greybus: arche-platform: Export fn to allow timesync driver to change the state

With the addition of the timesync driver and looking at the hardware
interfaces we have, its clear we need to add a new arche-platform state.

This patch adds ARCHE_PLATFORM_STATE_TIME_SYNC to the arche-platform driver
to facilitate transition to the TIME_SYNC state if-and-only-if the
arche-platform driver is in the ACTIVE state.

This is mainly needed as wake/detect lines are shared between TIMESYNC
operation and basic control functionality of APBs. So during TIMESYNC
we want to make sure that the events on wake/detect lines are
ignored by the arche-platform APB reset logic.

This patch adds one exported function, which can be invoked from
timesync driver code, allowing, switching between
ARCHE_PLATFORM_STATE_TIME_SYNC <=> ARCHE_PLATFORM_STATE_ACTIVE states.

[ bryan.odonoghue@linaro.org: Added mutex, massaged commit text ]
Reviewed-by: Vaibhav Hiremath <vaibhav.hiremath@linaro.org>
Signed-off-by: Vaibhav Hiremath <vaibhav.hiremath@linaro.org>
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Suggested-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/arche-platform.c

@@ -55,13 +55,97 @@ struct arche_platform_drvdata {
 
 	enum svc_wakedetect_state wake_detect_state;
 	int wake_detect_irq;
-	spinlock_t wake_lock;	/* Protect wake_detect_state */
+	spinlock_t wake_lock;			/* Protect wake_detect_state */
+	struct mutex platform_state_mutex;	/* Protect state */
 	unsigned long wake_detect_start;
 	struct notifier_block pm_notifier;
 
 	struct device *dev;
 };
 
+/*
+ * arche_platform_change_state: Change the operational state
+ *
+ * This exported function allows external drivers to change the state
+ * of the arche-platform driver.
+ * Note that this function only supports transitions between two states
+ * with limited functionality.
+ *
+ *  - ARCHE_PLATFORM_STATE_TIME_SYNC:
+ *    Once set, allows timesync operations between SVC <=> AP and makes
+ *    sure that arche-platform driver ignores any subsequent events/pulses
+ *    from SVC over wake/detect.
+ *
+ *  - ARCHE_PLATFORM_STATE_ACTIVE:
+ *    Puts back driver to active state, where any pulse from SVC on wake/detect
+ *    line would trigger either cold/standby boot.
+ *    Note: Transition request from this function does not trigger cold/standby
+ *          boot. It just puts back driver book keeping variable back to ACTIVE
+ *          state and restores the interrupt.
+ *
+ * Returns -ENODEV if device not found, -EAGAIN if the driver cannot currently
+ * satisfy the requested state-transition or -EINVAL for all other
+ * state-transition requests.
+ */
+int arche_platform_change_state(enum arche_platform_state state)
+{
+	struct arche_platform_drvdata *arche_pdata;
+	struct platform_device *pdev;
+	struct device_node *np;
+	int ret = -EAGAIN;
+	unsigned long flags;
+
+	np = of_find_compatible_node(NULL, NULL, "google,arche-platform");
+	if (!np) {
+		pr_err("google,arche-platform device node not found\n");
+		return -ENODEV;
+	}
+
+	pdev = of_find_device_by_node(np);
+	if (!pdev) {
+		pr_err("arche-platform device not found\n");
+		return -ENODEV;
+	}
+
+	arche_pdata = platform_get_drvdata(pdev);
+
+	mutex_lock(&arche_pdata->platform_state_mutex);
+	spin_lock_irqsave(&arche_pdata->wake_lock, flags);
+	if (arche_pdata->wake_detect_state != WD_STATE_IDLE) {
+		dev_err(arche_pdata->dev,
+			"driver busy with wake/detect line ops\n");
+		goto  exit;
+	}
+
+	if (arche_pdata->state == state) {
+		ret = 0;
+		goto exit;
+	}
+
+	if (arche_pdata->state == ARCHE_PLATFORM_STATE_OFF ||
+	    arche_pdata->state == ARCHE_PLATFORM_STATE_STANDBY ||
+	    arche_pdata->state == ARCHE_PLATFORM_STATE_FW_FLASHING) {
+		dev_err(arche_pdata->dev, "busy, request to retry later\n");
+		goto exit;
+	}
+
+	if (state == ARCHE_PLATFORM_STATE_TIME_SYNC) {
+		disable_irq(arche_pdata->wake_detect_irq);
+		arche_pdata->state = ARCHE_PLATFORM_STATE_TIME_SYNC;
+	} else if (state == ARCHE_PLATFORM_STATE_ACTIVE) {
+		arche_pdata->state = ARCHE_PLATFORM_STATE_ACTIVE;
+		enable_irq(arche_pdata->wake_detect_irq);
+	} else {
+		dev_err(arche_pdata->dev, "invalid state transition request\n");
+	}
+exit:
+	spin_unlock_irqrestore(&arche_pdata->wake_lock, flags);
+	mutex_unlock(&arche_pdata->platform_state_mutex);
+	of_node_put(np);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(arche_platform_change_state);
+
 static inline void svc_reset_onoff(unsigned int gpio, bool onoff)
 {
 	gpio_set_value(gpio, onoff);
@@ -195,6 +279,9 @@ static irqreturn_t arche_platform_wd_irq(int irq, void *devid)
 	return IRQ_HANDLED;
 }
 
+/*
+ * Requires arche_pdata->platform_state_mutex to be held
+ */
 static int arche_platform_coldboot_seq(struct arche_platform_drvdata *arche_pdata)
 {
 	int ret;
@@ -226,6 +313,9 @@ static int arche_platform_coldboot_seq(struct arche_platform_drvdata *arche_pdat
 	return 0;
 }
 
+/*
+ * Requires arche_pdata->platform_state_mutex to be held
+ */
 static void arche_platform_fw_flashing_seq(struct arche_platform_drvdata *arche_pdata)
 {
 	if (arche_pdata->state == ARCHE_PLATFORM_STATE_FW_FLASHING)
@@ -246,6 +336,9 @@ static void arche_platform_fw_flashing_seq(struct arche_platform_drvdata *arche_
 
 }
 
+/*
+ * Requires arche_pdata->platform_state_mutex to be held
+ */
 static void arche_platform_poweroff_seq(struct arche_platform_drvdata *arche_pdata)
 {
 	unsigned long flags;
@@ -280,9 +373,11 @@ static ssize_t state_store(struct device *dev,
 	struct arche_platform_drvdata *arche_pdata = platform_get_drvdata(pdev);
 	int ret = 0;
 
+	mutex_lock(&arche_pdata->platform_state_mutex);
+
 	if (sysfs_streq(buf, "off")) {
 		if (arche_pdata->state == ARCHE_PLATFORM_STATE_OFF)
-			return count;
+			goto exit;
 
 		/*  If SVC goes down, bring down APB's as well */
 		device_for_each_child(arche_pdata->dev, NULL, apb_poweroff);
@@ -291,19 +386,19 @@ static ssize_t state_store(struct device *dev,
 
 	} else if (sysfs_streq(buf, "active")) {
 		if (arche_pdata->state == ARCHE_PLATFORM_STATE_ACTIVE)
-			return count;
+			goto exit;
 
 		ret = arche_platform_coldboot_seq(arche_pdata);
 
 		assert_wakedetect(arche_pdata);
 	} else if (sysfs_streq(buf, "standby")) {
 		if (arche_pdata->state == ARCHE_PLATFORM_STATE_STANDBY)
-			return count;
+			goto exit;
 
 		dev_warn(arche_pdata->dev, "standby state not supported\n");
 	} else if (sysfs_streq(buf, "fw_flashing")) {
 		if (arche_pdata->state == ARCHE_PLATFORM_STATE_FW_FLASHING)
-			return count;
+			goto exit;
 
 		/* First we want to make sure we power off everything
 		 * and then enter FW flashing state */
@@ -319,6 +414,8 @@ static ssize_t state_store(struct device *dev,
 		ret = -EINVAL;
 	}
 
+exit:
+	mutex_unlock(&arche_pdata->platform_state_mutex);
 	return ret ? ret : count;
 }
 
@@ -336,6 +433,8 @@ static ssize_t state_show(struct device *dev,
 		return sprintf(buf, "standby\n");
 	case ARCHE_PLATFORM_STATE_FW_FLASHING:
 		return sprintf(buf, "fw_flashing\n");
+	case ARCHE_PLATFORM_STATE_TIME_SYNC:
+		return sprintf(buf, "time_sync\n");
 	default:
 		return sprintf(buf, "unknown state\n");
 	}
@@ -349,11 +448,15 @@ static int arche_platform_pm_notifier(struct notifier_block *notifier,
 	struct arche_platform_drvdata *arche_pdata =
 		container_of(notifier, struct arche_platform_drvdata,
 			     pm_notifier);
+	int ret = NOTIFY_DONE;
 
+	mutex_lock(&arche_pdata->platform_state_mutex);
 	switch (pm_event) {
 	case PM_SUSPEND_PREPARE:
-		if (arche_pdata->state != ARCHE_PLATFORM_STATE_ACTIVE)
-			return NOTIFY_STOP;
+		if (arche_pdata->state != ARCHE_PLATFORM_STATE_ACTIVE) {
+			ret = NOTIFY_STOP;
+			break;
+		}
 		device_for_each_child(arche_pdata->dev, NULL, apb_poweroff);
 		arche_platform_poweroff_seq(arche_pdata);
 		break;
@@ -364,8 +467,9 @@ static int arche_platform_pm_notifier(struct notifier_block *notifier,
 	default:
 		break;
 	}
+	mutex_unlock(&arche_pdata->platform_state_mutex);
 
-	return NOTIFY_DONE;
+	return ret;
 }
 
 static int arche_platform_probe(struct platform_device *pdev)
@@ -468,6 +572,7 @@ static int arche_platform_probe(struct platform_device *pdev)
 	arche_pdata->dev = &pdev->dev;
 
 	spin_lock_init(&arche_pdata->wake_lock);
+	mutex_init(&arche_pdata->platform_state_mutex);
 	arche_pdata->wake_detect_irq =
 		gpio_to_irq(arche_pdata->wake_detect_gpio);
 
@@ -489,6 +594,7 @@ static int arche_platform_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	mutex_lock(&arche_pdata->platform_state_mutex);
 	ret = arche_platform_coldboot_seq(arche_pdata);
 	if (ret) {
 		dev_err(dev, "Failed to cold boot svc %d\n", ret);
@@ -505,6 +611,8 @@ static int arche_platform_probe(struct platform_device *pdev)
 
 	arche_pdata->pm_notifier.notifier_call = arche_platform_pm_notifier;
 	ret = register_pm_notifier(&arche_pdata->pm_notifier);
+	mutex_unlock(&arche_pdata->platform_state_mutex);
+
 	if (ret) {
 		dev_err(dev, "failed to register pm notifier %d\n", ret);
 		goto err_populate;
@@ -516,6 +624,7 @@ static int arche_platform_probe(struct platform_device *pdev)
 err_populate:
 	arche_platform_poweroff_seq(arche_pdata);
 err_coldboot:
+	mutex_unlock(&arche_pdata->platform_state_mutex);
 	device_remove_file(&pdev->dev, &dev_attr_state);
 	return ret;
 }

drivers/staging/greybus/arche_platform.h

@@ -15,8 +15,10 @@ enum arche_platform_state {
 	ARCHE_PLATFORM_STATE_ACTIVE,
 	ARCHE_PLATFORM_STATE_STANDBY,
 	ARCHE_PLATFORM_STATE_FW_FLASHING,
+	ARCHE_PLATFORM_STATE_TIME_SYNC,
 };
 
+int arche_platform_change_state(enum arche_platform_state state);
 
 int __init arche_apb_init(void);
 void __exit arche_apb_exit(void);