tree 19e4fddc2cefedec5b3711ec23651d595aabaf91
parent ccadee9b1e90dc6d3d97a20ac96cb1a82e0d5a1d
author Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com> 1405721114 +0200
committer Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com> 1419325983 +0200

dmaengine: rcar-dmac: Cache hardware descriptors memory

Unlike DMA transfers descriptors that are preallocated and cached,
memory used to store hardware descriptors is allocated and freed with
the DMA coherent allocation API for every transfer. Besides degrading
performances, this creates a CMA stress test that seems to cause issues.
Running dmatest with the noverify option produces

[   50.066539] alloc_contig_range test_pages_isolated(6b845, 6b846) failed
[   50.235180] alloc_contig_range test_pages_isolated(6b848, 6b84e) failed
[   52.964584] alloc_contig_range test_pages_isolated(6b847, 6b848) failed
[   54.127113] alloc_contig_range test_pages_isolated(6b843, 6b844) failed
[   56.270253] alloc_contig_range test_pages_isolated(6b84c, 6b850) failed

The root cause needs to be fixed, but in the meantime, as a workaround
and a performance improvement, cache hardware descriptors.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>