From: Tomoya MORINAGA <tomoya.rohm@gmail.com>
Date: Thu, 12 Apr 2012 01:47:50 +0000 (+0900)
Subject: pch_uart: Fix dma channel unallocated issue
X-Git-Tag: v3.2.17~143
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=493fe64b95d87298d19d5390f82d822ff37cc38d;p=karo-tx-linux.git

pch_uart: Fix dma channel unallocated issue

commit af6d17cdc8c89aeb3101f0d27cd32fc0592b40b2 upstream.

This driver anticipates pch_uart_verify_port() is not called
during installation.
However, actually pch_uart_verify_port() is called during
installation.
As a result, memory access violation occurs like below.

0. initial value: use_dma=0
1. starup()
    - dma channel is not allocated because use_dma=0
2. pch_uart_verify_port()
    - Set use_dma=1
3. UART processing acts DMA mode because use_dma=1
     - memory access violation occurs!

This patch fixes the issue.

Solution:
Whenever pch_uart_verify_port() is called and then
dma channel is not allocated, the channel should be allocated.

Signed-off-by: Tomoya MORINAGA <tomoya.rohm@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/drivers/tty/serial/pch_uart.c b/drivers/tty/serial/pch_uart.c
index da776a07173f..a4b192dc0e29 100644
--- a/drivers/tty/serial/pch_uart.c
+++ b/drivers/tty/serial/pch_uart.c
@@ -1356,9 +1356,11 @@ static int pch_uart_verify_port(struct uart_port *port,
 			__func__);
 		return -EOPNOTSUPP;
 #endif
-		priv->use_dma = 1;
 		priv->use_dma_flag = 1;
 		dev_info(priv->port.dev, "PCH UART : Use DMA Mode\n");
+		if (!priv->use_dma)
+			pch_request_dma(port);
+		priv->use_dma = 1;
 	}
 
 	return 0;