[PATCH 1/3 v2] net/macb: increase RX buffer size for GEM

[Nicolas Ferre]

Macb Ethernet controller requires a RX buffer of 128 bytes. It is
highly sub-optimal for Gigabit-capable GEM that is able to use
a bigger DMA buffer. Change this constant and associated macros
with data stored in the private structure.
RX DMA buffer size has to be multiple of 64 bytes as indicated in
DMA Configuration Register specification.

Signed-off-by: Nicolas Ferre <nicolas.ferre at atmel.com>
---
 drivers/net/ethernet/cadence/macb.c | 45 ++++++++++++++++++++++++++++++-------
 drivers/net/ethernet/cadence/macb.h |  1 +
 2 files changed, 38 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c
index a9b0830..50f8669 100644
--- a/drivers/net/ethernet/cadence/macb.c
+++ b/drivers/net/ethernet/cadence/macb.c
@@ -32,7 +32,9 @@
 
 #include "macb.h"
 
-#define RX_BUFFER_SIZE		128
+#define MACB_RX_BUFFER_SIZE	128
+#define GEM_RX_BUFFER_SIZE	2048
+#define RX_BUFFER_MULTIPLE	64  /* bytes */
 #define RX_RING_SIZE		512 /* must be power of 2 */
 #define RX_RING_BYTES		(sizeof(struct macb_dma_desc) * RX_RING_SIZE)
 
@@ -92,7 +94,7 @@ static struct macb_dma_desc *macb_rx_desc(struct macb *bp, unsigned int index)
 
 static void *macb_rx_buffer(struct macb *bp, unsigned int index)
 {
-	return bp->rx_buffers + RX_BUFFER_SIZE * macb_rx_ring_wrap(index);
+	return bp->rx_buffers + bp->rx_buffer_size * macb_rx_ring_wrap(index);
 }
 
 void macb_set_hwaddr(struct macb *bp)
@@ -572,7 +574,7 @@ static int macb_rx_frame(struct macb *bp, unsigned int first_frag,
 	skb_put(skb, len);
 
 	for (frag = first_frag; ; frag++) {
-		unsigned int frag_len = RX_BUFFER_SIZE;
+		unsigned int frag_len = bp->rx_buffer_size;
 
 		if (offset + frag_len > len) {
 			BUG_ON(frag != last_frag);
@@ -580,7 +582,7 @@ static int macb_rx_frame(struct macb *bp, unsigned int first_frag,
 		}
 		skb_copy_to_linear_data_offset(skb, offset,
 				macb_rx_buffer(bp, frag), frag_len);
-		offset += RX_BUFFER_SIZE;
+		offset += bp->rx_buffer_size;
 		desc = macb_rx_desc(bp, frag);
 		desc->addr &= ~MACB_BIT(RX_USED);
 
@@ -860,6 +862,30 @@ static int macb_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	return NETDEV_TX_OK;
 }
 
+static void macb_init_rx_buffer_size(struct macb *bp)
+{
+	if (!macb_is_gem(bp)) {
+		bp->rx_buffer_size = MACB_RX_BUFFER_SIZE;
+	} else {
+		bp->rx_buffer_size = GEM_RX_BUFFER_SIZE;
+
+		if (bp->rx_buffer_size > PAGE_SIZE) {
+			netdev_warn(bp->dev,
+				    "RX buffer cannot be bigger than PAGE_SIZE, shrinking\n");
+			bp->rx_buffer_size = PAGE_SIZE;
+		}
+		if (bp->rx_buffer_size % RX_BUFFER_MULTIPLE) {
+			netdev_warn(bp->dev,
+				    "RX buffer must be multiple of %d bytes, shrinking\n",
+				    RX_BUFFER_MULTIPLE);
+			bp->rx_buffer_size =
+				rounddown(bp->rx_buffer_size, RX_BUFFER_MULTIPLE);
+		}
+		bp->rx_buffer_size = max(RX_BUFFER_MULTIPLE, GEM_RX_BUFFER_SIZE);
+	}
+}
+
+
 static void macb_free_consistent(struct macb *bp)
 {
 	if (bp->tx_skb) {
@@ -878,7 +904,7 @@ static void macb_free_consistent(struct macb *bp)
 	}
 	if (bp->rx_buffers) {
 		dma_free_coherent(&bp->pdev->dev,
-				  RX_RING_SIZE * RX_BUFFER_SIZE,
+				  RX_RING_SIZE * bp->rx_buffer_size,
 				  bp->rx_buffers, bp->rx_buffers_dma);
 		bp->rx_buffers = NULL;
 	}
@@ -911,7 +937,7 @@ static int macb_alloc_consistent(struct macb *bp)
 		   "Allocated TX ring of %d bytes at %08lx (mapped %p)\n",
 		   size, (unsigned long)bp->tx_ring_dma, bp->tx_ring);
 
-	size = RX_RING_SIZE * RX_BUFFER_SIZE;
+	size = RX_RING_SIZE * bp->rx_buffer_size;
 	bp->rx_buffers = dma_alloc_coherent(&bp->pdev->dev, size,
 					    &bp->rx_buffers_dma, GFP_KERNEL);
 	if (!bp->rx_buffers)
@@ -936,7 +962,7 @@ static void macb_init_rings(struct macb *bp)
 	for (i = 0; i < RX_RING_SIZE; i++) {
 		bp->rx_ring[i].addr = addr;
 		bp->rx_ring[i].ctrl = 0;
-		addr += RX_BUFFER_SIZE;
+		addr += bp->rx_buffer_size;
 	}
 	bp->rx_ring[RX_RING_SIZE - 1].addr |= MACB_BIT(RX_WRAP);
 
@@ -1046,7 +1072,7 @@ static void macb_configure_dma(struct macb *bp)
 
 	if (macb_is_gem(bp)) {
 		dmacfg = gem_readl(bp, DMACFG) & ~GEM_BF(RXBS, -1L);
-		dmacfg |= GEM_BF(RXBS, RX_BUFFER_SIZE / 64);
+		dmacfg |= GEM_BF(RXBS, bp->rx_buffer_size / RX_BUFFER_MULTIPLE);
 		dmacfg |= GEM_BF(FBLDO, 16);
 		dmacfg |= GEM_BIT(TXPBMS) | GEM_BF(RXBMS, -1L);
 		gem_writel(bp, DMACFG, dmacfg);
@@ -1221,6 +1247,9 @@ static int macb_open(struct net_device *dev)
 	if (!bp->phy_dev)
 		return -EAGAIN;
 
+	/* RX buffers initialization */
+	macb_init_rx_buffer_size(bp);
+
 	err = macb_alloc_consistent(bp);
 	if (err) {
 		netdev_err(dev, "Unable to allocate DMA memory (error %d)\n",
diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
index 570908b..2681455 100644
--- a/drivers/net/ethernet/cadence/macb.h
+++ b/drivers/net/ethernet/cadence/macb.h
@@ -544,6 +544,7 @@ struct macb {
 	unsigned int		rx_tail;
 	struct macb_dma_desc	*rx_ring;
 	void			*rx_buffers;
+	size_t			rx_buffer_size;
 
 	unsigned int		tx_head, tx_tail;
 	struct macb_dma_desc	*tx_ring;
-- 
1.8.0