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

From: Felix Radensky <[email-masked]>
Date: Tue, 11 Aug 2009 18:12:12 +0300

Anton Vorontsov wrote:
> 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 &&?

No, that's obviously a typo. Bitwise & intended.

> 
> 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;

The reads are from 2 different registers, how do you propose to replace
them by a single read ?

I'll implement mpc8572_gpio_get(), suitable for both 8572 and 8536.

> 
>> -	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,
>