bcm2835-unicam: Increase the size of the dummy buffer

Increase the size of the dummy buffer to store a single line of 64 Mpix
resolution at 10bpp.

This is a speculative change to avoid possible hardware overruns when running
in a circular buffer modes. It is unclear if the hardware checks for overruns
on every AXI write, or on line boundaries.

Signed-off-by: Naushir Patuck <[email protected]>

Author: naushir

drivers/media/platform/bcm2835/bcm2835-unicam.c

@@ -127,15 +127,15 @@ MODULE_PARM_DESC(media_controller, "Use media controller API");
 #define UNICAM_EMBEDDED_SIZE	16384
 
 /*
- * Size of the dummy buffer. Can be any size really, but the DMA
- * allocation works in units of page sizes.
+ * Size of the dummy buffer. This is currently sized to fill a single line of
+ * 64 Mpix resolution at 10bpp.
  *
  * Due to a HW bug causing buffer overruns in circular buffer mode under certain
  * (not yet fully known) conditions, the dummy buffer allocation is twice as big
  * as needed, and the buffer end address register is calculated with a size of
  * DUMMY_BUF_SIZE.
  */
-#define DUMMY_BUF_SIZE		(PAGE_SIZE)
+#define DUMMY_BUF_SIZE		(PAGE_SIZE * 6)
 #define DUMMY_BUF_ALLOC_SIZE	(DUMMY_BUF_SIZE * 2)
 
 enum pad_types {