From: Peter Hurley Date: Mon, 9 Mar 2015 18:05:01 +0000 (-0400) Subject: serial: 8250: Check UART_SCR is writable X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=f01a0bd8921b9d6668d41fae3198970e6318f532;p=linux-beck.git serial: 8250: Check UART_SCR is writable Au1x00/RT2800+ doesn't implement the 8250 scratch register (and this may be true of other h/w currently supported by the 8250 driver); read back the canary value written to the scratch register to enable the console h/w restart after resume from system suspend. Fixes: 4516d50aabedb ("serial: 8250: Use canary to restart console ...") Reported-by: Mason Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c index 0a8f11b69e68..3e7cf3711378 100644 --- a/drivers/tty/serial/8250/8250_core.c +++ b/drivers/tty/serial/8250/8250_core.c @@ -3585,7 +3585,8 @@ void serial8250_suspend_port(int line) port->type != PORT_8250) { unsigned char canary = 0xa5; serial_out(up, UART_SCR, canary); - up->canary = canary; + if (serial_in(up, UART_SCR) == canary) + up->canary = canary; } uart_suspend_port(&serial8250_reg, port);