u8 css, cso;
 
        if (likely(skb->ip_summed == CHECKSUM_PARTIAL)) {
-               cso = skb_transport_offset(skb);
-               css = cso + skb->csum_offset;
-               if (unlikely(cso & 0x1)) {
+               css = (u8) (skb->csum_start - skb_headroom(skb));
+               cso = css + (u8) skb->csum_offset;
+               if (unlikely(css & 0x1)) {
+                       /* L1 hardware requires an even number here */
                        dev_printk(KERN_DEBUG, &adapter->pdev->dev,
                                "payload offset not an even number\n");
                        return -1;
                }
-               ptpd->word3 |= (cso & TPD_PLOADOFFSET_MASK) <<
+               ptpd->word3 |= (css & TPD_PLOADOFFSET_MASK) <<
                        TPD_PLOADOFFSET_SHIFT;
-               ptpd->word3 |= (css & TPD_CCSUMOFFSET_MASK) <<
+               ptpd->word3 |= (cso & TPD_CCSUMOFFSET_MASK) <<
                        TPD_CCSUMOFFSET_SHIFT;
                ptpd->word3 |= 1 << TPD_CUST_CSUM_EN_SHIFT;
                return true;