diff options
Diffstat (limited to 'Documentation/video4linux/cx2341x/fw-dma.txt')
| -rw-r--r-- | Documentation/video4linux/cx2341x/fw-dma.txt | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/Documentation/video4linux/cx2341x/fw-dma.txt b/Documentation/video4linux/cx2341x/fw-dma.txt index 8123e262d5b6..be52b6fd1e9a 100644 --- a/Documentation/video4linux/cx2341x/fw-dma.txt +++ b/Documentation/video4linux/cx2341x/fw-dma.txt @@ -22,6 +22,8 @@ urged to choose a smaller block size and learn the scatter-gather technique. Mailbox #10 is reserved for DMA transfer information. +Note: the hardware expects little-endian data ('intel format'). + Flow ==== @@ -64,7 +66,7 @@ addresses are the physical memory location of the target DMA buffer. Each S-G array element is a struct of three 32-bit words. The first word is the source address, the second is the destination address. Both take up the -entire 32 bits. The lowest 16 bits of the third word is the transfer byte +entire 32 bits. The lowest 18 bits of the third word is the transfer byte count. The high-bit of the third word is the "last" flag. The last-flag tells the card to raise the DMA_DONE interrupt. From hard personal experience, if you forget to set this bit, the card will still "work" but the stream will @@ -78,8 +80,8 @@ Array Element: - 32-bit Source Address - 32-bit Destination Address -- 16-bit reserved (high bit is the last flag) -- 16-bit byte count +- 14-bit reserved (high bit is the last flag) +- 18-bit byte count DMA Transfer Status =================== @@ -87,8 +89,8 @@ DMA Transfer Status Register 0x0004 holds the DMA Transfer Status: Bit -4 Scatter-Gather array error -3 DMA write error -2 DMA read error -1 write completed 0 read completed +1 write completed +2 DMA read error +3 DMA write error +4 Scatter-Gather array error |