patch "serial: samsung: fix maxburst parameter for DMA transactions" added to tty-next

patch "serial: samsung: fix maxburst parameter for DMA transactions" added to tty-next

[gregkh]

This is a note to let you know that I've just added the patch titled

    serial: samsung: fix maxburst parameter for DMA transactions

to my tty git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-next branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will also be merged in the next major kernel release
during the merge window.

If you have any questions about this process, please let me know.


>From aa2f80e752c75e593b3820f42c416ed9458fa73e Mon Sep 17 00:00:00 2001
From: Marek Szyprowski <m.szyprowski@samsung.com>
Date: Thu, 10 May 2018 08:41:13 +0200
Subject: serial: samsung: fix maxburst parameter for DMA transactions

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(-)

diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
index 3f2f8c118ce0..64e96926f1ad 100644
--- a/drivers/tty/serial/samsung.c
+++ b/drivers/tty/serial/samsung.c
@@ -862,15 +862,12 @@ static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p)
 	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");
 
-- 
2.17.0