gpio: tegra186: Force one interrupt per bank

Newer chips support up to 8 interrupts per bank, which can be useful to
balance the load and decrease latency. However, it also required a very
complicated interrupt routing to be set up. To keep things simple for
now, ensure that a single interrupt per bank is enforced, even if all
possible interrupts are described in device tree.
Signed-off-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

drivers/gpio/gpio-tegra186.c

@@ -81,6 +81,8 @@ struct tegra_gpio {
 	unsigned int *irq;
 
 	const struct tegra_gpio_soc *soc;
+	unsigned int num_irqs_per_bank;
+	unsigned int num_banks;
 
 	void __iomem *secure;
 	void __iomem *base;
@@ -594,6 +596,28 @@ static void tegra186_gpio_init_route_mapping(struct tegra_gpio *gpio)
 	}
 }
 
+static unsigned int tegra186_gpio_irqs_per_bank(struct tegra_gpio *gpio)
+{
+	struct device *dev = gpio->gpio.parent;
+
+	if (gpio->num_irq > gpio->num_banks) {
+		if (gpio->num_irq % gpio->num_banks != 0)
+			goto error;
+	}
+
+	if (gpio->num_irq < gpio->num_banks)
+		goto error;
+
+	gpio->num_irqs_per_bank = gpio->num_irq / gpio->num_banks;
+
+	return 0;
+
+error:
+	dev_err(dev, "invalid number of interrupts (%u) for %u banks\n",
+		gpio->num_irq, gpio->num_banks);
+	return -EINVAL;
+}
+
 static int tegra186_gpio_probe(struct platform_device *pdev)
 {
 	unsigned int i, j, offset;
@@ -608,7 +632,17 @@ static int tegra186_gpio_probe(struct platform_device *pdev)
 		return -ENOMEM;
 
 	gpio->soc = device_get_match_data(&pdev->dev);
+	gpio->gpio.label = gpio->soc->name;
+	gpio->gpio.parent = &pdev->dev;
+
+	/* count the number of banks in the controller */
+	for (i = 0; i < gpio->soc->num_ports; i++)
+		if (gpio->soc->ports[i].bank > gpio->num_banks)
+			gpio->num_banks = gpio->soc->ports[i].bank;
+
+	gpio->num_banks++;
 
+	/* get register apertures */
 	gpio->secure = devm_platform_ioremap_resource_byname(pdev, "security");
 	if (IS_ERR(gpio->secure)) {
 		gpio->secure = devm_platform_ioremap_resource(pdev, 0);
@@ -629,6 +663,10 @@ static int tegra186_gpio_probe(struct platform_device *pdev)
 
 	gpio->num_irq = err;
 
+	err = tegra186_gpio_irqs_per_bank(gpio);
+	if (err < 0)
+		return err;
+
 	gpio->irq = devm_kcalloc(&pdev->dev, gpio->num_irq, sizeof(*gpio->irq),
 				 GFP_KERNEL);
 	if (!gpio->irq)
@@ -642,9 +680,6 @@ static int tegra186_gpio_probe(struct platform_device *pdev)
 		gpio->irq[i] = err;
 	}
 
-	gpio->gpio.label = gpio->soc->name;
-	gpio->gpio.parent = &pdev->dev;
-
 	gpio->gpio.request = gpiochip_generic_request;
 	gpio->gpio.free = gpiochip_generic_free;
 	gpio->gpio.get_direction = tegra186_gpio_get_direction;
@@ -708,7 +743,30 @@ static int tegra186_gpio_probe(struct platform_device *pdev)
 	irq->parent_handler = tegra186_gpio_irq;
 	irq->parent_handler_data = gpio;
 	irq->num_parents = gpio->num_irq;
-	irq->parents = gpio->irq;
+
+	/*
+	 * To simplify things, use a single interrupt per bank for now. Some
+	 * chips support up to 8 interrupts per bank, which can be useful to
+	 * distribute the load and decrease the processing latency for GPIOs
+	 * but it also requires a more complicated interrupt routing than we
+	 * currently program.
+	 */
+	if (gpio->num_irqs_per_bank > 1) {
+		irq->parents = devm_kcalloc(&pdev->dev, gpio->num_banks,
+					    sizeof(*irq->parents), GFP_KERNEL);
+		if (!irq->parents)
+			return -ENOMEM;
+
+		for (i = 0; i < gpio->num_banks; i++)
+			irq->parents[i] = gpio->irq[i * gpio->num_irqs_per_bank];
+
+		irq->num_parents = gpio->num_banks;
+	} else {
+		irq->num_parents = gpio->num_irq;
+		irq->parents = gpio->irq;
+	}
+
+	tegra186_gpio_init_route_mapping(gpio);
 
 	np = of_find_matching_node(NULL, tegra186_pmc_of_match);
 	if (np) {
@@ -719,8 +777,6 @@ static int tegra186_gpio_probe(struct platform_device *pdev)
 			return -EPROBE_DEFER;
 	}
 
-	tegra186_gpio_init_route_mapping(gpio);
-
 	irq->map = devm_kcalloc(&pdev->dev, gpio->gpio.ngpio,
 				sizeof(*irq->map), GFP_KERNEL);
 	if (!irq->map)