[v5] powerpc: gpio driver for mpc8349/8572/8610 and compatible

[Trent Piepho]

On Tue, 23 Sep 2008, Peter Korsgaard wrote:
> +- compatible : "fsl,<CHIP>-gpio" followed by "fsl,mpc8349-gpio" for
> +  83xx, "fsl,mpc8572-gpio" for 85xx and "fsl,mpc8610-gpio" for 86xx.

Why have the three different compatible settings when the code doesn't do
anything different?

> +#define MPC8XXX_GPIO_PINS	32

8572 has eight GPIOs.

I wrote an MPC8572 GPIO driver back in March, and posted it internally at
Freescale on June 2nd.  But it was just ignored...  I wonder what your secret
is to get Kumar to apply your patches?  It's too bad this work keeps getting
duplicated.

My patch started out *very* much like yours, except it pre-dated the OF gpio
controller stuff and of_mm_gpiochip so it didn't use that.

But, I'm using the GPIOs to bit-bang a JTAG bus in the 20-30 MHz range.  The
obvious GPIO driver is *much* too slow for that.  I got less than 3 MHz, and
your driver looks like it might be slightly slower than my initial driver.

So I went to a lot of effort to speed it up and managed to increase GPIO
performance by nearly a factor of 10.  Trying to commit my driver at this
point is probably hopeless and I doubt anyone else cares about gpio speed. 
But at least the number of gpios for 8572 can be fixed.