[PATCH v2 2/2] gpio: realtek-otto: make bank_read/write overridable by endian property

[Rustam Adilov <adilov@disroot.org>]

In order to have a working gpio controller with SWAP_IO_SPACE,
the bank_read/bank_write functions and the gen_gc_flag used for
gpio_generic_chip_config must be able to be changed to their
respective counterparts.

To do that, introduce checks for the presence of endian property
under the device tree node and if so, override what has been
set by GPIO_PORTS_REVERSED quirk flag. This way, existing device
trees are kept working as they were originally.

Both big-endian and little-endian properties must be checked
because there are devices that have GPIO_PORTS_REVERSED flag
and the others that don't.

Signed-off-by: Rustam Adilov <adilov@disroot.org>
---
 drivers/gpio/gpio-realtek-otto.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/gpio/gpio-realtek-otto.c b/drivers/gpio/gpio-realtek-otto.c
index 491fde846d46..e079b5180760 100644
--- a/drivers/gpio/gpio-realtek-otto.c
+++ b/drivers/gpio/gpio-realtek-otto.c
@@ -405,6 +405,16 @@ static int realtek_gpio_probe(struct platform_device *pdev)
 		ctrl->line_imr_pos = realtek_gpio_line_imr_pos_swapped;
 	}
 
+	if (device_property_read_bool(dev, "little-endian")) {
+		gen_gc_flags = 0;
+		ctrl->bank_read = realtek_gpio_bank_read;
+		ctrl->bank_write = realtek_gpio_bank_write;
+	} else if (device_is_big_endian(dev)) {
+		gen_gc_flags = GPIO_GENERIC_BIG_ENDIAN_BYTE_ORDER;
+		ctrl->bank_read = realtek_gpio_bank_read_swapped;
+		ctrl->bank_write = realtek_gpio_bank_write_swapped;
+	}
+
 	config = (struct gpio_generic_chip_config) {
 		.dev = dev,
 		.sz = 4,
-- 
2.55.0