX_YUV422P_ALIGN))
> + pix->height = ALIGN(pix->height, PIX_YUV422P_ALIGN / 2);
> + if (!IS_ALIGNED(pix->width * pix->height, PIX_YUV422P_ALIGN))
> + pix->width = ALIGN(pix->width, PIX_YUV422P_ALIGN / 2);
Shouldn't this have been sqrt(PIX_YUV422P_ALIGN) (of course, not
literally) instead of PIX_YUV422P_ALIGN / 2? At least above you say,
height and width shall be 4 bytes aligned, not 8.
> + }
> +
> pix->bytesperline = pix->width *
> DIV_ROUND_UP(xlate->host_fmt->depth, 8);
> pix->sizeimage = pix->height * pix->bytesperline;
> --
> 1.5.6.5
Thanks
Guennadi
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
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