From: Tudor Ambarus <tudor.ambarus@xxxxxxxxxxxxx>
commit 580ee84405c27d6ed419abe4d2b3de1968abdafd upstream.
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@xxxxxxxxxx>
Signed-off-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/lkml/13c6c9a2-6db5-c3bf-349b-4c127ad3496a@xxxxxxxxxx/
Acked-by: Nicolas Ferre <nicolas.ferre@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20221025090306.297886-1-tudor.ambarus@xxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20221025090306.297886-14-tudor.ambarus@xxxxxxxxxxxxx
Signed-off-by: Vinod Koul <vkoul@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/dma/at_hdmac.c | 2 ++
1 file changed, 2 insertions(+)
--- a/drivers/dma/at_hdmac.c
+++ b/drivers/dma/at_hdmac.c
@@ -246,6 +246,8 @@ static void atc_dostart(struct at_dma_ch
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);
