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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/soc
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/soc')
-rw-r--r--src/soc/broadcom/cygnus/ns16550.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/src/soc/broadcom/cygnus/ns16550.c b/src/soc/broadcom/cygnus/ns16550.c
index 71a4cb08ef..aa9dd2d818 100644
--- a/src/soc/broadcom/cygnus/ns16550.c
+++ b/src/soc/broadcom/cygnus/ns16550.c
@@ -84,8 +84,10 @@ static int ns16550_tst_byte(void)
static unsigned char ns16550_rx_byte(void)
{
unsigned long int i = SINGLE_CHAR_TIMEOUT;
- while (i-- && !ns16550_tst_byte())
+ while (i && !ns16550_tst_byte()) {
udelay(1);
+ i--;
+ }
if (i)
return read32(&regs->rbr);
else