[dma] Modify DMA API to simplify calculation of medial addresses

Redefine the value stored within a DMA mapping to be the offset
between physical addresses and DMA addresses within the mapped region.

Provide a dma() wrapper function to calculate the DMA address for any
pointer within a mapped region, thereby simplifying the use cases when
a device needs to be given addresses other than the region start
address.

On a platform using the "flat" DMA implementation the DMA offset for
any mapped region is always zero, with the result that dma_map() can
be optimised away completely and dma() reduces to a straightforward
call to virt_to_phys().

Signed-off-by: Michael Brown <mcb30@ipxe.org>

1 files changed, 64 insertions, 10 deletions

diff --git a/src/include/ipxe/dma.h b/src/include/ipxe/dma.h
index 878e03f11..0577493c7 100644
--- a/src/include/ipxe/dma.h
+++ b/src/include/ipxe/dma.h
@@ -30,8 +30,13 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 
 /** A DMA mapping */
 struct dma_mapping {
-	/** Device-side address */
-	physaddr_t addr;
+	/** Address offset
+	 *
+	 * This is the value that must be added to a physical address
+	 * within the mapping in order to produce the corresponding
+	 * device-side DMA address.
+	 */
+	physaddr_t offset;
 	/** Platform mapping token */
 	void *token;
 };
@@ -148,12 +153,10 @@ struct dma_operations {
  * @ret rc		Return status code
  */
 static inline __always_inline int
-DMAAPI_INLINE ( flat, dma_map ) ( struct dma_device *dma, physaddr_t addr,
+DMAAPI_INLINE ( flat, dma_map ) ( struct dma_device *dma,
+				  physaddr_t addr __unused,
 				  size_t len __unused, int flags __unused,
-				  struct dma_mapping *map ) {
-
-	/* Use physical address as device address */
-	map->addr = addr;
+				  struct dma_mapping *map __unused ) {
 
 	/* Increment mapping count (for debugging) */
 	if ( DBG_LOG )
@@ -187,13 +190,13 @@ DMAAPI_INLINE ( flat, dma_unmap ) ( struct dma_device *dma,
  * @ret addr		Buffer address, or NULL on error
  */
 static inline __always_inline void *
-DMAAPI_INLINE ( flat, dma_alloc ) ( struct dma_device *dma, size_t len,
-				    size_t align, struct dma_mapping *map ) {
+DMAAPI_INLINE ( flat, dma_alloc ) ( struct dma_device *dma,
+				    size_t len, size_t align,
+				    struct dma_mapping *map __unused ) {
 	void *addr;
 
 	/* Allocate buffer */
 	addr = malloc_phys ( len, align );
-	map->addr = virt_to_phys ( addr );
 
 	/* Increment allocation count (for debugging) */
 	if ( DBG_LOG && addr )
@@ -237,6 +240,35 @@ DMAAPI_INLINE ( flat, dma_set_mask ) ( struct dma_device *dma __unused,
 }
 
 /**
+ * Get DMA address from physical address
+ *
+ * @v map		DMA mapping
+ * @v addr		Physical address within the mapped region
+ * @ret addr		Device-side DMA address
+ */
+static inline __always_inline physaddr_t
+DMAAPI_INLINE ( flat, dma_phys ) ( struct dma_mapping *map __unused,
+				   physaddr_t addr ) {
+
+	/* Use physical address as device address */
+	return addr;
+}
+
+/**
+ * Get DMA address from physical address
+ *
+ * @v map		DMA mapping
+ * @v addr		Physical address within the mapped region
+ * @ret addr		Device-side DMA address
+ */
+static inline __always_inline physaddr_t
+DMAAPI_INLINE ( op, dma_phys ) ( struct dma_mapping *map, physaddr_t addr ) {
+
+	/* Adjust physical address using mapping offset */
+	return ( addr + map->offset );
+}
+
+/**
  * Map buffer for DMA
  *
  * @v dma		DMA device
@@ -289,6 +321,28 @@ void dma_free ( struct dma_device *dma, void *addr, size_t len,
 void dma_set_mask ( struct dma_device *dma, physaddr_t mask );
 
 /**
+ * Get DMA address from physical address
+ *
+ * @v map		DMA mapping
+ * @v addr		Physical address within the mapped region
+ * @ret addr		Device-side DMA address
+ */
+physaddr_t dma_phys ( struct dma_mapping *map, physaddr_t addr );
+
+/**
+ * Get DMA address from virtual address
+ *
+ * @v map		DMA mapping
+ * @v addr		Virtual address within the mapped region
+ * @ret addr		Device-side DMA address
+ */
+static inline __always_inline physaddr_t dma ( struct dma_mapping *map,
+					       void *addr ) {
+
+	return dma_phys ( map, virt_to_phys ( addr ) );
+}
+
+/**
  * Initialise DMA device
  *
  * @v dma		DMA device