There are some devices in which a hypervisor may 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: Create defines for outputs of ibm,ddw-applicable, so it's easier to identify them. Patch #2: - 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 #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(). It also 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. --- Changes since v4: - Removed patches 5+ in order to deal with a feature at a time - Remove unnecessary parentesis in patch #4 - Changed patch #4 title from "Remove default DMA window before creating DDW" - Included David Dai tested-by - v4 link: http://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=190051&state=%2A&archive=both Changes since v3: - Introduces new patch #5, to prepare for an important change in #6 - struct iommu_table was not being updated, so include a way to do this in patch #6. - Improved patch #4 based in a suggestion from Alexey, to make code more easily understandable - v3 link: http://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=187348&state=%2A&archive=both Changes since v2: - Change the way ibm,ddw-extensions is accessed, using a proper function instead of doing this inline everytime it's used. - Remove previous patch #6, as it doesn't look like it would be useful. - Add new patch, for changing names from direct* to dma*, as indirect mapping can be used from now on. - Fix some typos, corrects some define usage. - v2 link: http://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=185433&state=%2A&archive=both Changes since v1: - Add defines for ibm,ddw-applicable and ibm,ddw-extensions outputs - Merge aux function query_ddw_out_sz() into query_ddw() - Merge reset_dma_window() patch (prev. #2) into remove default DMA window patch (#4). - Keep device_node *np name instead of using pdn in remove_*() - Rename 'device_node *pdn' into 'parent' in new functions - Rename dfl_win to default_win - Only remove the default DMA window if there is no window available in first query. - Check if default DMA window can be restored before removing it. - Fix 'unitialized use' (found by travis mpe:ci-test) - New patches #5 and #6 - v1 link: http://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=184420&state=%2A&archive=both Special thanks for Alexey Kardashevskiy, Brian King and Oliver O'Halloran for the feedback provided! Leonardo Bras (4): powerpc/pseries/iommu: Create defines for operations in ibm,ddw-applicable powerpc/pseries/iommu: Update call to ibm,query-pe-dma-windows powerpc/pseries/iommu: Move window-removing part of remove_ddw into remove_dma_window powerpc/pseries/iommu: Allow bigger 64bit window by removing default DMA window arch/powerpc/platforms/pseries/iommu.c | 242 ++++++++++++++++++++----- 1 file changed, 195 insertions(+), 47 deletions(-) -- 2.25.4
