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| author | Werner Zeh <werner.zeh@siemens.com> | 2017-05-17 10:13:24 +0200 |
|---|---|---|
| committer | Werner Zeh <werner.zeh@siemens.com> | 2017-05-18 13:09:17 +0200 |
| commit | 43314ffae53b813c6a0d6e34723921316cf46f45 (patch) | |
| tree | accfd1e7e84330d347f91b10ec8253ec9fc21f0c /src/drivers | |
| parent | e87564ffe7d0636699467b776a24adffb2f11cca (diff) | |
| download | coreboot-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.c | 3 | ||||
| -rw-r--r-- | src/drivers/uart/uart8250mem.c | 4 |
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 |