[U-Boot] [PATCH v2 1/2] gpio: Add GPIO driver framework for Marvell SoCs

[Simon Guinot]

Hi Ajay,

On Wed, Aug 03, 2011 at 10:10:00AM +0530, Ajay Bhargav wrote:
> ----- "Simon Guinot" <simon at sequanux.org> wrote:
> 
> > AFAIK, Orion and Kirkwood SoCs don't provide bitwise set/clear for
> > GPIO output/direction registers. Instead, a register must be read
> > first to leave other bits unchanged (see __set_direction in
> > kw_gpio.c).
> > 
> > Is it possible to handle Armada SoCs GPIOs in a same way ? maybe
> > using
> > the pin registers (gpxx in the Armada struct gpio_reg array) ?
> > 
> > If not, this code is not Marvell generic but rather specific for
> > Armada
> > SoCs and then maybe armada_gpio is a better name...
> > 
> > Regards,
> > 
> > Simon
> 
> Hi Simon,
> 
> Yes its possible to implement code that way, Armada SoC does have GPIO
> registers for set/clear. what about register naming?? I think they are
> different for Kirkwood and Orion.

I think that the register names could be OK. But here is a most
important problem: On Orion/Kirkwood SoCs, a single GPIO output register
is available (no set/clear variants as for Armada). I missed that point
at my first look. It is quite problematic because only two registers are
shared between the different Marvell SoCs: level and direction. In fact,
this registers are probably relevant on every machines providing GPIOs...

Maybe that having two common registers is not enough to add
Orion/Kirkwood support to the mvgpio driver ?

> 
> One more thing which can be done to make this code generic is to have
> some macros which can be defined by individual arch for specific registers
> which are going to be in use e.g.
> 
> #define GPIO_PIN_LEVEL_REG
> #define GPIO_DIR_REG
> #define GPIO_PIN_SET_REG
> #define GPIO_PIN_CLR_REG

Yes, but how to handle both a single GPI0 output register and some GPIO
{set,clear} output registers (in a nice way) ?

Regards,

Simon
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