Re: [PATCH] serial: efm32: Fix parity management in 'efm32_uart_console_get_options()'

[Uwe Kleine-König]

On Fri, Feb 10, 2017 at 10:06:40PM +0100, Christophe JAILLET wrote:
> UARTn_FRAME_PARITY_ODD is 0x0300
> UARTn_FRAME_PARITY_EVEN is 0x0200
> So if the UART is configured for EVEN parity, it would be reported as ODD.
> Fix it by testing if the 2 bits are set in the ODD case.
> 
> Signed-off-by: Christophe JAILLET <christophe.jail...@wanadoo.fr>
> ---
> Un-tested
> ---
>  drivers/tty/serial/efm32-uart.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/efm32-uart.c b/drivers/tty/serial/efm32-uart.c
> index ebd8569f9ad5..84034ef20c88 100644
> --- a/drivers/tty/serial/efm32-uart.c
> +++ b/drivers/tty/serial/efm32-uart.c
> @@ -572,9 +572,9 @@ static void efm32_uart_console_get_options(struct 
> efm32_uart_port *efm_port,
>                       16 * (4 + (clkdiv >> 6)));
>  
>       frame = efm32_uart_read32(efm_port, UARTn_FRAME);
> -     if (frame & UARTn_FRAME_PARITY_ODD)
> +     if ((frame & UARTn_FRAME_PARITY_ODD) == UARTn_FRAME_PARITY_ODD)
>               *parity = 'o';
> -     else if (frame & UARTn_FRAME_PARITY_EVEN)
> +     else if ((frame & UARTn_FRAME_PARITY_EVEN) == UARTn_FRAME_PARITY_EVEN)

There is really a bug, but the fix looks wrong (although it does the
right thing). The check for UARTn_FRAME_PARITY_EVEN should check both
bits, too.

The right change that works independent of the actual
values would be:

diff --git a/drivers/tty/serial/efm32-uart.c b/drivers/tty/serial/efm32-uart.c
index 195acc868763..00cdffbe4eda 100644
--- a/drivers/tty/serial/efm32-uart.c
+++ b/drivers/tty/serial/efm32-uart.c
@@ -27,6 +27,7 @@
 #define UARTn_FRAME            0x04
 #define UARTn_FRAME_DATABITS__MASK     0x000f
 #define UARTn_FRAME_DATABITS(n)                ((n) - 3)
+#define UARTn_FRAME_PARITY             0x0300
 #define UARTn_FRAME_PARITY_NONE                0x0000
 #define UARTn_FRAME_PARITY_EVEN                0x0200
 #define UARTn_FRAME_PARITY_ODD         0x0300
@@ -572,12 +573,16 @@ static void efm32_uart_console_get_options(struct 
efm32_uart_port *efm_port,
                        16 * (4 + (clkdiv >> 6)));
 
        frame = efm32_uart_read32(efm_port, UARTn_FRAME);
-       if (frame & UARTn_FRAME_PARITY_ODD)
+       switch (frame & UARTn_FRAME_PARITY) {
+       case UARTn_FRAME_PARITY_ODD:
                *parity = 'o';
-       else if (frame & UARTn_FRAME_PARITY_EVEN)
+               break;
+       case UARTn_FRAME_PARITY_EVEN:
                *parity = 'e';
-       else
+               break;
+       default:
                *parity = 'n';
+       }
 
        *bits = (frame & UARTn_FRAME_DATABITS__MASK) -
                        UARTn_FRAME_DATABITS(4) + 4;


I'd suggest to add

Fixes: 3afbd89c9639 ("serial/efm32: add new driver")

Best regards
Uwe

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Pengutronix e.K.                           | Uwe Kleine-König            |
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