From mboxrd@z Thu Jan  1 00:00:00 1970
From: alexander.stein@systec-electronic.com (Alexander Stein)
Date: Wed, 1 Dec 2010 11:59:59 +0100
Subject: [patch 1/2] imx51: fix gpiolib support
In-Reply-To: <87hbexu7mr.fsf@lechat.rtp-net.org>
References: <20101201083715.625363724@rtp-net.org>
	<20101201092529.GE32355@pengutronix.de>
	<87hbexu7mr.fsf@lechat.rtp-net.org>
Message-ID: <201012011200.25430.alexander.stein@systec-electronic.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Wednesday 01 December 2010, 11:09:32 Arnaud Patard wrote:
> > Maybe only read GDIR on mx51?  Isn't the direction saved by gpiolib
> > somewhere in RAM?  Is the same needed on other SoCs, too (see below for
> > my grouping)?  Technically it's not needed at all I think.
> > (Documentation/gpio.txt has: "However, note that not all platforms can
> > read the value of output pins; those that can't should always return
> > zero.".  I didn't check if the implementation conforms here though.)
> 
> yeah, I know that the gpiolib allows that and in this case, it's always
> returning 0 but while I was debugging an other problem, I wanted to read
> output value and it was not working. The manual was not explicitely
> saying it was not possible so I thought it was a bug and propose a
> fix. Hopefully, sending this patch allows me to get more feedback and
> tell me if I got something wrong and there's a better fix.
> 
> > I wonder if cpu_is_mx51 is the right macro to test, I'd prefer something
> > like imx_gpio_vX().  IMHO the gpio stuff needs a major overhaul getting
> > rid of most runtime checks.
> 
> I used cpu_is_mx51() because I only had tested/seen that on imx515. I
> wanted to avoid breaking other systems while trying to fix mine.
> As regards getting rid of runtime checks, maybe registering different
> gpiochip depending on the SoC would allow to check it a init time and no
> more check later.

I can conform, that reading from GPIO_DR on mx35 works too. Also checked with 
the description is this register. It seem to show exactly what we want, 
regarding GPIO_GDIR value. So even evaluating GPIO_DIR isn't needed at all.
My fix was to simply replace GPIO_PSR with GPIO_DR.

Best regards,
Alexander