- Document the new bus_dmamap_sync() interface and related changes.

- Add an AUTHOR section, and fill it in with the folks involved with
  designing and implementing this interface.

share/man/man9/bus_dma.9

@@ -1,6 +1,6 @@
-.\" $NetBSD: bus_dma.9,v 1.7 1997/11/11 10:06:50 mrg Exp $
+.\"	$NetBSD: bus_dma.9,v 1.8 1998/02/04 06:42:53 thorpej Exp $
 .\"
-.\" Copyright (c) 1996, 1997 The NetBSD Foundation, Inc.
+.\" Copyright (c) 1996, 1997, 1998 The NetBSD Foundation, Inc.
 .\" All rights reserved.
 .\" 
 .\" This code is derived from software contributed to The NetBSD Foundation
@@ -35,7 +35,7 @@
 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 .\" POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd Aug 11, 1997
+.Dd February 3, 1998
 .Dt BUS_DMA 9
 .Os NetBSD
 .Sh NAME
@@ -77,7 +77,7 @@
 .Fn bus_dmamap_unload "bus_dma_tag_t tag" "bus_dmamap_t dmam"
 .Ft void
 .Fn bus_dmamap_sync "bus_dma_tag_t tag" "bus_dmamap_t dmam" \
-"bus_dmasync_op_t op"
+"bus_addr_t offset" "bus_size_t len" "int ops"
 .Ft int
 .Fn bus_dmamem_alloc "bus_dma_tag_t tag" "bus_size_t size" \
 "bus_size_t alignment" "bus_size_t boundary" "bus_dma_segment_t *segs" \
@@ -132,31 +132,23 @@ DMA controller address and length registers.
 .It Fa bus_dmamap_t
 A pointer to a structure with at least the following members:
 .Bd -literal
+	bus_size_t	dm_mapsize;
+	int		dm_nsegs;
 	bus_dma_segment_t *dm_segs;
-	int	dm_nsegs;
 .Ed
 .sp
 The structure may have machine-dependent members and arbitrary layout.
 The
+.Fa dm_mapsize
+member indicates the size of the mapping.  A value of 0 indicates the
+mapping is invalid.
+The
 .Fa dm_segs
 member may be an array of segments or a pointer to an
 array of segments.  The
 .Fa dm_nsegs
 member indicates the number of segments in
 .Fa dm_segs .
-A value of 0 indicates the mapping is invalid.
-.It Fa bus_dmasync_op_t
-An enumerated type providing the following unique values:
-.Bd -literal
-	BUS_DMASYNC_PREREAD
-	BUS_DMASYNC_POSTREAD
-	BUS_DMASYNC_PREWRITE
-	BUS_DMASYNC_POSTWRITE
-.Ed
-.sp
-See 
-.Fn bus_dmamap_sync
-for more details.
 .El
 .Sh FUNCTIONS
 .Bl -tag -width compact
@@ -348,18 +340,24 @@ Behavior is not defined if invalid arguments are passed to
 If given valid arguments,
 .Fn bus_dmamap_unload
 always succeeds.
-.It Fn bus_dmamap_sync "tag" "dmam" "op"
+.It Fn bus_dmamap_sync "tag" "dmam" "offset" "len" "ops"
 Performs pre- and post-DMA operation cache and/or buffer synchronization.
 Arguments are as follows:
-.Bl -tag -width dmam -compact
+.Bl -tag -width offset -compact
 .It Fa tag
 This is the bus_dma_tag_t passed down from the parent driver via
 .Fa <bus>_attach_args .
 .It Fa dmam
 The DMA mapping to be synchronized.
-.It Fa op
-The synchronization operation to perform.  The following DMA synchronization
-operations are defined:
+.It Fa offset
+The offset into the DMA mapping to synchronize.
+.It Fa len
+The length of the mapping from
+.Fa offset
+to synchronize.
+.It Fa ops
+One or more synchronization operation to perform.  The following DMA
+synchronization operations are defined:
 .Bl -tag -width BUS_DMASYNC_POSTWRITE -compact
 .It Dv BUS_DMASYNC_PREREAD
 Perform any pre-read DMA cache and/or bounce operations.
@@ -370,8 +368,38 @@ Perform any pre-write DMA cache and/or bounce operations.
 .It Dv BUS_DMASYNC_POSTWRITE
 Perform any post-write DMA cache and/or bounce operations.
 .El
+.Pp
+More than one operation may performed in a given synchronization call.
+Mixing of
+.Em PRE
+and
+.Em POST
+operations is not allowed, and behavior is undefined if this is attempted.
 .El
 .Pp
+Synchronization operations are expressed from the perspective of
+the host RAM, e.g. a
+.Em "device -> memory"
+operation is a
+.Em READ
+and a
+.Em "memory -> device"
+operation is a
+.Em WRITE .
+.Pp
+.Fn bus_dmamp_sync
+may consult state kept within the DMA map to determine if the memory
+is mapped in a DMA coherent fashion.  If so,
+.Fn bus_dmamap_sync
+may elect to skip certain expensive operations, such as flushing
+of the data cache.  See
+.Fn bus_dmamem_map
+for more information on this subject.
+.Pp
+On platforms which implement reordered stores,
+.Fn bus_dmamap_sync
+will always cause the store buffer to be flushed.
+.Pp
 This function exists so that multiple read and write transfers can be
 performed with the same buffer, and so that drivers can explicitly
 inform the
@@ -521,7 +549,7 @@ The size of the mapping.
 Filled in to specify the kernel virtual address where the memory is mapped.
 .It Fa flags
 Flags are defined as follows:
-.Bl -tag -width BUS_DMAMEM_NOSYNC -compact
+.Bl -tag -width BUS_DMA_COHERENT -compact
 .It Dv BUS_DMA_WAITOK
 It is safe to wait (sleep) for resources during this call.
 .It Dv BUS_DMA_NOWAIT
@@ -529,14 +557,23 @@ It is not safe to wait (sleep) for resources during this call.
 .It Dv BUS_DMA_BUS[1-4]
 These flags are placeholders, and may be used by busses to provide
 bus-dependent functionality.
-.It Dv BUS_DMAMEM_NOSYNC
-Map the memory in such a way that synchronization of the map with
-.Fn bus_dmamap_sync
-will not be required.  This is especially useful in
-the case of descriptor blocks which are occasionally read/written by
-the device and host as a means of command/status communications, for
-which map synchronization would be unnecessarily expensive.  This flag
-should be used with care.
+.It Dv BUS_DMA_COHERENT
+This flag is a
+.Em hint
+to machine-dependent code.  If possible, map the memory in such a way
+as it will be DMA coherent.  This may include mapping the pages into
+uncached address space or setting the cache-inhibit bits in page table
+entries.  If implementation of DMA coherent mappings is impossible, this
+is ignored.
+.Pp
+Later, when this memory is loaded into a DMA map, machine-dependent code
+will take whatever steps are necessary to determine if the memory was
+mapped in a DMA coherent fashion.  This may include checking if the
+kernel virtual address lies within uncached address space or if the
+cache-inhibit bits are set in page table entries.  If it is determined
+that the mapping is DMA coherent, state may be placed into the DMA map
+for use by later calls to
+.Fn bus_dmamap_sync .
 .El
 .El
 .Pp
@@ -592,7 +629,7 @@ The offset of the page in DMA memory which is to be mapped.
 The protection codes for the mapping.
 .It Fa flags
 Flags are defined as follows:
-.Bl -tag -width BUS_DMAMEM_NOSYNC -compact
+.Bl -tag -width BUS_DMA_COHERENT -compact
 .It Dv BUS_DMA_WAITOK
 It is safe to wait (sleep) for resources during this call.
 .It Dv BUS_DMA_NOWAIT
@@ -600,14 +637,10 @@ It is not safe to wait (sleep) for resources during this call.
 .It Dv BUS_DMA_BUS[1-4]
 These flags are placeholders, and may be used by busses to provide
 bus-dependent functionality.
-.It Dv BUS_DMAMEM_NOSYNC
-Map the memory in such a way that synchronization of the map with
-.Fn bus_dmamap_sync
-will not
-be required.  This is especially useful in the case of descriptor
-blocks which are occasionally read/written by the device and host as a
-means of command/status communications, for which map synchronization
-would be unnecessarily expensive.  This flag should be used with care.
+.It Dv BUS_DMA_COHERENT
+See
+.Fn bus_dmamem_map
+above for a description of this flag.
 .El
 .El
 .Pp
@@ -619,8 +652,17 @@ Returns -1 to indicate failure.  Otherwise, returns an opaque
 value to be interpreted by the device pager.
 .Sh SEE ALSO
 .Xr bus_space 9
-.Sh HISTORY
-A
+.Sh AUTHOR
+The
 .Nm
-manual page appeared in
+interface was designed and implemented by Jason R. Thorpe of the
+Numerical Aerospace Simulation Facility, NASA Ames Research Center.
+Additional input on the
+.Nm
+design was provided by Chris Demetriou, Charles Hannum, Ross Harvey,
+Matthew Jacob, Jonathan Stone, and Matt Thomas.
+.Sh HISTORY
+The
+.Nm
+interface appeared in
 .Nx 1.3 .