dmaengine: dma-axi-dmac: use DMA pool to manange DMA descriptor

For architectures like Microblaze or arm64 (where this IP is used),
DMA_DIRECT_REMAP is set which means that dma_alloc_coherent() might
remap (and hence vmalloc()) some memory. This became visible in a design
where dma_direct_use_pool() is not possible.

With the above, when calling dma_free_coherent(), vunmap() would be
called from softirq context and thus leading to a BUG().

To fix it, use a dma pool that is allocated in
.device_alloc_chan_resources() and allocate blocks from it. The key
point is that now dma_pool_free() is used in axi_dmac_free_desc() to
free the blocks and that just frees the blocks from the pool in the
sense they can be used again. In other words, no actual call to
dma_free_coherent() happens. That only happens when destroying the pool
in axi_dmac_free_chan_resources() which does not happen in any interrupt
context.

Fixes: 3f8fd25936ee ("dmaengine: axi-dmac: Allocate hardware descriptors")
Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260424-dma-dmac-handle-vunmap-v4-4-90f43412fdc0@analog.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

0 files changed, 0 insertions, 0 deletions