Some UARTs add enhanced functions with unused bit in 16550 standard, like UART_IER_UUE bit, it cause XScale detect wrong. Now detect UART_IER_UUE and UART_IER_RTOIE to reduce the annoying wrong result which cause UARTs don't work.
Serial controller: Device 4348:3253(CH352 PCI based Multi-I/O Controller) is a example. It use UART_IER_UUE as the LOWPOWER function, you can get the datasheet from below urls: http://wch-ic.com/download/list.asp?id=116 CH352DS1.PDF http://wch-ic.com/download/list.asp?id=117 CH352DS2.PDF. I choice UART_IER_RTOIE as another test bit, because choice it is harmless for current code, we will set UART_CAP_RTOIE if it is XScale port. Signed-off-by: Wang YanQing <udkni...@gmail.com> --- drivers/tty/serial/8250/8250.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/drivers/tty/serial/8250/8250.c b/drivers/tty/serial/8250/8250.c index 0efc815..2c1f9c9 100644 --- a/drivers/tty/serial/8250/8250.c +++ b/drivers/tty/serial/8250/8250.c @@ -841,6 +841,7 @@ static void autoconfig_16550a(struct uart_8250_port *up) { unsigned char status1, status2; unsigned int iersave; + unsigned int iertest; up->port.type = PORT_16550A; up->capabilities |= UART_CAP_FIFO; @@ -966,16 +967,25 @@ static void autoconfig_16550a(struct uart_8250_port *up) * We're going to explicitly set the UUE bit to 0 before * trying to write and read a 1 just to make sure it's not * already a 1 and maybe locked there before we even start start. + * + * 01/03/2013 + * Some UARTs add enhanced functions with unused bit in + * 16550 standard, like UART_IER_UUE bit, it cause XScale + * detect wrong. Now detect UART_IER_UUE and UART_IER_RTOIE + * to reduce the annoying wrong result which cause UART don't + * work. */ iersave = serial_in(up, UART_IER); - serial_out(up, UART_IER, iersave & ~UART_IER_UUE); - if (!(serial_in(up, UART_IER) & UART_IER_UUE)) { + iertest = UART_IER_UUE | UART_IER_RTOIE; + + serial_out(up, UART_IER, iersave & ~iertest); + if (!(serial_in(up, UART_IER) & iertest)) { /* * OK it's in a known zero state, try writing and reading * without disturbing the current state of the other bits. */ - serial_out(up, UART_IER, iersave | UART_IER_UUE); - if (serial_in(up, UART_IER) & UART_IER_UUE) { + serial_out(up, UART_IER, iersave | iertest); + if ((serial_in(up, UART_IER) & iertest) == iertest) { /* * It's an Xscale. * We'll leave the UART_IER_UUE bit set to 1 (enabled). -- 1.7.11.1.116.g8228a23 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
