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-rw-r--r--Documentation/video4linux/cx2341x/fw-dma.txt16
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