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authorWerner Zeh <werner.zeh@siemens.com>2017-05-17 10:13:24 +0200
committerWerner Zeh <werner.zeh@siemens.com>2017-05-18 13:09:17 +0200
commit43314ffae53b813c6a0d6e34723921316cf46f45 (patch)
treeaccfd1e7e84330d347f91b10ec8253ec9fc21f0c /src/drivers
parente87564ffe7d0636699467b776a24adffb2f11cca (diff)
downloadcoreboot-43314ffae53b813c6a0d6e34723921316cf46f45.tar.xz
uart: Fix bug in {uart8250, uart8250_mem, ns16550}_rx_byte functions
We have several different UART implementations of which three support a timeout when receiving characters. In all of these three implementations there is a bug where when the timeout is hit the last received character will be returned instead of the needed 0. The problem is that the timeout variable i is decremented after it has been checked in the while-loop. That leads to the fact that when the while-loop is aborted due to a timeout i will contain 0xffffffff and not 0. Thus in turn will fool the following if-statement leading to wrong return value to the caller in this case. Therefore the caller will see a received character event if there is none. Change-Id: I23ff531a1e729e816764f1a071484c924dcb0f85 Signed-off-by: Werner Zeh <werner.zeh@siemens.com> Reviewed-on: https://review.coreboot.org/19731 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Diffstat (limited to 'src/drivers')
-rw-r--r--src/drivers/uart/uart8250io.c3
-rw-r--r--src/drivers/uart/uart8250mem.c4
2 files changed, 5 insertions, 2 deletions
diff --git a/src/drivers/uart/uart8250io.c b/src/drivers/uart/uart8250io.c
index ac3315a421..4cc7fe3e0b 100644
--- a/src/drivers/uart/uart8250io.c
+++ b/src/drivers/uart/uart8250io.c
@@ -62,7 +62,8 @@ static int uart8250_can_rx_byte(unsigned base_port)
static unsigned char uart8250_rx_byte(unsigned base_port)
{
unsigned long int i = SINGLE_CHAR_TIMEOUT;
- while (i-- && !uart8250_can_rx_byte(base_port));
+ while (i && !uart8250_can_rx_byte(base_port))
+ i--;
if (i)
return inb(base_port + UART8250_RBR);
diff --git a/src/drivers/uart/uart8250mem.c b/src/drivers/uart/uart8250mem.c
index 4e53a92a46..a142cb111a 100644
--- a/src/drivers/uart/uart8250mem.c
+++ b/src/drivers/uart/uart8250mem.c
@@ -82,8 +82,10 @@ static int uart8250_mem_can_rx_byte(void *base)
static unsigned char uart8250_mem_rx_byte(void *base)
{
unsigned long int i = SINGLE_CHAR_TIMEOUT;
- while (i-- && !uart8250_mem_can_rx_byte(base))
+ while (i && !uart8250_mem_can_rx_byte(base)) {
udelay(1);
+ i--;
+ }
if (i)
return uart8250_read(base, UART8250_RBR);
else