[PATCH][SRU Zesty] drivers/tty: 8250: only call fintek_8250_probe when doing port I/O

[Colin Ian King]

On 30/05/17 17:35, dann frazier wrote:
> From: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> 
> BugLink: https://bugs.launchpad.net/bugs/1692548
> 
> Commit fa01e2ca9f53 ("serial: 8250: Integrate Fintek into 8250_base")
> modified the probing logic for PNP0501 devices, to remove a collision
> between the generic 16550A driver and the Fintek driver, which reused
> the same ACPI _HID.
> 
> The Fintek device probe is now incorporated into the common 8250 probe
> path, and gets called for all discovered 16550A compatible devices,
> including ones that are MMIO mapped rather than IO mapped. However,
> the Fintek driver assumes the port base is a I/O address, and proceeds
> to probe some arbitrary offsets above it.
> 
> This is generally a wrong thing to do, but on ARM systems (having no
> native port I/O), this may result in faulting accesses of completely
> unrelated MMIO regions in the PCI I/O space. Given that this is at
> serial probe time, this results in hard to diagnose crashes at boot.
> 
> So let's restrict the Fintek probe to devices that we know are using
> port I/O in the first place.
> 
> Fixes: fa01e2ca9f53 ("serial: 8250: Integrate Fintek into 8250_base")
> Suggested-by: Arnd Bergmann <arnd at arndb.de>
> Reviewed-by: Ricardo Ribalda <ricardo.ribalda at gmail.com>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> Cc: stable <stable at vger.kernel.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
> (cherry picked from commit 4c4fc90964b1cf205a67df566cc82ea1731bcb00)
> Signed-off-by: dann frazier <dann.frazier at canonical.com>
> ---
>  drivers/tty/serial/8250/8250_port.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
> index c13fec451d03..331bbe38e34b 100644
> --- a/drivers/tty/serial/8250/8250_port.c
> +++ b/drivers/tty/serial/8250/8250_port.c
> @@ -1322,7 +1322,7 @@ static void autoconfig(struct uart_8250_port *up)
>  	/*
>  	 * Check if the device is a Fintek F81216A
>  	 */
> -	if (port->type == PORT_16550A)
> +	if (port->type == PORT_16550A && port->iotype == UPIO_PORT)
>  		fintek_8250_probe(up);
>  
>  	if (up->capabilities != old_capabilities) {
> 

Upstream cherry pick, looks sensible to me.

Thanks Dann

Acked-by: Colin Ian King <colin.king at canonical.com>