dpaa_eth: Fix pool counters on error path

When system memory is depleted, the Rx buffers are put back into
their pool. Bad accounting on that error path made it so the software
software counters remained behind the hardware counters, eventually
allowing for negative totals.
Fix this and keep the software pool counters in sync with the hardware
counters.

Signed-off-by: Ioana Radulescu <ruxandra.radulescu@freescale.com>
Signed-off-by: Bogdan Hamciuc <bogdan.hamciuc@freescale.com>
Change-Id: I46191bc38f12aa6a25378eba3e5891bc3f18cbc6
Reviewed-on: http://git.am.freescale.net:8181/3049
Tested-by: Review Code-CDREVIEW <CDREVIEW@freescale.com>
Reviewed-by: Sovaiala Cristian-Constantin-B39531 <Cristian.Sovaiala@freescale.com>
Reviewed-by: Bucur Madalin-Cristian-B32716 <madalin.bucur@freescale.com>
Reviewed-by: Fleming Andrew-AFLEMING <AFLEMING@freescale.com>

1 files changed, 37 insertions, 19 deletions

diff --git a/drivers/net/ethernet/freescale/dpa/dpaa_eth_sg.c b/drivers/net/ethernet/freescale/dpa/dpaa_eth_sg.c
index a47dfab..f93c346 100644
--- a/drivers/net/ethernet/freescale/dpa/dpaa_eth_sg.c
+++ b/drivers/net/ethernet/freescale/dpa/dpaa_eth_sg.c
@@ -45,22 +45,6 @@
 #ifdef CONFIG_FSL_DPAA_ETH_SG_SUPPORT
 #define DPA_SGT_MAX_ENTRIES 16 /* maximum number of entries in SG Table */
 
-/*
- * It does not return a page as you get the page from the fd,
- * this is only for refcounting and DMA unmapping
- */
-static inline void dpa_bp_removed_one_page(struct dpa_bp *dpa_bp,
-					   dma_addr_t dma_addr)
-{
-	int *count_ptr;
-
-	count_ptr = __this_cpu_ptr(dpa_bp->percpu_count);
-	(*count_ptr)--;
-
-	dma_unmap_single(dpa_bp->dev, dma_addr, dpa_bp->size,
-		DMA_BIDIRECTIONAL);
-}
-
 /* DMA map and add a page into the bpool */
 static void dpa_bp_add_page(struct dpa_bp *dpa_bp, unsigned long vaddr)
 {
@@ -331,6 +315,7 @@ static struct sk_buff *__hot sg_fd_to_skb(const struct dpa_priv_s *priv,
 	int i;
 	const t_FmPrsResult *parse_results;
 	struct sk_buff *skb = NULL;
+	int *count_ptr;
 
 	vaddr = phys_to_virt(addr);
 #ifdef CONFIG_FSL_DPAA_1588
@@ -351,21 +336,33 @@ static struct sk_buff *__hot sg_fd_to_skb(const struct dpa_priv_s *priv,
 
 		dpa_bp = dpa_bpid2pool(sgt[i].bpid);
 		BUG_ON(IS_ERR(dpa_bp));
+		count_ptr = __this_cpu_ptr(dpa_bp->percpu_count);
 
 		sg_addr = qm_sg_addr(&sgt[i]);
 		sg_vaddr = phys_to_virt(sg_addr);
 
-		dpa_bp_removed_one_page(dpa_bp, sg_addr);
-
 		if (i == 0) {
+			/* Tentatively access the first buffer, but don't unmap
+			 * it until we're certain the skb allocation succeeds.
+			 */
+			dma_sync_single_for_cpu(dpa_bp->dev, sg_addr,
+				dpa_bp->size, DMA_BIDIRECTIONAL);
+
 			/* This is the first S/G entry, so build the skb
 			 * around its data buffer
 			 */
 			skb = build_skb(sg_vaddr,
 					dpa_bp->size + DPA_SKB_TAILROOM);
 			if (unlikely(!skb))
+				/* dpa_fd_release() will put the current frame
+				 * back into the pool. DMA mapping status has
+				 * not changed, nor have the pool counts.
+				 */
 				return NULL;
 
+			dma_unmap_single(dpa_bp->dev, sg_addr, dpa_bp->size,
+				DMA_BIDIRECTIONAL);
+
 			/* In the case of a SG frame, FMan stores the Internal
 			 * Context in the buffer containing the sgt.
 			 * Inspect the parse results before anything else.
@@ -382,6 +379,8 @@ static struct sk_buff *__hot sg_fd_to_skb(const struct dpa_priv_s *priv,
 				dpa_get_rx_extra_headroom());
 			skb_put(skb, sgt[i].length);
 		} else {
+			dma_unmap_single(dpa_bp->dev, sg_addr, dpa_bp->size,
+				DMA_BIDIRECTIONAL);
 			/*
 			 * Not the first S/G entry; all data from buffer will
 			 * be added in an skb fragment; fragment index is offset
@@ -398,6 +397,8 @@ static struct sk_buff *__hot sg_fd_to_skb(const struct dpa_priv_s *priv,
 			skb_add_rx_frag(skb, i - 1, page, frag_offset, frag_len,
 					frag_len);
 		}
+		/* Update the pool count for the current {cpu x bpool} */
+		(*count_ptr)--;
 
 		if (sgt[i].final)
 			break;
@@ -423,6 +424,7 @@ void __hot _dpa_rx(struct net_device *net_dev,
 	unsigned int skb_len;
 	struct rtnl_link_stats64 *percpu_stats = &percpu_priv->stats;
 	int use_gro = net_dev->features & NETIF_F_GRO;
+	int *count_ptr;
 
 	if (unlikely(fd_status & FM_FD_STAT_ERRORS) != 0) {
 		if (netif_msg_hw(priv) && net_ratelimit())
@@ -434,7 +436,13 @@ void __hot _dpa_rx(struct net_device *net_dev,
 	}
 
 	dpa_bp = dpa_bpid2pool(fd->bpid);
-	dpa_bp_removed_one_page(dpa_bp, addr);
+	count_ptr = __this_cpu_ptr(dpa_bp->percpu_count);
+	/* Prepare to read from the buffer, but don't unmap it until
+	 * we know the skb allocation succeeded. At this point we already
+	 * own the buffer - i.e. FMan won't access it anymore.
+	 */
+	dma_sync_single_for_cpu(dpa_bp->dev, addr, dpa_bp->size,
+		DMA_BIDIRECTIONAL);
 
 	/* prefetch the first 64 bytes of the frame or the SGT start */
 	prefetch(phys_to_virt(addr) + dpa_fd_offset(fd));
@@ -447,8 +455,18 @@ void __hot _dpa_rx(struct net_device *net_dev,
 		/* The only FD types that we may receive are contig and S/G */
 		BUG();
 	if (unlikely(!skb))
+		/* We haven't yet touched the DMA mapping or the pool count;
+		 * dpa_fd_release() will just put the buffer back in the pool
+		 */
 		goto _release_frame;
 
+	/* Account for either the contig buffer or the SGT buffer (depending on
+	 * which case we were in) having been removed from the pool.
+	 * Also, permanently unmap the buffer.
+	 */
+	(*count_ptr)--;
+	dma_unmap_single(dpa_bp->dev, addr, dpa_bp->size, DMA_BIDIRECTIONAL);
+
 	skb->protocol = eth_type_trans(skb, net_dev);
 
 	/* IP Reassembled frames are allowed to be larger than MTU */