[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>

7 files changed, 100 insertions, 58 deletions

diff --git a/src/core/dma.c b/src/core/dma.c
index 9fc0c5453..3bf6957b9 100644
--- a/src/core/dma.c
+++ b/src/core/dma.c
@@ -46,6 +46,7 @@ PROVIDE_DMAAPI_INLINE ( flat, dma_unmap );
 PROVIDE_DMAAPI_INLINE ( flat, dma_alloc );
 PROVIDE_DMAAPI_INLINE ( flat, dma_free );
 PROVIDE_DMAAPI_INLINE ( flat, dma_set_mask );
+PROVIDE_DMAAPI_INLINE ( flat, dma_phys );
 
 /******************************************************************************
  *
@@ -138,6 +139,7 @@ PROVIDE_DMAAPI ( op, dma_unmap, dma_op_unmap );
 PROVIDE_DMAAPI ( op, dma_alloc, dma_op_alloc );
 PROVIDE_DMAAPI ( op, dma_free, dma_op_free );
 PROVIDE_DMAAPI ( op, dma_set_mask, dma_op_set_mask );
+PROVIDE_DMAAPI_INLINE ( op, dma_phys );
 
 /******************************************************************************
  *
diff --git a/src/drivers/net/intel.c b/src/drivers/net/intel.c
index 408101bad..5c6dc2143 100644
--- a/src/drivers/net/intel.c
+++ b/src/drivers/net/intel.c
@@ -513,7 +513,7 @@ int intel_create_ring ( struct intel_nic *intel, struct intel_ring *ring ) {
 	memset ( ring->desc, 0, ring->len );
 
 	/* Program ring address */
-	address = ring->map.addr;
+	address = dma ( &ring->map, ring->desc );
 	writel ( ( address & 0xffffffffUL ),
 		 ( intel->regs + ring->reg + INTEL_xDBAL ) );
 	if ( sizeof ( physaddr_t ) > sizeof ( uint32_t ) ) {
@@ -571,7 +571,6 @@ void intel_refill_rx ( struct intel_nic *intel ) {
 	struct dma_mapping *map;
 	unsigned int rx_idx;
 	unsigned int rx_tail;
-	physaddr_t address;
 	unsigned int refilled = 0;
 
 	/* Refill ring */
@@ -596,8 +595,7 @@ void intel_refill_rx ( struct intel_nic *intel ) {
 		intel->rx.ring.prod++;
 
 		/* Populate receive descriptor */
-		address = map->addr;
-		intel->rx.ring.describe ( rx, address, 0 );
+		intel->rx.ring.describe ( rx, dma ( map, iobuf->data ), 0 );
 
 		DBGC2 ( intel, "INTEL %p RX %d is [%lx,%lx)\n",
 			intel, rx_idx, virt_to_phys ( iobuf->data ),
@@ -762,7 +760,6 @@ int intel_transmit ( struct net_device *netdev, struct io_buffer *iobuf ) {
 	struct dma_mapping *map;
 	unsigned int tx_idx;
 	unsigned int tx_tail;
-	physaddr_t address;
 	size_t len;
 	int rc;
 
@@ -783,9 +780,8 @@ int intel_transmit ( struct net_device *netdev, struct io_buffer *iobuf ) {
 	intel->tx.ring.prod++;
 
 	/* Populate transmit descriptor */
-	address = map->addr;
 	len = iob_len ( iobuf );
-	intel->tx.ring.describe ( tx, address, len );
+	intel->tx.ring.describe ( tx, dma ( map, iobuf->data ), len );
 	wmb();
 
 	/* Notify card that there are packets ready to transmit */
diff --git a/src/drivers/net/intelxl.c b/src/drivers/net/intelxl.c
index 14a5858f3..0808c784a 100644
--- a/src/drivers/net/intelxl.c
+++ b/src/drivers/net/intelxl.c
@@ -152,7 +152,8 @@ int intelxl_msix_enable ( struct intelxl_nic *intelxl,
 	}
 
 	/* Configure interrupt zero to write to dummy location */
-	pci_msix_map ( &intelxl->msix.cap, 0, intelxl->msix.map.addr, 0 );
+	pci_msix_map ( &intelxl->msix.cap, 0,
+		       dma ( &intelxl->msix.map, &intelxl->msix.msg ), 0 );
 
 	/* Enable dummy interrupt zero */
 	pci_msix_unmask ( &intelxl->msix.cap, 0 );
@@ -231,22 +232,6 @@ static int intelxl_alloc_admin ( struct intelxl_nic *intelxl,
 }
 
 /**
- * Get DMA address for admin descriptor or buffer entry
- *
- * @v admin		Admin queue
- * @v addr		Virtual address
- * @ret addr		DMA address
- */
-static physaddr_t intelxl_admin_address ( struct intelxl_admin *admin,
-					  void *addr ) {
-	size_t offset;
-
-	/* Calculate offset within mapped area */
-	offset = ( addr - ( ( void * ) admin->buf ) );
-	return ( admin->map.addr + offset );
-}
-
-/**
  * Enable admin queue
  *
  * @v intelxl		Intel device
@@ -270,7 +255,7 @@ static void intelxl_enable_admin ( struct intelxl_nic *intelxl,
 	admin->index = 0;
 
 	/* Program queue address */
-	address = intelxl_admin_address ( admin, admin->desc );
+	address = dma ( &admin->map, admin->desc );
 	writel ( ( address & 0xffffffffUL ), admin_regs + regs->bal );
 	if ( sizeof ( physaddr_t ) > sizeof ( uint32_t ) ) {
 		writel ( ( ( ( uint64_t ) address ) >> 32 ),
@@ -365,7 +350,7 @@ static void intelxl_admin_event_init ( struct intelxl_nic *intelxl,
 	/* Initialise descriptor */
 	evt = &admin->desc[ index % INTELXL_ADMIN_NUM_DESC ];
 	buf = &admin->buf[ index % INTELXL_ADMIN_NUM_DESC ];
-	address = intelxl_admin_address ( admin, buf );
+	address = dma ( &admin->map, buf );
 	evt->flags = cpu_to_le16 ( INTELXL_ADMIN_FL_BUF );
 	evt->len = cpu_to_le16 ( sizeof ( *buf ) );
 	evt->params.buffer.high = cpu_to_le32 ( address >> 32 );
@@ -410,7 +395,7 @@ int intelxl_admin_command ( struct intelxl_nic *intelxl ) {
 
 	/* Populate data buffer address if applicable */
 	if ( cmd->flags & cpu_to_le16 ( INTELXL_ADMIN_FL_BUF ) ) {
-		address = intelxl_admin_address ( admin, buf );
+		address = dma ( &admin->map, buf );
 		cmd->params.buffer.high = cpu_to_le32 ( address >> 32 );
 		cmd->params.buffer.low = cpu_to_le32 ( address & 0xffffffffUL );
 	}
@@ -1267,6 +1252,7 @@ static int intelxl_disable_ring ( struct intelxl_nic *intelxl,
  */
 static int intelxl_create_ring ( struct intelxl_nic *intelxl,
 				 struct intelxl_ring *ring ) {
+	physaddr_t address;
 	int rc;
 
 	/* Allocate descriptor ring */
@@ -1274,7 +1260,8 @@ static int intelxl_create_ring ( struct intelxl_nic *intelxl,
 		goto err_alloc;
 
 	/* Program queue context */
-	if ( ( rc = ring->context ( intelxl, ring->map.addr ) ) != 0 )
+	address = dma ( &ring->map, ring->desc.raw );
+	if ( ( rc = ring->context ( intelxl, address ) ) != 0 )
 		goto err_context;
 
 	/* Enable ring */
@@ -1346,7 +1333,7 @@ static void intelxl_refill_rx ( struct intelxl_nic *intelxl ) {
 		intelxl->rx.ring.prod++;
 
 		/* Populate receive descriptor */
-		rx->address = cpu_to_le64 ( map->addr );
+		rx->address = cpu_to_le64 ( dma ( map, iobuf->data ) );
 		rx->flags = 0;
 
 		DBGC2 ( intelxl, "INTELXL %p RX %d is [%08lx,%08lx)\n",
@@ -1537,7 +1524,7 @@ int intelxl_transmit ( struct net_device *netdev, struct io_buffer *iobuf ) {
 
 	/* Populate transmit descriptor */
 	len = iob_len ( iobuf );
-	tx->address = cpu_to_le64 ( map->addr );
+	tx->address = cpu_to_le64 ( dma ( map, iobuf->data ) );
 	tx->len = cpu_to_le32 ( INTELXL_TX_DATA_LEN ( len ) );
 	tx->flags = cpu_to_le32 ( INTELXL_TX_DATA_DTYP | INTELXL_TX_DATA_EOP |
 				  INTELXL_TX_DATA_RS | INTELXL_TX_DATA_JFDI );
diff --git a/src/drivers/net/intelxlvf.c b/src/drivers/net/intelxlvf.c
index 61ac5e5c0..f944b4daa 100644
--- a/src/drivers/net/intelxlvf.c
+++ b/src/drivers/net/intelxlvf.c
@@ -380,12 +380,14 @@ static int intelxlvf_admin_configure ( struct net_device *netdev ) {
 	buf->cfg.count = cpu_to_le16 ( 1 );
 	buf->cfg.tx.vsi = cpu_to_le16 ( intelxl->vsi );
 	buf->cfg.tx.count = cpu_to_le16 ( INTELXL_TX_NUM_DESC );
-	buf->cfg.tx.base = cpu_to_le64 ( intelxl->tx.ring.map.addr );
+	buf->cfg.tx.base = cpu_to_le64 ( dma ( &intelxl->tx.ring.map,
+					       intelxl->tx.ring.desc.raw ) );
 	buf->cfg.rx.vsi = cpu_to_le16 ( intelxl->vsi );
 	buf->cfg.rx.count = cpu_to_le32 ( INTELXL_RX_NUM_DESC );
 	buf->cfg.rx.len = cpu_to_le32 ( intelxl->mfs );
 	buf->cfg.rx.mfs = cpu_to_le32 ( intelxl->mfs );
-	buf->cfg.rx.base = cpu_to_le64 ( intelxl->rx.ring.map.addr );
+	buf->cfg.rx.base = cpu_to_le64 ( dma ( &intelxl->rx.ring.map,
+					       intelxl->rx.ring.desc.raw ) );
 
 	/* Issue command */
 	if ( ( rc = intelxlvf_admin_command ( netdev ) ) != 0 )
diff --git a/src/drivers/net/realtek.c b/src/drivers/net/realtek.c
index 0f3038d36..bca52266f 100644
--- a/src/drivers/net/realtek.c
+++ b/src/drivers/net/realtek.c
@@ -506,6 +506,7 @@ static void realtek_check_link ( struct net_device *netdev ) {
  * @ret rc		Return status code
  */
 static int realtek_create_buffer ( struct realtek_nic *rtl ) {
+	struct realtek_rx_buffer *rxbuf = &rtl->rxbuf;
 	size_t len = ( RTL_RXBUF_LEN + RTL_RXBUF_PAD );
 
 	/* Do nothing unless in legacy mode */
@@ -513,17 +514,16 @@ static int realtek_create_buffer ( struct realtek_nic *rtl ) {
 		return 0;
 
 	/* Allocate buffer */
-	rtl->rxbuf.data = dma_alloc ( rtl->dma, len, RTL_RXBUF_ALIGN,
-				      &rtl->rxbuf.map );
-	if ( ! rtl->rxbuf.data )
+	rxbuf->data = dma_alloc ( rtl->dma, len, RTL_RXBUF_ALIGN, &rxbuf->map );
+	if ( ! rxbuf->data )
 		return -ENOMEM;
 
 	/* Program buffer address */
-	writel ( rtl->rxbuf.map.addr, rtl->regs + RTL_RBSTART );
+	writel ( dma ( &rxbuf->map, rxbuf->data ), rtl->regs + RTL_RBSTART );
 	DBGC ( rtl, "REALTEK %p receive buffer is at [%08lx,%08lx,%08lx)\n",
-	       rtl, virt_to_phys ( rtl->rxbuf.data ),
-	       ( virt_to_phys ( rtl->rxbuf.data ) + RTL_RXBUF_LEN ),
-	       ( virt_to_phys ( rtl->rxbuf.data ) + len ) );
+	       rtl, virt_to_phys ( rxbuf->data ),
+	       ( virt_to_phys ( rxbuf->data ) + RTL_RXBUF_LEN ),
+	       ( virt_to_phys ( rxbuf->data ) + len ) );
 
 	return 0;
 }
@@ -534,6 +534,7 @@ static int realtek_create_buffer ( struct realtek_nic *rtl ) {
  * @v rtl		Realtek device
  */
 static void realtek_destroy_buffer ( struct realtek_nic *rtl ) {
+	struct realtek_rx_buffer *rxbuf = &rtl->rxbuf;
 	size_t len = ( RTL_RXBUF_LEN + RTL_RXBUF_PAD );
 
 	/* Do nothing unless in legacy mode */
@@ -544,9 +545,9 @@ static void realtek_destroy_buffer ( struct realtek_nic *rtl ) {
 	writel ( 0, rtl->regs + RTL_RBSTART );
 
 	/* Free buffer */
-	dma_free ( rtl->dma, rtl->rxbuf.data, len, &rtl->rxbuf.map );
-	rtl->rxbuf.data = NULL;
-	rtl->rxbuf.offset = 0;
+	dma_free ( rtl->dma, rxbuf->data, len, &rxbuf->map );
+	rxbuf->data = NULL;
+	rxbuf->offset = 0;
 }
 
 /**
@@ -574,7 +575,7 @@ static int realtek_create_ring ( struct realtek_nic *rtl,
 	memset ( ring->desc, 0, ring->len );
 
 	/* Program ring address */
-	address = ring->map.addr;
+	address = dma ( &ring->map, ring->desc );
 	writel ( ( ( ( uint64_t ) address ) >> 32 ),
 		 rtl->regs + ring->reg + 4 );
 	writel ( ( address & 0xffffffffUL ), rtl->regs + ring->reg );
@@ -648,7 +649,7 @@ static void realtek_refill_rx ( struct realtek_nic *rtl ) {
 		rtl->rx.ring.prod++;
 
 		/* Populate receive descriptor */
-		rx->address = cpu_to_le64 ( map->addr );
+		rx->address = cpu_to_le64 ( dma ( map, iobuf->data ) );
 		rx->length = cpu_to_le16 ( RTL_RX_MAX_LEN );
 		wmb();
 		rx->flags = ( cpu_to_le16 ( RTL_DESC_OWN ) |
@@ -797,7 +798,7 @@ static int realtek_transmit ( struct net_device *netdev,
 	/* Map I/O buffer */
 	if ( ( rc = dma_map_tx_iob ( rtl->dma, iobuf, map ) ) != 0 )
 		return rc;
-	address = map->addr;
+	address = dma ( map, iobuf->data );
 
 	/* Update producer index */
 	rtl->tx.ring.prod++;
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
diff --git a/src/interface/efi/efi_pci.c b/src/interface/efi/efi_pci.c
index 6c6ac5c77..e33a8980d 100644
--- a/src/interface/efi/efi_pci.c
+++ b/src/interface/efi/efi_pci.c
@@ -335,7 +335,7 @@ static int efipci_dma_map ( struct dma_device *dma, physaddr_t addr, size_t len,
 	int rc;
 
 	/* Sanity check */
-	assert ( map->addr == 0 );
+	assert ( map->offset == 0 );
 	assert ( map->token == NULL );
 
 	/* Determine operation */
@@ -374,7 +374,7 @@ static int efipci_dma_map ( struct dma_device *dma, physaddr_t addr, size_t len,
 	}
 
 	/* Populate mapping */
-	map->addr = bus;
+	map->offset = ( bus - addr );
 	map->token = mapping;
 
 	/* Increment mapping count (for debugging) */
@@ -408,7 +408,7 @@ static void efipci_dma_unmap ( struct dma_device *dma,
 	pci_io->Unmap ( pci_io, map->token );
 
 	/* Clear mapping */
-	map->addr = 0;
+	map->offset = 0;
 	map->token = NULL;
 
 	/* Decrement mapping count (for debugging) */