When bouncing pages, allow a new option to preserve the intra-page

offset.  This is needed for the ehci hardware buffer rings that assume
this behavior.

This is an interim solution, and a more general one is being worked
on.  This solution doesn't break anything that doesn't ask for it
directly.  The mbuf and uio variants with this flag likely don't work
and haven't been tested.

Universe builds with these changes.  I don't have a huge-memory
machine to test these changes with, but will be happy to work with
folks that do and hps if this changes turns out not to be sufficient.

Submitted by:	alfred@ from Hans Peter Selasky's original

1 files changed, 7 insertions, 0 deletions

diff --git a/sys/sys/bus_dma.h b/sys/sys/bus_dma.h
index f89d522..0dad326 100644
--- a/sys/sys/bus_dma.h
+++ b/sys/sys/bus_dma.h
@@ -102,6 +102,13 @@
 #define	BUS_DMA_NOWRITE		0x100
 #define	BUS_DMA_NOCACHE		0x200
 
+/*
+ * The following flag is a DMA tag hint that the page offset of the
+ * loaded kernel virtual address must be preserved in the first
+ * physical segment address, when the KVA is loaded into DMA.
+ */
+#define	BUS_DMA_KEEP_PG_OFFSET	0x400
+
 /* Forwards needed by prototypes below. */
 struct mbuf;
 struct uio;