greybus: arche-apb-ctrl: Add APB control driver

It was messy to integrate both SVC, APB (and any other arche
platform specific control) into one single driver. Especially
due to cross-dependency.

AP first needs to bringup SVC, as SVC should enable clock to APB.
APB should come up before HUB, as due to some reason HUB wouldn't
enumerate APB's is APB comes up later.
And on top of that we should have clean picture of hardware description
in DT file.

So this patch introduces APB control driver. Mostly copied from original
arche-platform driver + fixed boot sequence.

Signed-off-by: Vaibhav Hiremath <vaibhav.hiremath@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

1 files changed, 400 insertions, 0 deletions

diff --git a/drivers/staging/greybus/arche-apb-ctrl.c b/drivers/staging/greybus/arche-apb-ctrl.c
new file mode 100644
index 000000000000..efc1e42f8c61
--- /dev/null
+++ b/drivers/staging/greybus/arche-apb-ctrl.c
@@ -0,0 +1,400 @@
+/*
+ * Arche Platform driver to control APB.
+ *
+ * Copyright 2014-2015 Google Inc.
+ * Copyright 2014-2015 Linaro Ltd.
+ *
+ * Released under the GPLv2 only.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/sched.h>
+#include <linux/pm.h>
+#include <linux/delay.h>
+#include <linux/platform_device.h>
+#include <linux/gpio.h>
+#include <linux/clk.h>
+#include <linux/of_platform.h>
+#include <linux/of_gpio.h>
+#include <linux/of_irq.h>
+#include <linux/spinlock.h>
+#include <linux/regulator/consumer.h>
+#include <linux/pinctrl/consumer.h>
+
+enum apb_state {
+	APB_STATE_OFF,
+	APB_STATE_ACTIVE,
+	APB_STATE_STANDBY,
+};
+
+struct arche_apb_ctrl_drvdata {
+	/* Control GPIO signals to and from AP <=> AP Bridges */
+	int wake_detect_gpio; /* bi-dir,maps to WAKE_MOD & WAKE_FRAME signals */
+	int resetn_gpio;
+	int boot_ret_gpio;
+	int pwroff_gpio;
+	int wake_in_gpio;
+	int wake_out_gpio;
+	int pwrdn_gpio;
+
+	unsigned int wake_detect_irq;
+	enum apb_state state;
+
+	struct regulator *vcore;
+	struct regulator *vio;
+
+	unsigned int clk_en_gpio;
+	struct clk *clk;
+
+	struct pinctrl *pinctrl;
+	struct pinctrl_state *pin_default;
+
+	/* To protect concurrent access of GPIO registers, need protection */
+	spinlock_t lock;
+};
+
+/*
+ * Note that these low level api's are active high
+ */
+static inline void assert_gpio(unsigned int gpio)
+{
+	gpio_set_value(gpio, 1);
+	msleep(500);
+}
+
+static inline void deassert_gpio(unsigned int gpio)
+{
+	gpio_set_value(gpio, 0);
+}
+
+static irqreturn_t apb_ctrl_wake_detect_irq(int irq, void *devid)
+{
+	struct arche_apb_ctrl_drvdata *apb = devid;
+	unsigned long flags;
+
+	/*
+	 * TODO:
+	 * Since currently SoC GPIOs are being used we are safe here
+	 * But ideally we should create a workqueue and process the control
+	 * signals, especially when we start using GPIOs over slow
+	 * buses like I2C.
+	 */
+	if (!gpio_is_valid(apb->wake_detect_gpio) &&
+			!gpio_is_valid(apb->resetn_gpio))
+		return IRQ_HANDLED; /* Should it be IRQ_NONE ?? */
+
+	spin_lock_irqsave(&apb->lock, flags);
+
+	if (apb->state != APB_STATE_ACTIVE) {
+		/* Bring bridge out of reset on this event */
+		gpio_set_value(apb->resetn_gpio, 1);
+		apb->state = APB_STATE_ACTIVE;
+	} else {
+		/*
+		 * Assert Wake_OUT signal to APB
+		 * It would resemble WakeDetect module's signal pass-through
+		 */
+		/*
+		 * We have to generate the pulse, so we may need to schedule
+		 * workqueue here.
+		 *
+		 * Also, since we are using both rising and falling edge for
+		 * interrupt trigger, we may not need workqueue. Just pass
+		 * through the value to bridge.
+		 * Just read GPIO value and pass it to the bridge
+		 */
+	}
+
+	spin_unlock_irqrestore(&apb->lock, flags);
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * Note: Please do not modify the below sequence, as it is as per the spec
+ */
+static int apb_ctrl_init_seq(struct platform_device *pdev,
+		struct arche_apb_ctrl_drvdata *apb)
+{
+	struct device *dev = &pdev->dev;
+	int ret;
+
+	/* On DB3 clock was not mandatory */
+	if (gpio_is_valid(apb->clk_en_gpio)) {
+		ret = devm_gpio_request(dev, apb->clk_en_gpio, "apb_clk_en");
+		if (ret)
+			dev_err(dev, "Failed requesting APB clock en gpio %d\n",
+					apb->clk_en_gpio);
+		ret = gpio_direction_output(apb->clk_en_gpio, 1);
+		if (ret)
+			dev_err(dev, "failed to set APB clock en gpio dir:%d\n", ret);
+	}
+	/* Hold APB in reset state */
+	ret = devm_gpio_request(dev, apb->resetn_gpio, "apb-reset");
+	if (ret) {
+		dev_err(dev, "Failed requesting reset gpio %d\n",
+				apb->resetn_gpio);
+		return ret;
+	}
+	ret = gpio_direction_output(apb->resetn_gpio, 0);
+	if (ret) {
+		dev_err(dev, "failed to set reset gpio dir:%d\n", ret);
+		return ret;
+	}
+
+	ret = devm_gpio_request(dev, apb->pwroff_gpio, "pwroff_n");
+	if (ret) {
+		dev_err(dev, "Failed requesting pwroff_n gpio %d\n",
+				apb->pwroff_gpio);
+		return ret;
+	}
+	ret = gpio_direction_input(apb->pwroff_gpio);
+	if (ret) {
+		dev_err(dev, "failed to set pwroff gpio dir:%d\n", ret);
+		return ret;
+	}
+
+	/* Enable power to APB */
+	if (apb->vcore) {
+		ret = regulator_enable(apb->vcore);
+		if (ret) {
+			dev_err(dev, "failed to enable core regulator\n");
+			return ret;
+		}
+	}
+	if (apb->vio) {
+		ret = regulator_enable(apb->vio);
+		if (ret) {
+			dev_err(dev, "failed to enable IO regulator\n");
+			return ret;
+		}
+	}
+
+	ret = devm_gpio_request_one(dev, apb->boot_ret_gpio,
+			GPIOF_OUT_INIT_LOW, "boot retention");
+	if (ret) {
+		dev_err(dev, "Failed requesting bootret gpio %d\n",
+				apb->boot_ret_gpio);
+		return ret;
+	}
+	gpio_set_value(apb->boot_ret_gpio, 0);
+	udelay(50);
+
+	ret = devm_gpio_request(dev, apb->wake_detect_gpio, "wake detect");
+	if (ret)
+		dev_err(dev, "Failed requesting wake_detect gpio %d\n",
+				apb->wake_detect_gpio);
+
+	return ret;
+}
+
+static int apb_ctrl_get_devtree_data(struct platform_device *pdev,
+		struct arche_apb_ctrl_drvdata *apb)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+
+	apb->wake_detect_gpio = of_get_named_gpio(np, "wake-detect-gpios", 0);
+	if (!gpio_is_valid(apb->wake_detect_gpio)) {
+		dev_err(dev, "failed to get wake detect gpio\n");
+		return apb->wake_detect_gpio;
+	}
+
+	apb->resetn_gpio = of_get_named_gpio(np, "reset-gpios", 0);
+	if (!gpio_is_valid(apb->resetn_gpio)) {
+		dev_err(dev, "failed to get reset gpio\n");
+		return apb->resetn_gpio;
+	}
+
+	apb->boot_ret_gpio = of_get_named_gpio(np, "boot-ret-gpios", 0);
+	if (!gpio_is_valid(apb->boot_ret_gpio)) {
+		dev_err(dev, "failed to get boot retention gpio\n");
+		return apb->boot_ret_gpio;
+	}
+
+	/* It's not mandatory to support power management interface */
+	apb->pwroff_gpio = of_get_named_gpio(np, "pwr-off-gpios", 0);
+	if (!gpio_is_valid(apb->pwroff_gpio)) {
+		dev_info(dev, "failed to get power off gpio\n");
+		return apb->pwroff_gpio;
+	}
+
+	/* Do not make clock mandatory as of now (for DB3) */
+	apb->clk_en_gpio = of_get_named_gpio(np, "clock-en-gpio", 0);
+	if (!gpio_is_valid(apb->clk_en_gpio))
+		dev_err(dev, "failed to get clock en gpio\n");
+
+	apb->pwrdn_gpio = of_get_named_gpio(np, "pwr-down-gpios", 0);
+	if (!gpio_is_valid(apb->pwrdn_gpio))
+		dev_info(dev, "failed to get power down gpio\n");
+
+	/* Regulators are optional, as we may have fixed supply coming in */
+	apb->vcore = devm_regulator_get(dev, "vcore");
+	if (IS_ERR_OR_NULL(apb->vcore)) {
+		dev_info(dev, "no core regulator found\n");
+		apb->vcore = NULL;
+	}
+
+	apb->vio = devm_regulator_get(dev, "vio");
+	if (IS_ERR_OR_NULL(apb->vio)) {
+		dev_info(dev, "no IO regulator found\n");
+		apb->vio = NULL;
+	}
+
+	apb->pinctrl = devm_pinctrl_get(&pdev->dev);
+	if (IS_ERR(apb->pinctrl)) {
+		dev_err(&pdev->dev, "could not get pinctrl handle\n");
+		return PTR_ERR(apb->pinctrl);
+	}
+	apb->pin_default = pinctrl_lookup_state(apb->pinctrl, "default");
+	if (IS_ERR(apb->pin_default)) {
+		dev_err(&pdev->dev, "could not get default pin state\n");
+		return PTR_ERR(apb->pin_default);
+	}
+
+	return 0;
+}
+
+static void apb_ctrl_cleanup(struct arche_apb_ctrl_drvdata *apb)
+{
+	unsigned long flags;
+
+	if (apb->vcore && regulator_is_enabled(apb->vcore) > 0)
+		regulator_disable(apb->vcore);
+
+	if (apb->vio && regulator_is_enabled(apb->vio) > 0)
+		regulator_disable(apb->vio);
+
+	spin_lock_irqsave(&apb->lock, flags);
+	/* As part of exit, put APB back in reset state */
+	if (gpio_is_valid(apb->resetn_gpio))
+		gpio_set_value(apb->resetn_gpio, 0);
+
+	apb->state = APB_STATE_OFF;
+	spin_unlock_irqrestore(&apb->lock, flags);
+
+	/* TODO: May have to send an event to SVC about this exit */
+}
+
+static int arche_apb_ctrl_probe(struct platform_device *pdev)
+{
+	int ret;
+	struct arche_apb_ctrl_drvdata *apb;
+	struct device *dev = &pdev->dev;
+
+	apb = devm_kzalloc(&pdev->dev, sizeof(*apb), GFP_KERNEL);
+	if (!apb)
+		return -ENOMEM;
+
+	ret = apb_ctrl_get_devtree_data(pdev, apb);
+	if (ret) {
+		dev_err(dev, "failed to get apb devicetree data %d\n", ret);
+		return ret;
+	}
+
+	ret = apb_ctrl_init_seq(pdev, apb);
+	if (ret) {
+		dev_err(dev, "failed to set init state of control signal %d\n",
+				ret);
+		goto exit;
+	}
+
+	spin_lock_init(&apb->lock);
+
+	apb->state = APB_STATE_OFF;
+	/*
+	 * Assert AP module detect signal by pulling wake_detect low
+	 */
+	assert_gpio(apb->wake_detect_gpio);
+
+	/*
+	 * In order to receive an interrupt, the GPIO must be set to input mode
+	 */
+	gpio_direction_input(apb->wake_detect_gpio);
+
+	ret = devm_request_irq(dev, gpio_to_irq(apb->wake_detect_gpio),
+			apb_ctrl_wake_detect_irq, IRQF_TRIGGER_FALLING,
+			"wake detect", apb);
+	if (ret) {
+		dev_err(dev, "failed to request wake detect IRQ\n");
+		goto exit;
+	}
+
+	platform_set_drvdata(pdev, apb);
+
+	dev_info(&pdev->dev, "Device registered successfully\n");
+	return 0;
+
+exit:
+	apb_ctrl_cleanup(apb);
+	return ret;
+}
+
+static int arche_apb_ctrl_remove(struct platform_device *pdev)
+{
+	struct arche_apb_ctrl_drvdata *apb = platform_get_drvdata(pdev);
+
+	if (apb)
+		apb_ctrl_cleanup(apb);
+
+	platform_set_drvdata(pdev, NULL);
+
+	return 0;
+}
+
+static int arche_apb_ctrl_suspend(struct device *dev)
+{
+	/*
+	 * If timing profile premits, we may shutdown bridge
+	 * completely
+	 *
+	 * TODO: sequence ??
+	 *
+	 * Also, need to make sure we meet precondition for unipro suspend
+	 * Precondition: Definition ???
+	 */
+	return 0;
+}
+
+static int arche_apb_ctrl_resume(struct device *dev)
+{
+	/*
+	 * Atleast for ES2 we have to meet the delay requirement between
+	 * unipro switch and AP bridge init, depending on whether bridge is in
+	 * OFF state or standby state.
+	 *
+	 * Based on whether bridge is in standby or OFF state we may have to
+	 * assert multiple signals. Please refer to WDM spec, for more info.
+	 *
+	 */
+	return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(arche_apb_ctrl_pm_ops,
+			arche_apb_ctrl_suspend,
+			arche_apb_ctrl_resume);
+
+static struct of_device_id arche_apb_ctrl_of_match[] = {
+	{ .compatible = "usbffff,2", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, arche_apb_ctrl_of_match);
+
+static struct platform_driver arche_apb_ctrl_device_driver = {
+	.probe		= arche_apb_ctrl_probe,
+	.remove		= arche_apb_ctrl_remove,
+	.driver		= {
+		.name	= "arche-apb-ctrl",
+		.pm	= &arche_apb_ctrl_pm_ops,
+		.of_match_table = of_match_ptr(arche_apb_ctrl_of_match),
+	}
+};
+
+module_platform_driver(arche_apb_ctrl_device_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Vaibhav Hiremath <vaibhav.hiremath@linaro.org>");
+MODULE_DESCRIPTION("Arche APB control Driver");