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>

1 files changed, 3 insertions, 3 deletions

diff --git a/drivers/net/wireless/iwlwifi/iwl-tx.c b/drivers/net/wireless/iwlwifi/iwl-tx.c
index ae04c2086f70..dff60fb70214 100644
--- a/drivers/net/wireless/iwlwifi/iwl-tx.c
+++ b/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)) {