git.openwrt.org Git - openwrt/staging/jow.git/blob

   1 From 5631d65a09fe2249d22fad0985c25dc776b41808 Mon Sep 17 00:00:00 2001
   2 From: Naushir Patuck <naush@raspberrypi.com>
   3 Date: Fri, 2 Sep 2022 08:35:35 +0100
   4 Subject: [PATCH] media: bcm2835-unicam: Fix for possible dummy buffer
   5  overrun
   6
   7 The Unicam hardware has been observed to cause a buffer overrun when using the
   8 dummy buffer as a circular buffer. The conditions that cause the overrun are not
   9 fully known, but it seems to occur when the memory bus is heavily loaded.
  10
  11 To avoid the overrun, program the hardware with a buffer size of 0 when using
  12 the dummy buffer. This will cause overrun into the allocated dummy buffer, but
  13 avoid out of bounds writes.
  14
  15 Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
  16 ---
  17  drivers/media/platform/bcm2835/bcm2835-unicam.c | 14 ++++++++------
  18  1 file changed, 8 insertions(+), 6 deletions(-)
  19
  20 --- a/drivers/media/platform/bcm2835/bcm2835-unicam.c
  21 +++ b/drivers/media/platform/bcm2835/bcm2835-unicam.c
  22 @@ -126,8 +126,11 @@ MODULE_PARM_DESC(media_controller, "Use
  23  #define UNICAM_EMBEDDED_SIZE   16384
  24
  25  /*
  26 - * Size of the dummy buffer. Can be any size really, but the DMA
  27 - * allocation works in units of page sizes.
  28 + * Size of the dummy buffer allocation.
  29 + *
  30 + * Due to a HW bug causing buffer overruns in circular buffer mode under certain
  31 + * (not yet fully known) conditions, the dummy buffer allocation is set to a
  32 + * a single page size, but the hardware gets programmed with a buffer size of 0.
  33   */
  34  #define DUMMY_BUF_SIZE         (PAGE_SIZE)
  35
  36 @@ -843,8 +846,7 @@ static void unicam_schedule_dummy_buffer
  37         unicam_dbg(3, dev, "Scheduling dummy buffer for node %d\n",
  38                    node->pad_id);
  39
  40 -       unicam_wr_dma_addr(dev, node->dummy_buf_dma_addr, DUMMY_BUF_SIZE,
  41 -                          node->pad_id);
  42 +       unicam_wr_dma_addr(dev, node->dummy_buf_dma_addr, 0, node->pad_id);
  43         node->next_frm = NULL;
  44  }
  45
  46 @@ -2662,8 +2664,8 @@ static void unicam_stop_streaming(struct
  47                  * This is only really needed if the embedded data pad is
  48                  * disabled before the image pad.
  49                  */
  50 -               unicam_wr_dma_addr(dev, node->dummy_buf_dma_addr,
  51 -                                  DUMMY_BUF_SIZE, METADATA_PAD);
  52 +               unicam_wr_dma_addr(dev, node->dummy_buf_dma_addr, 0,
  53 +                                  METADATA_PAD);
  54         }
  55
  56         /* Clear all queued buffers for the node */