at_hdmac uses __raw_writel for register writes. In the absence of a barrier, the CPU may reorder the register operations. Introduce a write memory barrier so that the CPU does not reorder the channel enable, thus the start of the transfer, without making sure that all the pre-required register fields are already written.
Fixes: dc78baa2b90b ("dmaengine: at_hdmac: new driver for the Atmel AHB DMA Controller") Reported-by: Peter Rosin peda@axentia.se Signed-off-by: Tudor Ambarus tudor.ambarus@microchip.com Cc: stable@vger.kernel.org Link: https://lore.kernel.org/lkml/13c6c9a2-6db5-c3bf-349b-4c127ad3496a@axentia.se... --- drivers/dma/at_hdmac.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c index 80eeb4fb88ef..968a5aba47cd 100644 --- a/drivers/dma/at_hdmac.c +++ b/drivers/dma/at_hdmac.c @@ -256,6 +256,8 @@ static void atc_dostart(struct at_dma_chan *atchan, struct at_desc *first) ATC_SPIP_BOUNDARY(first->boundary)); channel_writel(atchan, DPIP, ATC_DPIP_HOLE(first->dst_hole) | ATC_DPIP_BOUNDARY(first->boundary)); + /* Don't allow CPU to reorder channel enable. */ + wmb(); dma_writel(atdma, CHER, atchan->mask);
vdbg_dump_regs(atchan);