Re: [PATCH RFC 3/3] MIPS: AR7: ensure the port type's FCR value is used

[James Hogan <james.hogan@mips.com>]

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On Sun, Oct 29, 2017 at 04:27:21PM +0100, Jonas Gorski wrote:
> Since commit aef9a7bd9b67 ("serial/uart/8250: Add tunable RX interrupt
> trigger I/F of FIFO buffers"), the port's default FCR value isn't used
> in serial8250_do_set_termios anymore, but copied over once in
> serial8250_config_port and then modified as needed.
> 
> Unfortunately, serial8250_config_port will never be called if the port
> is shared between kernel and userspace, and the port's flag doesn't have
> UPF_BOOT_AUTOCONF, which would trigger a serial8250_config_port as well.
> 
> This causes garbled output from userspace:
> 
> [    5.220000] random: procd urandom read with 49 bits of entropy available
> ers
>    [kee
> 
> Fix this by forcing it to be configured on boot, resulting in the
> expected output:
> 
> [    5.250000] random: procd urandom read with 50 bits of entropy available
> Press the [f] key and hit [enter] to enter failsafe mode
> Press the [1], [2], [3] or [4] key and hit [enter] to select the debug level
> 
> Fixes: aef9a7bd9b67 ("serial/uart/8250: Add tunable RX interrupt trigger I/F of FIFO buffers")
> Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
> ---
> I'm not sure if this is just AR7's issue, or if this points to a general
> issue for UARTs used as kernel console and login console with the "fixed"
> commit.

Thanks. Given nobody seems to have objected, I've applied to my
mips-fixes branch, with stable tag for 3.17+.

Cheers
James

> 
>  arch/mips/ar7/platform.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/mips/ar7/platform.c b/arch/mips/ar7/platform.c
> index 4674f1efbe7a..e1675c25d5d4 100644
> --- a/arch/mips/ar7/platform.c
> +++ b/arch/mips/ar7/platform.c
> @@ -575,7 +575,7 @@ static int __init ar7_register_uarts(void)
>  	uart_port.type		= PORT_AR7;
>  	uart_port.uartclk	= clk_get_rate(bus_clk) / 2;
>  	uart_port.iotype	= UPIO_MEM32;
> -	uart_port.flags		= UPF_FIXED_TYPE;
> +	uart_port.flags		= UPF_FIXED_TYPE | UPF_BOOT_AUTOCONF;
>  	uart_port.regshift	= 2;
>  
>  	uart_port.line		= 0;
> -- 
> 2.13.2
> 
> 

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