From: Fuyun Liang <liangfuyun1@huawei.com>
Date: Tue, 16 Oct 2018 19:58:52 +0800
Subject: net: hns3: fix for multiple unmapping DMA problem
Patch-mainline: v4.20-rc1
Git-commit: bcdb12b70c5266a78430a248e57c8c122839b951
References: bsc#1104353 FATE#326415

When sending a big fragment using multiple buffer descriptor,
hns3 does one maping, but do multiple unmapping when tx is done,
which may cause unmapping problem.

To fix it, this patch makes sure the value of desc_cb.length of
the non-first bd is zero. If desc_cb.length is zero, we do not
unmap the buffer.

Fixes: 76ad4f0ee747 ("net: hns3: Add support of HNS3 Ethernet Driver for hip08 SoC")
Signed-off-by: Fuyun Liang <liangfuyun1@huawei.com>
Signed-off-by: Peng Li <lipeng321@huawei.com>
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/ethernet/hisilicon/hns3/hns3_enet.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

--- a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
+++ b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
@@ -1051,6 +1051,8 @@ static int hns3_fill_desc(struct hns3_en
 		return -ENOMEM;
 	}
 
+	desc_cb->length = size;
+
 	frag_buf_num = (size + HNS3_MAX_BD_SIZE - 1) / HNS3_MAX_BD_SIZE;
 	sizeoflast = size % HNS3_MAX_BD_SIZE;
 	sizeoflast = sizeoflast ? sizeoflast : HNS3_MAX_BD_SIZE;
@@ -1059,15 +1061,14 @@ static int hns3_fill_desc(struct hns3_en
 	for (k = 0; k < frag_buf_num; k++) {
 		/* The txbd's baseinfo of DESC_TYPE_PAGE & DESC_TYPE_SKB */
 		desc_cb->priv = priv;
-		desc_cb->length = (k == frag_buf_num - 1) ?
-					sizeoflast : HNS3_MAX_BD_SIZE;
 		desc_cb->dma = dma + HNS3_MAX_BD_SIZE * k;
 		desc_cb->type = (type == DESC_TYPE_SKB && !k) ?
 					DESC_TYPE_SKB : DESC_TYPE_PAGE;
 
 		/* now, fill the descriptor */
 		desc->addr = cpu_to_le64(dma + HNS3_MAX_BD_SIZE * k);
-		desc->tx.send_size = cpu_to_le16((u16)desc_cb->length);
+		desc->tx.send_size = cpu_to_le16((k == frag_buf_num - 1) ?
+				(u16)sizeoflast : (u16)HNS3_MAX_BD_SIZE);
 		hns3_set_txbd_baseinfo(&bdtp_fe_sc_vld_ra_ri,
 				       frag_end && (k == frag_buf_num - 1) ?
 						1 : 0);
@@ -1150,12 +1151,14 @@ static void hns3_clear_desc(struct hns3_
 					 ring->desc_cb[ring->next_to_use].dma,
 					ring->desc_cb[ring->next_to_use].length,
 					DMA_TO_DEVICE);
-		else
+		else if (ring->desc_cb[ring->next_to_use].length)
 			dma_unmap_page(dev,
 				       ring->desc_cb[ring->next_to_use].dma,
 				       ring->desc_cb[ring->next_to_use].length,
 				       DMA_TO_DEVICE);
 
+		ring->desc_cb[ring->next_to_use].length = 0;
+
 		/* rollback one */
 		ring_ptr_move_bw(ring, next_to_use);
 	}
@@ -1874,7 +1877,7 @@ static void hns3_unmap_buffer(struct hns
 	if (cb->type == DESC_TYPE_SKB)
 		dma_unmap_single(ring_to_dev(ring), cb->dma, cb->length,
 				 ring_to_dma_dir(ring));
-	else
+	else if (cb->length)
 		dma_unmap_page(ring_to_dev(ring), cb->dma, cb->length,
 			       ring_to_dma_dir(ring));
 }