[PATCH] gpio: omap: make gpio numbering deterministical by using of aliases

[Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>]

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 number 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@xxxxxxxxxxxxxx>
---
Hello,

if you're happy with this patch I can follow up and add the respective
aliases to the device trees.

Best regards
Uwe

 drivers/gpio/gpio-omap.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
index b98ede78c9d8..6814245a54aa 100644
--- a/drivers/gpio/gpio-omap.c
+++ b/drivers/gpio/gpio-omap.c
@@ -1034,6 +1034,7 @@ static int omap_gpio_chip_init(struct gpio_bank *bank, struct irq_chip *irqc)
 	static int gpio;
 	int irq_base = 0;
 	int ret;
+	int gpio_alias_id;
 
 	/*
 	 * REVISIT eventually switch from OMAP-specific gpio structs
@@ -1056,6 +1057,17 @@ static int omap_gpio_chip_init(struct gpio_bank *bank, struct irq_chip *irqc)
 		bank->chip.label = "gpio";
 		bank->chip.base = 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;
+
 	bank->chip.ngpio = bank->width;
 
 	ret = gpiochip_add_data(&bank->chip, bank);
-- 
2.8.1

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