[PATCH 0/4] Remove default DMA window before creating DDW

[Leonardo Bras <leobras.c@gmail.com>]

There are some devices that only allow 1 DMA window to exist at a time,
and in those cases, a DDW is never created to them, since the default DMA
window keeps using this resource.

LoPAR recommends this procedure:
1. Remove the default DMA window,
2. Query for which configs the DDW can be created,
3. Create a DDW.

Patch #1:
- After LoPAR level 2.8, there is an extension that can make
  ibm,query-pe-dma-windows to have 6 outputs instead of 5. This changes the
  order of the outputs, and that can cause some trouble. 
- query_ddw() was updated to check how many outputs the 
  ibm,query-pe-dma-windows is supposed to have, update the rtas_call() and
  deal correctly with the outputs in both cases.
- This patch looks somehow unrelated to the series, but it can avoid future
  problems on DDW creation.

Patch #2 implements a new rtas call to recover the default DMA window,
in case anything fails after it was removed, and a DDW couldn't be created.

Patch #3 moves the window-removing code from remove_ddw() to
remove_dma_window(), creating a way to delete any DMA window, so it can be
used to delete the default DMA window.

Patch #4 makes use of the remove_dma_window() from patch #3 to remove the
default DMA window before query_ddw() and the rtas call from patch #2
to recover it if something goes wrong.

All patches were tested into an LPAR with an Ethernet VF:
4005:01:00.0 Ethernet controller: Mellanox Technologies MT27700 Family
[ConnectX-4 Virtual Function]

Leonardo Bras (4):
  powerpc/pseries/iommu: Update call to ibm,query-pe-dma-windows
  powerpc/pseries/iommu: Implement ibm,reset-pe-dma-windows rtas call
  powerpc/pseries/iommu: Move window-removing part of remove_ddw into
    remove_dma_window
  powerpc/pseries/iommu: Remove default DMA window before creating DDW

 arch/powerpc/platforms/pseries/iommu.c | 163 +++++++++++++++++++------
 1 file changed, 127 insertions(+), 36 deletions(-)

-- 
2.25.4