Subject: Re: [PATCH] powerpc/85xx: Workaround MPC8536 GPIO 1 errata.

From: Anton Vorontsov <[email-masked]>
Date: Tue, 11 Aug 2009 17:44:50 +0400

On Tue, Aug 11, 2009 at 12:04:18PM +0300, Felix Radensky wrote:
> On MPC8536 Rev 1.0 the status of GPIO pins configured
> as output cannot be determined by reading GPDAT register.
> Workaround by reading the status of input pins from GPDAT
> and the status of output pins from a shadow register.
> 
> Signed-off-by: Felix Radensky <[email-masked]>
> ---
>  arch/powerpc/sysdev/mpc8xxx_gpio.c |    6 +++++-
>  1 files changed, 5 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/powerpc/sysdev/mpc8xxx_gpio.c b/arch/powerpc/sysdev/mpc8xxx_gpio.c
> index 103eace..0b996f3 100644
> --- a/arch/powerpc/sysdev/mpc8xxx_gpio.c
> +++ b/arch/powerpc/sysdev/mpc8xxx_gpio.c
> @@ -56,9 +56,13 @@ static void mpc8xxx_gpio_save_regs(struct of_mm_gpio_chip *mm)
>  
>  static int mpc8xxx_gpio_get(struct gpio_chip *gc, unsigned int gpio)
>  {
> +	u32 val;
>  	struct of_mm_gpio_chip *mm = to_of_mm_gpio_chip(gc);
> +	struct mpc8xxx_gpio_chip *mpc8xxx_gc = to_mpc8xxx_gpio_chip(mm);
> +	
> +	val = in_be32(mm->regs + GPIO_DAT) && ~in_be32(mm->regs + GPIO_DIR);

Are you sure about &&?

Plus, this are two reads instead of just one. I think it'll be better
to implement mpc8536_gpio_get(), and then do

if (of_device_is_compatible(np, ... 8536-gpio-bank ...))
	gc->get = mpc8536_gpio_get;
else
	gc->get = mpc8xxx_gpio_get;

> -	return in_be32(mm->regs + GPIO_DAT) & mpc8xxx_gpio2mask(gpio);
> +	return (val | mpc8xxx_gc->data) & mpc8xxx_gpio2mask(gpio);
>  }
>  
>  static void mpc8xxx_gpio_set(struct gpio_chip *gc, unsigned int gpio, int val)

Thanks,

-- 
Anton Vorontsov
email: [email-masked]
irc://irc.freenode.net/bd2