Re: [PATCH] media: cedrus: Don't kernel map most buffers

From: Hans Verkuil
Date: Mon Oct 04 2021 - 04:11:24 EST

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Next in thread: Jernej Škrabec: "Re: Re: [PATCH] media: cedrus: Don't kernel map most buffers"
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Hi Jernej,

Some comments below:

On 12/09/2021 08:08, Jernej Skrabec wrote:
> Except VP8 probability coefficients buffer, all other buffers are never

Except -> Except for

> accessed by CPU. That allows us to mark them with DMA_ATTR_NO_KERNEL_MAPPING
> flag. This helps with decoding big (like 4k) videos on 32-bit ARM
> platforms where default vmalloc size is relatively small - 240 MiB.
> Since auxiliary buffer are not yet efficiently allocated, this can be
> easily exceeded. Even if allocation is optimized, 4k videos will still
> often exceed this limit.
>
> Signed-off-by: Jernej Skrabec <jernej.skrabec@xxxxxxxxx>
> ---
> .../staging/media/sunxi/cedrus/cedrus_h264.c | 102 ++++++++++--------
> .../staging/media/sunxi/cedrus/cedrus_h265.c | 28 ++---
> .../staging/media/sunxi/cedrus/cedrus_video.c | 2 +
> 3 files changed, 73 insertions(+), 59 deletions(-)
>
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_h264.c b/drivers/staging/media/sunxi/cedrus/cedrus_h264.c
> index de7442d4834d..6e38b37d9fe1 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus_h264.c
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_h264.c
> @@ -538,23 +538,23 @@ static int cedrus_h264_start(struct cedrus_ctx *ctx)
>
> ctx->codec.h264.pic_info_buf_size = pic_info_size;
> ctx->codec.h264.pic_info_buf =
> - dma_alloc_coherent(dev->dev, ctx->codec.h264.pic_info_buf_size,
> - &ctx->codec.h264.pic_info_buf_dma,
> - GFP_KERNEL);
> + dma_alloc_attrs(dev->dev, ctx->codec.h264.pic_info_buf_size,
> + &ctx->codec.h264.pic_info_buf_dma,
> + GFP_KERNEL, DMA_ATTR_NO_KERNEL_MAPPING);
> if (!ctx->codec.h264.pic_info_buf)
> return -ENOMEM;
>
> /*
> * That buffer is supposed to be 16kiB in size, and be aligned
> - * on 16kiB as well. However, dma_alloc_coherent provides the
> + * on 16kiB as well. However, dma_alloc_attrs provides the
> * guarantee that we'll have a CPU and DMA address aligned on

Does the 'CPU' part of this sentence still make sense since the CPU
won't access the buffer?

> * the smallest page order that is greater to the requested
> * size, so we don't have to overallocate.
> */
> ctx->codec.h264.neighbor_info_buf =
> - dma_alloc_coherent(dev->dev, CEDRUS_NEIGHBOR_INFO_BUF_SIZE,
> - &ctx->codec.h264.neighbor_info_buf_dma,
> - GFP_KERNEL);
> + dma_alloc_attrs(dev->dev, CEDRUS_NEIGHBOR_INFO_BUF_SIZE,
> + &ctx->codec.h264.neighbor_info_buf_dma,
> + GFP_KERNEL, DMA_ATTR_NO_KERNEL_MAPPING);

I think it would be good to have a comment for all these dma_alloc_attrs
calls where you note that these buffers are used by the HW only, and
never by the CPU, hence the use of DMA_ATTR_NO_KERNEL_MAPPING.

> if (!ctx->codec.h264.neighbor_info_buf) {
> ret = -ENOMEM;
> goto err_pic_buf;
> @@ -582,10 +582,11 @@ static int cedrus_h264_start(struct cedrus_ctx *ctx)
>
> mv_col_size = field_size * 2 * CEDRUS_H264_FRAME_NUM;
> ctx->codec.h264.mv_col_buf_size = mv_col_size;
> - ctx->codec.h264.mv_col_buf = dma_alloc_coherent(dev->dev,
> - ctx->codec.h264.mv_col_buf_size,
> - &ctx->codec.h264.mv_col_buf_dma,
> - GFP_KERNEL);
> + ctx->codec.h264.mv_col_buf =
> + dma_alloc_attrs(dev->dev,
> + ctx->codec.h264.mv_col_buf_size,
> + &ctx->codec.h264.mv_col_buf_dma,
> + GFP_KERNEL, DMA_ATTR_NO_KERNEL_MAPPING);
> if (!ctx->codec.h264.mv_col_buf) {
> ret = -ENOMEM;
> goto err_neighbor_buf;
> @@ -600,10 +601,10 @@ static int cedrus_h264_start(struct cedrus_ctx *ctx)
> ctx->codec.h264.deblk_buf_size =
> ALIGN(ctx->src_fmt.width, 32) * 12;
> ctx->codec.h264.deblk_buf =
> - dma_alloc_coherent(dev->dev,
> - ctx->codec.h264.deblk_buf_size,
> - &ctx->codec.h264.deblk_buf_dma,
> - GFP_KERNEL);
> + dma_alloc_attrs(dev->dev,
> + ctx->codec.h264.deblk_buf_size,
> + &ctx->codec.h264.deblk_buf_dma,
> + GFP_KERNEL, DMA_ATTR_NO_KERNEL_MAPPING);
> if (!ctx->codec.h264.deblk_buf) {
> ret = -ENOMEM;
> goto err_mv_col_buf;
> @@ -616,10 +617,10 @@ static int cedrus_h264_start(struct cedrus_ctx *ctx)
> ctx->codec.h264.intra_pred_buf_size =
> ALIGN(ctx->src_fmt.width, 64) * 5 * 2;
> ctx->codec.h264.intra_pred_buf =
> - dma_alloc_coherent(dev->dev,
> - ctx->codec.h264.intra_pred_buf_size,
> - &ctx->codec.h264.intra_pred_buf_dma,
> - GFP_KERNEL);
> + dma_alloc_attrs(dev->dev,
> + ctx->codec.h264.intra_pred_buf_size,
> + &ctx->codec.h264.intra_pred_buf_dma,
> + GFP_KERNEL, DMA_ATTR_NO_KERNEL_MAPPING);
> if (!ctx->codec.h264.intra_pred_buf) {
> ret = -ENOMEM;
> goto err_deblk_buf;
> @@ -629,24 +630,28 @@ static int cedrus_h264_start(struct cedrus_ctx *ctx)
> return 0;
>
> err_deblk_buf:
> - dma_free_coherent(dev->dev, ctx->codec.h264.deblk_buf_size,
> - ctx->codec.h264.deblk_buf,
> - ctx->codec.h264.deblk_buf_dma);
> + dma_free_attrs(dev->dev, ctx->codec.h264.deblk_buf_size,
> + ctx->codec.h264.deblk_buf,
> + ctx->codec.h264.deblk_buf_dma,
> + DMA_ATTR_NO_KERNEL_MAPPING);
>
> err_mv_col_buf:
> - dma_free_coherent(dev->dev, ctx->codec.h264.mv_col_buf_size,
> - ctx->codec.h264.mv_col_buf,
> - ctx->codec.h264.mv_col_buf_dma);
> + dma_free_attrs(dev->dev, ctx->codec.h264.mv_col_buf_size,
> + ctx->codec.h264.mv_col_buf,
> + ctx->codec.h264.mv_col_buf_dma,
> + DMA_ATTR_NO_KERNEL_MAPPING);
>
> err_neighbor_buf:
> - dma_free_coherent(dev->dev, CEDRUS_NEIGHBOR_INFO_BUF_SIZE,
> - ctx->codec.h264.neighbor_info_buf,
> - ctx->codec.h264.neighbor_info_buf_dma);
> + dma_free_attrs(dev->dev, CEDRUS_NEIGHBOR_INFO_BUF_SIZE,
> + ctx->codec.h264.neighbor_info_buf,
> + ctx->codec.h264.neighbor_info_buf_dma,
> + DMA_ATTR_NO_KERNEL_MAPPING);
>
> err_pic_buf:
> - dma_free_coherent(dev->dev, ctx->codec.h264.pic_info_buf_size,
> - ctx->codec.h264.pic_info_buf,
> - ctx->codec.h264.pic_info_buf_dma);
> + dma_free_attrs(dev->dev, ctx->codec.h264.pic_info_buf_size,
> + ctx->codec.h264.pic_info_buf,
> + ctx->codec.h264.pic_info_buf_dma,
> + DMA_ATTR_NO_KERNEL_MAPPING);
> return ret;
> }
>
> @@ -654,23 +659,28 @@ static void cedrus_h264_stop(struct cedrus_ctx *ctx)
> {
> struct cedrus_dev *dev = ctx->dev;
>
> - dma_free_coherent(dev->dev, ctx->codec.h264.mv_col_buf_size,
> - ctx->codec.h264.mv_col_buf,
> - ctx->codec.h264.mv_col_buf_dma);
> - dma_free_coherent(dev->dev, CEDRUS_NEIGHBOR_INFO_BUF_SIZE,
> - ctx->codec.h264.neighbor_info_buf,
> - ctx->codec.h264.neighbor_info_buf_dma);
> - dma_free_coherent(dev->dev, ctx->codec.h264.pic_info_buf_size,
> - ctx->codec.h264.pic_info_buf,
> - ctx->codec.h264.pic_info_buf_dma);
> + dma_free_attrs(dev->dev, ctx->codec.h264.mv_col_buf_size,
> + ctx->codec.h264.mv_col_buf,
> + ctx->codec.h264.mv_col_buf_dma,
> + DMA_ATTR_NO_KERNEL_MAPPING);
> + dma_free_attrs(dev->dev, CEDRUS_NEIGHBOR_INFO_BUF_SIZE,
> + ctx->codec.h264.neighbor_info_buf,
> + ctx->codec.h264.neighbor_info_buf_dma,
> + DMA_ATTR_NO_KERNEL_MAPPING);
> + dma_free_attrs(dev->dev, ctx->codec.h264.pic_info_buf_size,
> + ctx->codec.h264.pic_info_buf,
> + ctx->codec.h264.pic_info_buf_dma,
> + DMA_ATTR_NO_KERNEL_MAPPING);
> if (ctx->codec.h264.deblk_buf_size)
> - dma_free_coherent(dev->dev, ctx->codec.h264.deblk_buf_size,
> - ctx->codec.h264.deblk_buf,
> - ctx->codec.h264.deblk_buf_dma);
> + dma_free_attrs(dev->dev, ctx->codec.h264.deblk_buf_size,
> + ctx->codec.h264.deblk_buf,
> + ctx->codec.h264.deblk_buf_dma,
> + DMA_ATTR_NO_KERNEL_MAPPING);
> if (ctx->codec.h264.intra_pred_buf_size)
> - dma_free_coherent(dev->dev, ctx->codec.h264.intra_pred_buf_size,
> - ctx->codec.h264.intra_pred_buf,
> - ctx->codec.h264.intra_pred_buf_dma);
> + dma_free_attrs(dev->dev, ctx->codec.h264.intra_pred_buf_size,
> + ctx->codec.h264.intra_pred_buf,
> + ctx->codec.h264.intra_pred_buf_dma,
> + DMA_ATTR_NO_KERNEL_MAPPING);
> }
>
> static void cedrus_h264_trigger(struct cedrus_ctx *ctx)
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> index 3d9561d4aadb..bb7eb56106c5 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> @@ -351,10 +351,10 @@ static void cedrus_h265_setup(struct cedrus_ctx *ctx,
> ctx->codec.h265.mv_col_buf_unit_size;
>
> ctx->codec.h265.mv_col_buf =
> - dma_alloc_coherent(dev->dev,
> - ctx->codec.h265.mv_col_buf_size,
> - &ctx->codec.h265.mv_col_buf_addr,
> - GFP_KERNEL);
> + dma_alloc_attrs(dev->dev,
> + ctx->codec.h265.mv_col_buf_size,
> + &ctx->codec.h265.mv_col_buf_addr,
> + GFP_KERNEL, DMA_ATTR_NO_KERNEL_MAPPING);
> if (!ctx->codec.h265.mv_col_buf) {
> ctx->codec.h265.mv_col_buf_size = 0;
> // TODO: Abort the process here.
> @@ -668,9 +668,9 @@ static int cedrus_h265_start(struct cedrus_ctx *ctx)
> ctx->codec.h265.mv_col_buf_size = 0;
>
> ctx->codec.h265.neighbor_info_buf =
> - dma_alloc_coherent(dev->dev, CEDRUS_H265_NEIGHBOR_INFO_BUF_SIZE,
> - &ctx->codec.h265.neighbor_info_buf_addr,
> - GFP_KERNEL);
> + dma_alloc_attrs(dev->dev, CEDRUS_H265_NEIGHBOR_INFO_BUF_SIZE,
> + &ctx->codec.h265.neighbor_info_buf_addr,
> + GFP_KERNEL, DMA_ATTR_NO_KERNEL_MAPPING);
> if (!ctx->codec.h265.neighbor_info_buf)
> return -ENOMEM;
>
> @@ -682,16 +682,18 @@ static void cedrus_h265_stop(struct cedrus_ctx *ctx)
> struct cedrus_dev *dev = ctx->dev;
>
> if (ctx->codec.h265.mv_col_buf_size > 0) {
> - dma_free_coherent(dev->dev, ctx->codec.h265.mv_col_buf_size,
> - ctx->codec.h265.mv_col_buf,
> - ctx->codec.h265.mv_col_buf_addr);
> + dma_free_attrs(dev->dev, ctx->codec.h265.mv_col_buf_size,
> + ctx->codec.h265.mv_col_buf,
> + ctx->codec.h265.mv_col_buf_addr,
> + DMA_ATTR_NO_KERNEL_MAPPING);
>
> ctx->codec.h265.mv_col_buf_size = 0;
> }
>
> - dma_free_coherent(dev->dev, CEDRUS_H265_NEIGHBOR_INFO_BUF_SIZE,
> - ctx->codec.h265.neighbor_info_buf,
> - ctx->codec.h265.neighbor_info_buf_addr);
> + dma_free_attrs(dev->dev, CEDRUS_H265_NEIGHBOR_INFO_BUF_SIZE,
> + ctx->codec.h265.neighbor_info_buf,
> + ctx->codec.h265.neighbor_info_buf_addr,
> + DMA_ATTR_NO_KERNEL_MAPPING);
> }
>
> static void cedrus_h265_trigger(struct cedrus_ctx *ctx)
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_video.c b/drivers/staging/media/sunxi/cedrus/cedrus_video.c
> index 66714609b577..800ffa5382de 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus_video.c
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_video.c
> @@ -568,6 +568,7 @@ int cedrus_queue_init(void *priv, struct vb2_queue *src_vq,
>
> src_vq->type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
> src_vq->io_modes = VB2_MMAP | VB2_DMABUF;
> + src_vq->dma_attrs = DMA_ATTR_NO_KERNEL_MAPPING;
> src_vq->drv_priv = ctx;
> src_vq->buf_struct_size = sizeof(struct cedrus_buffer);
> src_vq->ops = &cedrus_qops;
> @@ -584,6 +585,7 @@ int cedrus_queue_init(void *priv, struct vb2_queue *src_vq,
>
> dst_vq->type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
> dst_vq->io_modes = VB2_MMAP | VB2_DMABUF;
> + src_vq->dma_attrs = DMA_ATTR_NO_KERNEL_MAPPING;

This should be dst_vq!

I'm also not quite sure that it is right to use this for the destination
buffer. Could this cause problems if this buffer is exported to a dmabuf
and another driver will be using it and requiring a kernel mapping.

Regards,

Hans

> dst_vq->drv_priv = ctx;
> dst_vq->buf_struct_size = sizeof(struct cedrus_buffer);
> dst_vq->ops = &cedrus_qops;
>

Next message: Shawn Guo: "Re: [PATCH v2 0/8] arm64: dts: initial NXP S32G2 support"
Previous message: Dan Carpenter: "[chenxing:msc313_mainlining 55/62] drivers/gpio/gpiolib.c:1130 gpiochip_hierarchy_irq_domain_alloc() warn: variable dereferenced before check 'd->parent' (see line 1119)"
Next in thread: Jernej Škrabec: "Re: Re: [PATCH] media: cedrus: Don't kernel map most buffers"
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