lkml.org 
[lkml]   [2020]   [Dec]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [PATCH] media: venus: use contig vb2 ops
    From
    Date
    On 2020-12-15 11:16, Stanimir Varbanov wrote:
    > 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.

    Despite what videobuf-dma-contig seems to assume, dma_alloc_coherent()
    makes no guarantee of providing physically contiguous memory. What it
    provides is *DMA contiguous* memory, i.e. from the point of view of the
    device. When an IOMMU is present and managed by the DMA API, such
    buffers may be assembled out of physically-scattered pages (particularly
    under memory pressure/fragmentation).

    Robin.

    >
    > [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@chromium.org>
    >> Signed-off-by: Alexandre Courbot <acourbot@chromium.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;
    >>
    >

    \
     
     \ /
      Last update: 2020-12-15 12:38    [W:5.220 / U:3.324 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site