gpio: realtek-otto: switch to 32-bit I/O

By using 16-bit I/O on the GPIO peripheral, which is apparently not safe
on MIPS, the IMR can end up containing garbage. This then results in
interrupt triggers for lines that don't have an interrupt handler
associated. The irq_desc lookup fails, and the ISR will not be cleared,
keeping the CPU busy until reboot, or until another IMR operation
restores the correct value. This situation appears to happen very
rarely, for < 0.5% of IMR writes.

Instead of using 8-bit or 16-bit I/O operations on the 32-bit memory
mapped peripheral registers, switch to using 32-bit I/O only, operating
on the entire bank for all single bit line settings. For 2-bit line
settings, with 16-bit port values, stick to manual (un)packing.

This issue has been seen on RTL8382M (HPE 1920-16G), RTL8391M (Netgear
GS728TP v2), and RTL8393M (D-Link DGS-1210-52 F3, Zyxel GS1900-48).

Reported-by: Luiz Angelo Daros de Luca <luizluca@gmail.com> # DGS-1210-52
Reported-by: Birger Koblitz <mail@birger-koblitz.de> # GS728TP
Reported-by: Jan Hoffmann <jan@3e8.eu> # 1920-16G
Fixes: 0d82fb1127fb ("gpio: Add Realtek Otto GPIO support")
Signed-off-by: Sander Vanheule <sander@svanheule.net>
Cc: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

gpio: realtek-otto: Make the irqchip immutable

Since commit 6c846d026d49 ("gpio: Don't fiddle with irqchips marked as
immutable") a warning is issued for the realtek-otto driver:

gpio gpiochip0: (18003500.gpio): not an immutable chip, please consider fixing it!

Make the driver's irqchip immutable to fix this.

Signed-off-by: Sander Vanheule <sander@svanheule.net>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

gpio: realtek-otto: Add RTL931x support

The RTL931x SoC series has support for 32 GPIOs, although not all lines
may be broken out to a physical pad.

The GPIO bank's parent interrupt can be routed to either or both of the
SoC's CPU cores by the GIC. Line-by-line IRQ balancing is not possible
on these SoCs.

Signed-off-by: Sander Vanheule <sander@svanheule.net>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

gpio: realtek-otto: Add RTL930x support

The RTL930x SoC series has support for 24 GPIOs, with the port order
reversed compared to RTL838x and RTL839x. The RTL930x series also has
two CPUs (VPEs) and can distribute individual GPIO interrupts between
them.

Signed-off-by: Sander Vanheule <sander@svanheule.net>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

gpio: realtek-otto: Support per-cpu interrupts

On SoCs with multiple cores, it is possible that the GPIO interrupt
controller supports assigning specific pins to one or more cores.

IRQ balancing can be performed on a line-by-line basis if the parent
interrupt is routed to all available cores, which is the default upon
initialisation.

Signed-off-by: Sander Vanheule <sander@svanheule.net>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

gpio: realtek-otto: Support reversed port layouts

The GPIO port layout on the RTL930x SoC series is reversed compared to
the RTL838x and RTL839x SoC series. Add new port offset calculator
functions to ensure the correct order is used when reading port IRQ
data, and ensure bgpio uses the right byte ordering.

Signed-off-by: Sander Vanheule <sander@svanheule.net>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

gpio: realtek-otto: fix GPIO line IRQ offset

The irqchip uses one domain for all GPIO lines, so the line offset
should be determined w.r.t. the first line of the first port, not the
first line of the triggered port.

Fixes: 0d82fb1127fb ("gpio: Add Realtek Otto GPIO support")
Signed-off-by: Sander Vanheule <sander@svanheule.net>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

gpio: Bulk conversion to generic_handle_domain_irq()

Wherever possible, replace constructs that match either
generic_handle_irq(irq_find_mapping()) or
generic_handle_irq(irq_linear_revmap()) to a single call to
generic_handle_domain_irq().

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>

gpio: Add Realtek Otto GPIO support

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>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>