tree 4f0666a793ec60dbd4194755d076b5c7ae709807
parent 7dc45f25d39ea959fdc1d5f636e9fc6cbe7ac7e0
author Fenghua Yu <fenghua.yu@intel.com> 1235001273 -0800
committer John W. Linville <linville@tuxdriver.com> 1235764367 -0500

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>