[PATCH 4.16 27/43] serial: samsung: fix maxburst parameter for DMA transactions

Greg Kroah-Hartman
2018-06-14T14:08:43Z

From: Marek Szyprowski <m.szyprowski@samsung.com>

commit aa2f80e752c75e593b3820f42c416ed9458fa73e upstream.

The best granularity of residue that DMA engine can report is in the BURST
units, so the serial driver must use MAXBURST = 1 and DMA_SLAVE_BUSWIDTH_1_BYTE
if it relies on exact number of bytes transferred by DMA engine.

Fixes: 62c37eedb74c ("serial: samsung: add dma reqest/release functions")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/tty/serial/samsung.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)

--- a/drivers/tty/serial/samsung.c
+++ b/drivers/tty/serial/samsung.c
@@ -862,15 +862,12 @@ static int s3c24xx_serial_request_dma(st
dma->rx_conf.direction = DMA_DEV_TO_MEM;
dma->rx_conf.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
dma->rx_conf.src_addr = p->port.mapbase + S3C2410_URXH;
- dma->rx_conf.src_maxburst = 16;
+ dma->rx_conf.src_maxburst = 1;

dma->tx_conf.direction = DMA_MEM_TO_DEV;
dma->tx_conf.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
dma->tx_conf.dst_addr = p->port.mapbase + S3C2410_UTXH;
- if (dma_get_cache_alignment() >= 16)
- dma->tx_conf.dst_maxburst = 16;
- else
- dma->tx_conf.dst_maxburst = 1;
+ dma->tx_conf.dst_maxburst = 1;

dma->rx_chan = dma_request_chan(p->port.dev, "rx");