[PATCH 1/2 v2] gpio: omap: make gpio numbering deterministical by using of aliases

[Uwe Kleine-König]

Traditionally the n-th gpio device probed by the omap gpio driver got
the gpio number range [n*32 .. n*32+31].
When order of the devices probed by the driver changes (which can happen
already now when some devices have a pinctrl and so the first probe
attempt returns -ENODEV) the numbering changes.

To ensure a deterministical numbering use of_alias_get_id to determine
the base for a given device. If no respective alias exists fall back to
the traditional numbering.

For the unusual case where only a part of the gpio devices have a
matching alias some of them might fail to probe. But if none of them has
an alias or all, there is no conflict which should be good enough to
maintain backward compatibility.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig at pengutronix.de>
---
 drivers/gpio/gpio-omap.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
index b98ede78c9d8..4d91792e7266 100644
--- a/drivers/gpio/gpio-omap.c
+++ b/drivers/gpio/gpio-omap.c
@@ -1053,9 +1053,26 @@ static int omap_gpio_chip_init(struct gpio_bank *bank, struct irq_chip *irqc)
 			bank->chip.parent = &omap_mpuio_device.dev;
 		bank->chip.base = OMAP_MPUIO(0);
 	} else {
+		int gpio_alias_id __maybe_unused;
+
 		bank->chip.label = "gpio";
-		bank->chip.base = gpio;
+
+#if defined(CONFIG_OF_GPIO)
+		/*
+		 * Traditionally the base is given out in first-come-first-serve
+		 * order.  This might shuffle the numbering of gpios if the
+		 * probe order changes.  So make the base deterministical if the
+		 * device tree specifies alias ids.
+		 */
+		gpio_alias_id = of_alias_get_id(bank->chip.of_node, "gpio");
+		if (gpio_alias_id >= 0)
+			bank->chip.base = bank->width * gpio_alias_id;
+		else
+#endif
+			bank->chip.base = gpio;
 	}
+
+
 	bank->chip.ngpio = bank->width;
 
 	ret = gpiochip_add_data(&bank->chip, bank);
-- 
2.8.1