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Date: Tue, 15 Dec 2020 13:16:48 +0200
From: Stanimir Varbanov <stanimir.varbanov@...aro.org>
To: Alexandre Courbot <acourbot@...omium.org>,
Stanimir Varbanov <stanimir.varbanov@...aro.org>,
Tomasz Figa <tfiga@...omium.org>,
Fritz Koenig <frkoenig@...omium.org>
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arm-msm@...r.kernel.org, Robin Murphy <robin.murphy@....com>
Subject: Re: [PATCH] media: venus: use contig vb2 ops
Hi,
Cc: Robin
On 12/14/20 2:57 PM, Alexandre Courbot wrote:
> This driver uses the SG vb2 ops, but effectively only ever accesses the
> first entry of the SG table, indicating that it expects a flat layout.
> Switch it to use the contiguous ops to make sure this expected invariant
Under what circumstances the sg table will has nents > 1? I came down to
[1] but not sure I got it right.
I'm afraid that for systems with low amount of system memory and when
the memory become fragmented, the driver will not work. That's why I
started with sg allocator.
[1]
https://elixir.bootlin.com/linux/v5.10.1/source/drivers/iommu/dma-iommu.c#L782
> is always enforced. Since the device is supposed to be behind an IOMMU
> this should have little to none practical consequences beyond making the
> driver not rely on a particular behavior of the SG implementation.
>
> Reported-by: Tomasz Figa <tfiga@...omium.org>
> Signed-off-by: Alexandre Courbot <acourbot@...omium.org>
> ---
> Hi everyone,
>
> It probably doesn't hurt to fix this issue before some actual issue happens.
> I have tested this patch on Chrome OS and playback was just as fine as with
> the SG ops.
>
> drivers/media/platform/Kconfig | 2 +-
> drivers/media/platform/qcom/venus/helpers.c | 9 ++-------
> drivers/media/platform/qcom/venus/vdec.c | 6 +++---
> drivers/media/platform/qcom/venus/venc.c | 6 +++---
> 4 files changed, 9 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/media/platform/Kconfig b/drivers/media/platform/Kconfig
> index 35a18d388f3f..d9d7954111f2 100644
> --- a/drivers/media/platform/Kconfig
> +++ b/drivers/media/platform/Kconfig
> @@ -533,7 +533,7 @@ config VIDEO_QCOM_VENUS
> depends on INTERCONNECT || !INTERCONNECT
> select QCOM_MDT_LOADER if ARCH_QCOM
> select QCOM_SCM if ARCH_QCOM
> - select VIDEOBUF2_DMA_SG
> + select VIDEOBUF2_DMA_CONTIG
> select V4L2_MEM2MEM_DEV
> help
> This is a V4L2 driver for Qualcomm Venus video accelerator
> diff --git a/drivers/media/platform/qcom/venus/helpers.c b/drivers/media/platform/qcom/venus/helpers.c
> index 50439eb1ffea..859d260f002b 100644
> --- a/drivers/media/platform/qcom/venus/helpers.c
> +++ b/drivers/media/platform/qcom/venus/helpers.c
> @@ -7,7 +7,7 @@
> #include <linux/mutex.h>
> #include <linux/slab.h>
> #include <linux/kernel.h>
> -#include <media/videobuf2-dma-sg.h>
> +#include <media/videobuf2-dma-contig.h>
> #include <media/v4l2-mem2mem.h>
> #include <asm/div64.h>
>
> @@ -1284,14 +1284,9 @@ int venus_helper_vb2_buf_init(struct vb2_buffer *vb)
> struct venus_inst *inst = vb2_get_drv_priv(vb->vb2_queue);
> struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb);
> struct venus_buffer *buf = to_venus_buffer(vbuf);
> - struct sg_table *sgt;
> -
> - sgt = vb2_dma_sg_plane_desc(vb, 0);
> - if (!sgt)
> - return -EFAULT;
>
> buf->size = vb2_plane_size(vb, 0);
> - buf->dma_addr = sg_dma_address(sgt->sgl);
Can we do it:
if (WARN_ON(sgt->nents > 1))
return -EFAULT;
I understand that logically using dma-sg when the flat layout is
expected by the hardware is wrong, but I haven't seen issues until now.
> + buf->dma_addr = vb2_dma_contig_plane_dma_addr(vb, 0);
>
> if (vb->type == V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE)
> list_add_tail(&buf->reg_list, &inst->registeredbufs);
> diff --git a/drivers/media/platform/qcom/venus/vdec.c b/drivers/media/platform/qcom/venus/vdec.c
> index 8488411204c3..3fb277c81aca 100644
> --- a/drivers/media/platform/qcom/venus/vdec.c
> +++ b/drivers/media/platform/qcom/venus/vdec.c
> @@ -13,7 +13,7 @@
> #include <media/v4l2-event.h>
> #include <media/v4l2-ctrls.h>
> #include <media/v4l2-mem2mem.h>
> -#include <media/videobuf2-dma-sg.h>
> +#include <media/videobuf2-dma-contig.h>
>
> #include "hfi_venus_io.h"
> #include "hfi_parser.h"
> @@ -1461,7 +1461,7 @@ static int m2m_queue_init(void *priv, struct vb2_queue *src_vq,
> src_vq->io_modes = VB2_MMAP | VB2_DMABUF;
> src_vq->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_COPY;
> src_vq->ops = &vdec_vb2_ops;
> - src_vq->mem_ops = &vb2_dma_sg_memops;
> + src_vq->mem_ops = &vb2_dma_contig_memops;
> src_vq->drv_priv = inst;
> src_vq->buf_struct_size = sizeof(struct venus_buffer);
> src_vq->allow_zero_bytesused = 1;
> @@ -1475,7 +1475,7 @@ static int m2m_queue_init(void *priv, struct vb2_queue *src_vq,
> dst_vq->io_modes = VB2_MMAP | VB2_DMABUF;
> dst_vq->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_COPY;
> dst_vq->ops = &vdec_vb2_ops;
> - dst_vq->mem_ops = &vb2_dma_sg_memops;
> + dst_vq->mem_ops = &vb2_dma_contig_memops;
> dst_vq->drv_priv = inst;
> dst_vq->buf_struct_size = sizeof(struct venus_buffer);
> dst_vq->allow_zero_bytesused = 1;
> diff --git a/drivers/media/platform/qcom/venus/venc.c b/drivers/media/platform/qcom/venus/venc.c
> index 1c61602c5de1..a09550cd1dba 100644
> --- a/drivers/media/platform/qcom/venus/venc.c
> +++ b/drivers/media/platform/qcom/venus/venc.c
> @@ -10,7 +10,7 @@
> #include <linux/pm_runtime.h>
> #include <linux/slab.h>
> #include <media/v4l2-mem2mem.h>
> -#include <media/videobuf2-dma-sg.h>
> +#include <media/videobuf2-dma-contig.h>
> #include <media/v4l2-ioctl.h>
> #include <media/v4l2-event.h>
> #include <media/v4l2-ctrls.h>
> @@ -1001,7 +1001,7 @@ static int m2m_queue_init(void *priv, struct vb2_queue *src_vq,
> src_vq->io_modes = VB2_MMAP | VB2_USERPTR | VB2_DMABUF;
> src_vq->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_COPY;
> src_vq->ops = &venc_vb2_ops;
> - src_vq->mem_ops = &vb2_dma_sg_memops;
> + src_vq->mem_ops = &vb2_dma_contig_memops;
> src_vq->drv_priv = inst;
> src_vq->buf_struct_size = sizeof(struct venus_buffer);
> src_vq->allow_zero_bytesused = 1;
> @@ -1017,7 +1017,7 @@ static int m2m_queue_init(void *priv, struct vb2_queue *src_vq,
> dst_vq->io_modes = VB2_MMAP | VB2_USERPTR | VB2_DMABUF;
> dst_vq->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_COPY;
> dst_vq->ops = &venc_vb2_ops;
> - dst_vq->mem_ops = &vb2_dma_sg_memops;
> + dst_vq->mem_ops = &vb2_dma_contig_memops;
> dst_vq->drv_priv = inst;
> dst_vq->buf_struct_size = sizeof(struct venus_buffer);
> dst_vq->allow_zero_bytesused = 1;
>
--
regards,
Stan
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