iwlwifi: dma mapping read and write changes

When iwlwifi runs on IOMMU, IOMMU generates a lot of PTE write faults
because PTE write bit is not set on some of PTE's. This is because iwlwifi
driver calls DMA mapping with PCI_DMA_TODEVICE which is read only in mapping
PTE. But iwlwifi device actually writes to the mapped page to update its contents.
This issue is not exposed in swiotlb. But VT-d hardware can capture this fault and
stop the fault transaction.

The iwl TX command contains a scratch field that is updated by uCode to
indicate retry counts. For 5000 series the patch is required also for
regular frames, but this patch does not differenciate.

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Acked-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-agn.c

@@ -444,7 +444,7 @@ void iwl_hw_txq_free_tfd(struct iwl_priv *priv, struct iwl_tx_queue *txq)
 		pci_unmap_single(dev,
 				pci_unmap_addr(&txq->cmd[index]->meta, mapping),
 				pci_unmap_len(&txq->cmd[index]->meta, len),
-				PCI_DMA_TODEVICE);
+				PCI_DMA_BIDIRECTIONAL);
 
 	/* Unmap chunks, if any. */
 	for (i = 1; i < num_tbs; i++) {

drivers/net/wireless/iwlwifi/iwl-tx.c

@@ -819,7 +819,7 @@ int iwl_tx_skb(struct iwl_priv *priv, struct sk_buff *skb)
 	 * within command buffer array. */
 	txcmd_phys = pci_map_single(priv->pci_dev,
 				    out_cmd, sizeof(struct iwl_cmd),
-				    PCI_DMA_TODEVICE);
+				    PCI_DMA_BIDIRECTIONAL);
 	pci_unmap_addr_set(&out_cmd->meta, mapping, txcmd_phys);
 	pci_unmap_len_set(&out_cmd->meta, len, sizeof(struct iwl_cmd));
 	/* Add buffer containing Tx command and MAC(!) header to TFD's
@@ -968,7 +968,7 @@ int iwl_enqueue_hcmd(struct iwl_priv *priv, struct iwl_host_cmd *cmd)
 			IWL_MAX_SCAN_SIZE : sizeof(struct iwl_cmd);
 
 	phys_addr = pci_map_single(priv->pci_dev, out_cmd,
-				   len, PCI_DMA_TODEVICE);
+				   len, PCI_DMA_BIDIRECTIONAL);
 	pci_unmap_addr_set(&out_cmd->meta, mapping, phys_addr);
 	pci_unmap_len_set(&out_cmd->meta, len, len);
 	phys_addr += offsetof(struct iwl_cmd, hdr);
@@ -1068,7 +1068,7 @@ static void iwl_hcmd_queue_reclaim(struct iwl_priv *priv, int txq_id,
 	pci_unmap_single(priv->pci_dev,
 		pci_unmap_addr(&txq->cmd[cmd_idx]->meta, mapping),
 		pci_unmap_len(&txq->cmd[cmd_idx]->meta, len),
-		PCI_DMA_TODEVICE);
+		PCI_DMA_BIDIRECTIONAL);
 
 	for (idx = iwl_queue_inc_wrap(idx, q->n_bd); q->read_ptr != idx;
 	     q->read_ptr = iwl_queue_inc_wrap(q->read_ptr, q->n_bd)) {