net: macb: Add page pool support handle multi-descriptor frame rx

Use the page pool allocator for the data buffers and enable skb
recycling support, instead of relying on netdev_alloc_skb
allocating the entire skb during the refill.

The patch also add support for receiving network frames that span
multiple DMA descriptors in the Cadence MACB/GEM Ethernet driver.

The patch removes the requirement that limited frame reception to
a single descriptor (RX_SOF && RX_EOF), also avoiding potential
contiguous multi-page allocation for large frames.

Signed-off-by: Paolo Valerio <pvalerio@redhat.com>

Author: vlrpl

drivers/net/ethernet/cadence/Kconfig

@@ -25,6 +25,7 @@ config MACB
 	depends on PTP_1588_CLOCK_OPTIONAL
 	select PHYLINK
 	select CRC32
+	select PAGE_POOL
 	help
 	  The Cadence MACB ethernet interface is found on many Atmel AT32 and
 	  AT91 parts.  This driver also supports the Cadence GEM (Gigabit

drivers/net/ethernet/cadence/macb.h

@@ -14,6 +14,7 @@
 #include <linux/interrupt.h>
 #include <linux/phy/phy.h>
 #include <linux/workqueue.h>
+#include <net/page_pool/helpers.h>
 
 #if defined(CONFIG_ARCH_DMA_ADDR_T_64BIT) || defined(CONFIG_MACB_USE_HWSTAMP)
 #define MACB_EXT_DESC
@@ -1305,6 +1306,8 @@ struct macb_queue {
 	void			*rx_buffers;
 	struct napi_struct	napi_rx;
 	struct queue_stats stats;
+	struct page_pool	*page_pool;
+	struct sk_buff		*skb;
 };
 
 struct ethtool_rx_fs_item {
@@ -1328,6 +1331,8 @@ struct macb {
 	struct macb_dma_desc	*rx_ring_tieoff;
 	dma_addr_t		rx_ring_tieoff_dma;
 	size_t			rx_buffer_size;
+	size_t			rx_headroom;
+	unsigned int		rx_ip_align;
 
 	unsigned int		rx_ring_size;
 	unsigned int		tx_ring_size;