From: Felix Fietkau <nbd@openwrt.org>
Date: Sun, 12 Apr 2015 11:59:47 +0200
Subject: [PATCH] bgmac: fix DMA rx corruption

The driver needs to inform the hardware about the first invalid (not yet
filled) rx slot, by writing its DMA descriptor pointer offset to the
BGMAC_DMA_RX_INDEX register.

This register was set to a value exceeding the rx ring size, effectively
allowing the hardware constant access to the full ring, regardless of
which slots are initialized.

Fix this by updating the register in bgmac_dma_rx_setup_desc.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
---

--- a/drivers/net/ethernet/broadcom/bgmac.c
+++ b/drivers/net/ethernet/broadcom/bgmac.c
@@ -362,6 +362,16 @@ static int bgmac_dma_rx_skb_for_slot(str
 	return 0;
 }
 
+static void bgmac_dma_rx_update_index(struct bgmac *bgmac,
+				      struct bgmac_dma_ring *ring)
+{
+	wmb();
+
+	bgmac_write(bgmac, ring->mmio_base + BGMAC_DMA_RX_INDEX,
+		    ring->index_base +
+		    ring->end * sizeof(struct bgmac_dma_desc));
+}
+
 static void bgmac_dma_rx_setup_desc(struct bgmac *bgmac,
 				    struct bgmac_dma_ring *ring, int desc_idx)
 {
@@ -380,6 +390,8 @@ static void bgmac_dma_rx_setup_desc(stru
 	dma_desc->addr_high = cpu_to_le32(upper_32_bits(ring->slots[desc_idx].dma_addr));
 	dma_desc->ctl0 = cpu_to_le32(ctl0);
 	dma_desc->ctl1 = cpu_to_le32(ctl1);
+
+	ring->end = (desc_idx + 1) % BGMAC_RX_RING_SLOTS;
 }
 
 static int bgmac_dma_rx_read(struct bgmac *bgmac, struct bgmac_dma_ring *ring,
@@ -394,9 +406,7 @@ static int bgmac_dma_rx_read(struct bgma
 	end_slot &= BGMAC_DMA_RX_STATDPTR;
 	end_slot /= sizeof(struct bgmac_dma_desc);
 
-	ring->end = end_slot;
-
-	while (ring->start != ring->end) {
+	while (ring->start != end_slot) {
 		struct device *dma_dev = bgmac->core->dma_dev;
 		struct bgmac_slot_info *slot = &ring->slots[ring->start];
 		struct bgmac_rx_header *rx = slot->buf + BGMAC_RX_BUF_OFFSET;
@@ -468,6 +478,8 @@ static int bgmac_dma_rx_read(struct bgma
 			break;
 	}
 
+	bgmac_dma_rx_update_index(bgmac, ring);
+
 	return handled;
 }
 
@@ -690,15 +702,12 @@ static void bgmac_dma_init(struct bgmac 
 		if (ring->unaligned)
 			bgmac_dma_rx_enable(bgmac, ring);
 
+		ring->start = 0;
+		ring->end = 0;
 		for (j = 0; j < ring->num_slots; j++)
 			bgmac_dma_rx_setup_desc(bgmac, ring, j);
 
-		bgmac_write(bgmac, ring->mmio_base + BGMAC_DMA_RX_INDEX,
-			    ring->index_base +
-			    ring->num_slots * sizeof(struct bgmac_dma_desc));
-
-		ring->start = 0;
-		ring->end = 0;
+		bgmac_dma_rx_update_index(bgmac, ring);
 	}
 }