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, 1 insertions, 1 deletions

diff --git a/drivers/net/wireless/iwlwifi/iwl-agn.c b/drivers/net/wireless/iwlwifi/iwl-agn.c
index bcb94a01f94a..b49f9f7a8a67 100644
--- a/drivers/net/wireless/iwlwifi/iwl-agn.c
+++ b/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++) {