linux-kernel - Re: Serial port initialization broken on Armada 370/XP due to "serial: 8250_dw: Don't use UPF_FIXED

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Message-ID: <20130228123421.GC5688@xps8300>
Date:	Thu, 28 Feb 2013 14:34:21 +0200
From:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:	Gregory CLEMENT <gregory.clement@...e-electrons.com>
Cc:	Jamie Iles <jamie@...ieiles.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jason Cooper <jason@...edaemon.net>,
	Andrew Lunn <andrew@...n.ch>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-serial@...r.kernel.org
Subject: Re: Serial port initialization broken on Armada 370/XP due to
 "serial: 8250_dw: Don't use UPF_FIXED_TYPE"

Hi,

On Thu, Feb 28, 2013 at 12:42:06PM +0100, Gregory CLEMENT wrote:
> >> Would you agree with this kind of patch to fix the issue?
> >>
> >> diff --git a/drivers/tty/serial/8250/8250.c b/drivers/tty/serial/8250/8250.c
> >> index e2ac25a..0b284c6 100644
> >> --- a/drivers/tty/serial/8250/8250.c
> >> +++ b/drivers/tty/serial/8250/8250.c
> >> @@ -1119,7 +1119,7 @@ static void autoconfig(struct uart_8250_port *up, unsigned int probeflags)
> >>         serial_out(up, UART_LCR, 0);
> >>
> >>         serial_out(up, UART_FCR, UART_FCR_ENABLE_FIFO);
> >> -       scratch = serial_in(up, UART_IIR) >> 6;
> >> +       scratch = (serial_in(up, UART_IIR) & 0xFF) >> 6;
> >>
> >>         switch (scratch) {
> >>         case 0:
> > 
> > Instead, can you test if it's enough for you to set the reg-io-width
> > to 1 instead of 4:
> 
> Yes indeed it worked and it seems to be the correct description of my
> hardware. So I will fix the dtsi file.
> 
> However isn't buggy to use a function as it returned a char whereas
> it returns an int?

Yes, the driver should probable be cleaned.

It seems to be happening in quite a few places in 8250.c.
autoconfig_16550a() has pretty much identical code in it, where
UART_IIR is read to unsigned char and shifted without a mask.

Br,

-- 
heikki
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