[dma] Move I/O buffer DMA operations to iobuf.h

Include a potential DMA mapping within the definition of an I/O
buffer, and move all I/O buffer DMA mapping functions from dma.h to
iobuf.h.  This avoids the need for drivers to maintain a separate list
of DMA mappings for each I/O buffer that they may handle.

Network device drivers typically do not keep track of transmit I/O
buffers, since the network device core already maintains a transmit
queue.  Drivers will typically call netdev_tx_complete_next() to
complete a transmission without first obtaining the relevant I/O
buffer pointer (and will rely on the network device core automatically
cancelling any pending transmissions when the device is closed).

To allow this driver design approach to be retained, update the
netdev_tx_complete() family of functions to automatically perform the
DMA unmapping operation if required.  For symmetry, also update the
netdev_rx() family of functions to behave the same way.

As a further convenience for drivers, allow the network device core to
automatically perform DMA mapping on the transmit datapath before
calling the driver's transmit() method.  This avoids the need to
introduce a mapping error handling code path into the typically
error-free transmit methods.

With these changes, the modifications required to update a typical
network device driver to use the new DMA API are fairly minimal:

- Allocate and free descriptor rings and similar coherent structures
  using dma_alloc()/dma_free() rather than malloc_phys()/free_phys()

- Allocate and free receive buffers using alloc_rx_iob()/free_rx_iob()
  rather than alloc_iob()/free_iob()

- Calculate DMA addresses using dma() or iob_dma() rather than
  virt_to_bus()

- Set a 64-bit DMA mask if needed using dma_set_mask_64bit() and
  thereafter eliminate checks on DMA address ranges

- Either record the DMA device in netdev->dma, or call iob_map_tx() as
  part of the transmit() method

- Ensure that debug messages use virt_to_phys() when displaying
  "hardware" addresses

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

3 files changed, 61 insertions, 22 deletions

diff --git a/src/include/ipxe/dma.h b/src/include/ipxe/dma.h
index 842c9d6ef..b3fa24e47 100644
--- a/src/include/ipxe/dma.h
+++ b/src/include/ipxe/dma.h
@@ -12,7 +12,6 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #include <stdint.h>
 #include <ipxe/api.h>
 #include <ipxe/io.h>
-#include <ipxe/iobuf.h>
 #include <ipxe/malloc.h>
 #include <config/ioapi.h>
 
@@ -385,25 +384,4 @@ dma_set_mask_64bit ( struct dma_device *dma ) {
 	dma_set_mask ( dma, ~( ( physaddr_t ) 0 ) );
 }
 
-/**
- * Map I/O buffer for transmitting data to device
- *
- * @v dma		DMA device
- * @v map		DMA mapping to fill in
- * @v iobuf		I/O buffer
- * @ret rc		Return status code
- */
-static inline __always_inline int
-dma_map_tx_iob ( struct dma_device *dma, struct dma_mapping *map,
-		 struct io_buffer *iobuf ) {
-
-	/* Map I/O buffer */
-	return dma_map ( dma, map, virt_to_phys ( iobuf->data ),
-			 iob_len ( iobuf ), DMA_TX );
-}
-
-extern struct io_buffer * dma_alloc_rx_iob ( struct dma_device *dma,
-					     struct dma_mapping *map,
-					     size_t len );
-
 #endif /* _IPXE_DMA_H */
diff --git a/src/include/ipxe/iobuf.h b/src/include/ipxe/iobuf.h
index b40ade350..630a7753c 100644
--- a/src/include/ipxe/iobuf.h
+++ b/src/include/ipxe/iobuf.h
@@ -12,6 +12,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #include <stdint.h>
 #include <assert.h>
 #include <ipxe/list.h>
+#include <ipxe/dma.h>
 
 /**
  * Minimum I/O buffer length
@@ -38,6 +39,9 @@ struct io_buffer {
 	 */
 	struct list_head list;
 
+	/** DMA mapping */
+	struct dma_mapping map;
+
 	/** Start of the buffer */
 	void *head;
 	/** Start of data */
@@ -210,10 +214,61 @@ static inline void iob_populate ( struct io_buffer *iobuf,
 	(iobuf) = NULL;					\
 	__iobuf; } )
 
+/**
+ * Map I/O buffer for transmit DMA
+ *
+ * @v iobuf		I/O buffer
+ * @v dma		DMA device
+ * @ret rc		Return status code
+ */
+static inline __always_inline int iob_map_tx ( struct io_buffer *iobuf,
+					       struct dma_device *dma ) {
+	return dma_map ( dma, &iobuf->map, virt_to_phys ( iobuf->data ),
+			 iob_len ( iobuf ), DMA_TX );
+}
+
+/**
+ * Map empty I/O buffer for receive DMA
+ *
+ * @v iobuf		I/O buffer
+ * @v dma		DMA device
+ * @ret rc		Return status code
+ */
+static inline __always_inline int iob_map_rx ( struct io_buffer *iobuf,
+					       struct dma_device *dma ) {
+	assert ( iob_len ( iobuf ) == 0 );
+	return dma_map ( dma, &iobuf->map, virt_to_phys ( iobuf->data ),
+			 iob_tailroom ( iobuf ), DMA_RX );
+}
+
+/**
+ * Get I/O buffer DMA address
+ *
+ * @v iobuf		I/O buffer
+ * @ret addr		DMA address
+ */
+static inline __always_inline physaddr_t iob_dma ( struct io_buffer *iobuf ) {
+	return dma ( &iobuf->map, iobuf->data );
+}
+
+/**
+ * Unmap I/O buffer for DMA
+ *
+ * @v iobuf		I/O buffer
+ * @v dma		DMA device
+ * @ret rc		Return status code
+ */
+static inline __always_inline void iob_unmap ( struct io_buffer *iobuf ) {
+	dma_unmap ( &iobuf->map );
+}
+
 extern struct io_buffer * __malloc alloc_iob_raw ( size_t len, size_t align,
 						   size_t offset );
 extern struct io_buffer * __malloc alloc_iob ( size_t len );
 extern void free_iob ( struct io_buffer *iobuf );
+extern struct io_buffer * __malloc alloc_rx_iob ( size_t len,
+						  struct dma_device *dma );
+extern void free_rx_iob ( struct io_buffer *iobuf );
 extern void iob_pad ( struct io_buffer *iobuf, size_t min_len );
 extern int iob_ensure_headroom ( struct io_buffer *iobuf, size_t len );
 extern struct io_buffer * iob_concatenate ( struct list_head *list );
diff --git a/src/include/ipxe/netdevice.h b/src/include/ipxe/netdevice.h
index d498ab697..b9c651c71 100644
--- a/src/include/ipxe/netdevice.h
+++ b/src/include/ipxe/netdevice.h
@@ -246,6 +246,10 @@ struct net_device_operations {
 	 *
 	 * This method is guaranteed to be called only when the device
 	 * is open.
+	 *
+	 * If the network device has an associated DMA device, then
+	 * the I/O buffer will be automatically mapped for transmit
+	 * DMA.
 	 */
 	int ( * transmit ) ( struct net_device *netdev,
 			     struct io_buffer *iobuf );
@@ -358,6 +362,8 @@ struct net_device {
 	char name[NETDEV_NAME_LEN];
 	/** Underlying hardware device */
 	struct device *dev;
+	/** DMA device */
+	struct dma_device *dma;
 
 	/** Network device operations */
 	struct net_device_operations *op;