[PATCH 2/2] drivers/gpio: Port gpio driver to layerscape platform

On Tue, Nov 3, 2015 at 12:19 PM, Liu Gang [off-list ref] wrote:

Layerscape has the same ip block/controller as
GPIO on powerpc platform(MPC8XXX).

So use portable i/o accessors, as in_be32/out_be32
accessors are Power architecture specific whereas
ioread32/iowrite32 and ioread32be/iowrite32be are
available in other architectures.

Layerscape GPIO controller's registers may be big
or little endian, so the code needs to get the
endian property from DTB, then make additional
functions to fit right register read/write
operations.

Currently the code can support ls2080a GPIO with
little endian registers. And it can also work well
on other layerscape platform with big endian GPIO
registers.

Signed-off-by: Liu Gang <redacted>
Signed-off-by: Shaveta Leekha <redacted>

This doesn't seem good. You are starting to duplicate stuff
that is already available inside the gpio-generic.c driver.

Why can't this driver just select GPIO_GENERIC in
Kconfig and use the common code for handling
the endianness accessors?

bgpio_init() takes a flag
BGPIOF_BIG_ENDIAN_BYTE_ORDER
to make all accesses big endian, so using the
generic GPIO library would save you a lot of code.

Just look at other drivers for those selecting GPIO_GENERIC,
including <linux/basic_mmio_gpio.h> and calling bgpio_init().
You might want to keep some local custom BE code around
the IRQ parts.

But I would do two patches:
- One that switches MPC8xxx to using GENERIC_GPIO
- One that adds BE support using that infrastructure

It will result in a lot less code. I think.

Yours,
Linus Walleij