[PATCH net-drivers-2.6 4/10] e1000: Delay clean-up of last Tx buffer

[Malli Chilakala <mallikarjuna.chilakala@xxxxxxxxx>]

4 Delay clean-up of last Tx buffer to fix pre-mature writeback of Tx 
descriptors.
Signed-off-by: Mallikarjuna R Chilakala <mallikarjuna.chilakala@xxxxxxxxx>
Signed-off-by: Ganesh Venkatesan <ganesh.venkatesan@xxxxxxxxx>
Signed-off-by: John Ronciak <john.ronciak@xxxxxxxxx>
diff -up net-drivers-2.6/drivers/net/e1000/e1000.h 
net-drivers-2.6/drivers/net/e1000.new/e1000.h
--- net-drivers-2.6/drivers/net/e1000/e1000.h   2005-02-01 23:10:24.986106336 
-0800
+++ net-drivers-2.6/drivers/net/e1000.new/e1000.h       2005-02-01 
23:10:26.474880008 -0800
@@ -209,6 +209,7 @@ struct e1000_adapter {
 
        /* TX */
        struct e1000_desc_ring tx_ring;
+       struct e1000_buffer previous_buffer_info;
        spinlock_t tx_lock;
        uint32_t txd_cmd;
        uint32_t tx_int_delay;
diff -up net-drivers-2.6/drivers/net/e1000/e1000_main.c 
net-drivers-2.6/drivers/net/e1000.new/e1000_main.c
--- net-drivers-2.6/drivers/net/e1000/e1000_main.c      2005-02-01 
23:10:24.989105880 -0800
+++ net-drivers-2.6/drivers/net/e1000.new/e1000_main.c  2005-02-01 
23:10:26.709844288 -0800
@@ -1103,6 +1103,7 @@ e1000_unmap_and_free_tx_resource(struct 
                        struct e1000_buffer *buffer_info)
 {
        struct pci_dev *pdev = adapter->pdev;
+
        if(buffer_info->dma) {
                pci_unmap_page(pdev,
                               buffer_info->dma,
@@ -1131,6 +1132,11 @@ e1000_clean_tx_ring(struct e1000_adapter
 
        /* Free all the Tx ring sk_buffs */
 
+       if (likely(adapter->previous_buffer_info.skb != NULL)) {
+               e1000_unmap_and_free_tx_resource(adapter, 
+                               &adapter->previous_buffer_info);
+       }
+
        for(i = 0; i < tx_ring->count; i++) {
                buffer_info = &tx_ring->buffer_info[i];
                e1000_unmap_and_free_tx_resource(adapter, buffer_info);
@@ -2214,11 +2220,34 @@ e1000_clean_tx_irq(struct e1000_adapter 
        eop_desc = E1000_TX_DESC(*tx_ring, eop);
 
        while(eop_desc->upper.data & cpu_to_le32(E1000_TXD_STAT_DD)) {
+               /* pre-mature writeback of Tx descriptors     */
+               /* clear (free buffers and unmap pci_mapping) */
+               /* previous_buffer_info                       */
+               if (likely(adapter->previous_buffer_info.skb != NULL)) {
+                       e1000_unmap_and_free_tx_resource(adapter, 
+                                       &adapter->previous_buffer_info);
+               }
+
                for(cleaned = FALSE; !cleaned; ) {
                        tx_desc = E1000_TX_DESC(*tx_ring, i);
                        buffer_info = &tx_ring->buffer_info[i];
+                       cleaned = (i == eop);
+
+                       /* pre-mature writeback of Tx descriptors */
+                       /* save the cleaning of the this for the  */
+                       /* next iteration                         */
+                       if (cleaned) {
+                               memcpy(&adapter->previous_buffer_info,
+                                       buffer_info,
+                                       sizeof(struct e1000_buffer));
+                               memset(buffer_info,
+                                       0,
+                                       sizeof(struct e1000_buffer));
+                       } else {
+                               e1000_unmap_and_free_tx_resource(adapter, 
+                                                       buffer_info);
+                       }
 
-                       e1000_unmap_and_free_tx_resource(adapter, buffer_info);
                        tx_desc->buffer_addr = 0;
                        tx_desc->lower.data = 0;
                        tx_desc->upper.data = 0;