be2net: dma_sync each RX frag before passing it to the stack

The driver currently maps a page for DMA, divides the page into multiple
frags and posts them to the HW. It un-maps the page after data is received
on all the frags of the page. This scheme doesn't work when bounce buffers
are used for DMA (swiotlb=force kernel param).

This patch fixes this problem by calling dma_sync_single_for_cpu() for each
frag (excepting the last one) so that the data is copied from the bounce
buffers. The page is un-mapped only when DMA finishes on the last frag of
the page.
(Thanks Ben H. for suggesting the dma_sync API!)

This patch also renames the "last_page_user" field of be_rx_page_info{}
struct to "last_frag" to improve readability of the fixed code.

Reported-by: Li Fengmao <li.fengmao@zte.com.cn>
Signed-off-by: Sathya Perla <sathya.perla@emulex.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 24 insertions, 11 deletions

diff --git a/drivers/net/ethernet/emulex/benet/be.h b/drivers/net/ethernet/emulex/benet/be.h
index a150401a6cb3..bf5ca71df77f 100644
--- a/drivers/net/ethernet/emulex/benet/be.h
+++ b/drivers/net/ethernet/emulex/benet/be.h
@@ -261,9 +261,10 @@ struct be_tx_obj {
 /* Struct to remember the pages posted for rx frags */
 struct be_rx_page_info {
         struct page *page;
+        /* set to page-addr for last frag of the page & frag-addr otherwise */
         DEFINE_DMA_UNMAP_ADDR(bus);
         u16 page_offset;
-        bool last_page_user;
+        bool last_frag;         /* last frag of the page */
 };
 
 struct be_rx_stats {
diff --git a/drivers/net/ethernet/emulex/benet/be_main.c b/drivers/net/ethernet/emulex/benet/be_main.c
index 4f87f5c0b03c..34644969a4be 100644
--- a/drivers/net/ethernet/emulex/benet/be_main.c
+++ b/drivers/net/ethernet/emulex/benet/be_main.c
@@ -1448,11 +1448,15 @@ static struct be_rx_page_info *get_rx_page_info(struct be_rx_obj *rxo)
         rx_page_info = &rxo->page_info_tbl[frag_idx];
         BUG_ON(!rx_page_info->page);
 
-        if (rx_page_info->last_page_user) {
+        if (rx_page_info->last_frag) {
                 dma_unmap_page(&adapter->pdev->dev,
                                dma_unmap_addr(rx_page_info, bus),
                                adapter->big_page_size, DMA_FROM_DEVICE);
-                rx_page_info->last_page_user = false;
+                rx_page_info->last_frag = false;
+        } else {
+                dma_sync_single_for_cpu(&adapter->pdev->dev,
+                                        dma_unmap_addr(rx_page_info, bus),
+                                        rx_frag_size, DMA_FROM_DEVICE);
         }
 
         queue_tail_inc(rxq);
@@ -1786,17 +1790,16 @@ static void be_post_rx_frags(struct be_rx_obj *rxo, gfp_t gfp)
                                 rx_stats(rxo)->rx_post_fail++;
                                 break;
                         }
-                        page_info->page_offset = 0;
+                        page_offset = 0;
                 } else {
                         get_page(pagep);
-                        page_info->page_offset = page_offset + rx_frag_size;
+                        page_offset += rx_frag_size;
                 }
-                page_offset = page_info->page_offset;
+                page_info->page_offset = page_offset;
                 page_info->page = pagep;
-                dma_unmap_addr_set(page_info, bus, page_dmaaddr);
-                frag_dmaaddr = page_dmaaddr + page_info->page_offset;
 
                 rxd = queue_head_node(rxq);
+                frag_dmaaddr = page_dmaaddr + page_info->page_offset;
                 rxd->fragpa_lo = cpu_to_le32(frag_dmaaddr & 0xFFFFFFFF);
                 rxd->fragpa_hi = cpu_to_le32(upper_32_bits(frag_dmaaddr));
 
@@ -1804,15 +1807,24 @@ static void be_post_rx_frags(struct be_rx_obj *rxo, gfp_t gfp)
                 if ((page_offset + rx_frag_size + rx_frag_size) >
                                         adapter->big_page_size) {
                         pagep = NULL;
-                        page_info->last_page_user = true;
+                        page_info->last_frag = true;
+                        dma_unmap_addr_set(page_info, bus, page_dmaaddr);
+                } else {
+                        dma_unmap_addr_set(page_info, bus, frag_dmaaddr);
                 }
 
                 prev_page_info = page_info;
                 queue_head_inc(rxq);
                 page_info = &rxo->page_info_tbl[rxq->head];
         }
-        if (pagep)
-                prev_page_info->last_page_user = true;
+
+        /* Mark the last frag of a page when we break out of the above loop
+         * with no more slots available in the RXQ
+         */
+        if (pagep) {
+                prev_page_info->last_frag = true;
+                dma_unmap_addr_set(prev_page_info, bus, page_dmaaddr);
+        }
 
         if (posted) {
                 atomic_add(posted, &rxq->used);