On Mon, 2021-03-15 at 16:10 +0100, Linus Walleij wrote:

On Mon, Mar 15, 2021 at 9:26 AM Sander Vanheule
[off-list ref] wrote:

quoted

Realtek MIPS SoCs (platform name Otto) have GPIO controllers with
up to
64 GPIOs, divided over two banks. Each bank has a set of registers
for
32 GPIOs, with support for edge-triggered interrupts.

Each GPIO bank consists of four 8-bit GPIO ports (ABCD and EFGH).
Most
registers pack one bit per GPIO, except for the IMR register, which
packs two bits per GPIO (AB-CD).

Although the byte order is currently assumed to have port A..D at
offset
0x0..0x3, this has been observed to be reversed on other, Lexra-
based,
SoCs (e.g. RTL8196E/97D/97F).

Interrupt support is disabled for the fallback devicetree-
compatible
'realtek,otto-gpio'. This allows for quick support of GPIO banks in
which the byte order would be unknown. In this case, the port
ordering
in the IMR registers may not match the reversed order in the other
registers (DCBA, and BA-DC or DC-BA).

Signed-off-by: Sander Vanheule <sander@svanheule.net>

Overall this is a beautiful driver and it makes use of all the
generic
frameworks I can think of. I don't see any reason not to merge
it so:
Reviewed-by: Linus Walleij <redacted>

Thanks for the review and the kind comments!

The following is some notes and nitpicks, nothing blocking any
merge, more like discussion.

quoted

+enum realtek_gpio_flags {
+       GPIO_INTERRUPTS = BIT(0),
+};

I suppose this looks like this because more flags will be introduced
when you add more functionality to the driver. Otherwise it seems
like overkill so a bool would suffice.

I would add a comment /* TODO: this will be expanded */

That's correct, I would like this to be extendable. Like the commit
message noted, some other SoC appear to have port order D-C-B-A. The
current driver only supports the A-B-C-D port order, so a flag could be
added to differentiate between A-first and D-first.

Another flag that will be added in the future, is one to indicate that
the GPIO block has extra interrupt control registers, located after the
second GPIO bank.

For example, the rtl9300-series appears to have both the reversed port
order, and an extra "interrupt enable" register. This is not yet
implemented, since I don't currently have a device with this type of
SoC.

quoted

+static inline u32 realtek_gpio_imr_bits(unsigned int pin, u32
value)
+{
+       return ((value & 0x3) << 2*(pin % 16));
+}

I would explain a bit about this, obviouslt it is two bit per
line, but it took me some time to parse, so a comment
about the bit layout would be nice.

quoted

+       unsigned int offset = pin/16;

Here that number appears again.

I've updated the patch (and added your Reviewed-by tags) for a v2.
Hopefully this is now more obvious from the code and comments.

Best,
Sander

The use of GPIO_GENERIC and GPIO irqchip is flawless
and first class.

Thanks!
Linus Walleij