linux-kernel - [PATCH] serial: imx: Revert "initialized DMA w/o HW flow enabled"

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 7 May 2015 22:24:39 +0200
From:	Sebastian Andrzej Siewior <sebastian@...akpoint.cc>
To:	gregkh@...uxfoundation.org
Cc:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	jiwang <jiada_wang@...tor.com>, jslaby@...e.cz,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
	anton_bondarenko@...tor.com, dirk.behme@...bosch.com,
	Nicolae Rosia <nicolae.rosia@...il.com>,
	Fabio Estevam <fabio.estevam@...escale.com>
Subject: [PATCH] serial: imx: Revert "initialized DMA w/o HW flow enabled"

From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>

This basically reverts commit 068500e08dc8 ("serial: imx: initialized
DMA w/o HW flow enabled") simply because it does not work as expected
without additional magic which I am not aware of. The DMA mode is only
used for non-console UARTs so the "standard" boot test won't notice this.

I tested it on various IMX6 (S and Q) boards and the default SDMA firmware
that is included in ROM does work properly. The SDMA interrupt counter does
not stop increment (which means the SDMA does not stop working or the ACK
is working) and I see a lot of 0x00 (sometimes other bytes) which are added
to the tty buffer which are not part of the data transfer.
Jiada claimed that there is a firmware which makes it work but failed to
provide me a link to the firmware. All he said was that it can not be
shipped as part of the kernel due to license issues. I've found a firmware
blob in the FSL-tree but this firmware causes only TTY-overflows an *no*
data is transmitted.

Currently I see no other way out.

Fixes: 068500e08dc8 ("serial: imx: initialized DMA w/o HW flow enabled")
Cc: Fabio Estevam <fabio.estevam@...escale.com>
Cc: Jiada Wang <jiada_wang@...tor.com>
Cc: nicolae.rosia@...il.com
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 drivers/tty/serial/imx.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 8aff0b4d8ddf..e686c75fa4dc 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -1113,11 +1113,6 @@ static int imx_startup(struct uart_port *port)
 
 	writel(temp & ~UCR4_DREN, sport->port.membase + UCR4);
 
-	/* Can we enable the DMA support? */
-	if (is_imx6q_uart(sport) && !uart_console(port) &&
-	    !sport->dma_is_inited)
-		imx_uart_dma_init(sport);
-
 	spin_lock_irqsave(&sport->port.lock, flags);
 	/* Reset fifo's and state machines */
 	i = 100;
@@ -1308,6 +1303,17 @@ imx_set_termios(struct uart_port *port, struct ktermios *termios,
 			} else {
 				ucr2 |= UCR2_CTSC;
 			}
+
+			/*
+			 * Can we enable the DMA support? Be aware that
+			 * at least IMX6 needs to load external SDMA firmware in
+			 * order work properly. The in-ROM firmware is not
+			 * wokring properly.
+			 */
+			if ((ucr2 & UCR2_CTSC) && is_imx6q_uart(sport) &&
+			    !uart_console(port) && !sport->dma_is_inited)
+				imx_uart_dma_init(sport);
+
 		} else {
 			termios->c_cflag &= ~CRTSCTS;
 		}
@@ -1424,6 +1430,8 @@ imx_set_termios(struct uart_port *port, struct ktermios *termios,
 	if (UART_ENABLE_MS(&sport->port, termios->c_cflag))
 		imx_enable_ms(&sport->port);
 
+	if (sport->dma_is_inited && !sport->dma_is_enabled)
+		imx_enable_dma(sport);
 	spin_unlock_irqrestore(&sport->port.lock, flags);
 }
 
-- 
2.1.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/