usb: typec: fusb302: Improve suspend/resume handling

Remove the code which avoids doing i2c-transfers while our parent
i2c-adapter may be suspended by busy-waiting for our resume handler
to be called.

Instead move the interrupt handling from a threaded interrupt handler
to a work-queue and install a non-threaded interrupt handler which
normally queues the new interrupt handling work directly.

When our suspend handler gets called we set a flag which makes the new
non-threaded interrupt handler skip queueing the work before our parent
i2c-adapter is ready, instead the new non-threaded handler will record an
interrupt has happened during suspend and then our resume handler will
queue the work (at which point our parent will be ready).

Note normally i2c drivers solve the problem of not being able to access
the i2c bus until the i2c-controller is resumed by simply disabling their
irq from the suspend handler and re-enabling it on resume.

That is not possible with the fusb302 since the irq is a wakeup source
(it must be a wakeup source so that we can do PD negotiation when a
charger gets plugged in while suspended).

Besides avoiding the ugly busy-wait, this also fixes the following errors
which were logged by the busy-wait code when woken from suspend by plugging
in a Type-C device:

fusb302: i2c: pm suspend, retry 1 / 10
fusb302: i2c: pm suspend, retry 2 / 10
etc.

This commit also changes the devm_request_irq to a regular request_irq
+ free_irq, so that the work can be properly stopped. While at it also
properly disable the wake setting on the irq and also properly stop the
delayed work for bcl handling.
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/typec/tcpm/fusb302.c

@@ -23,6 +23,7 @@
 #include <linux/sched/clock.h>
 #include <linux/seq_file.h>
 #include <linux/slab.h>
+#include <linux/spinlock.h>
 #include <linux/string.h>
 #include <linux/types.h>
 #include <linux/usb/typec.h>
@@ -78,6 +79,10 @@ struct fusb302_chip {
 
 	struct regulator *vbus;
 
+	spinlock_t irq_lock;
+	struct work_struct irq_work;
+	bool irq_suspended;
+	bool irq_while_suspended;
 	int gpio_int_n;
 	int gpio_int_n_irq;
 	struct extcon_dev *extcon;
@@ -85,9 +90,6 @@ struct fusb302_chip {
 	struct workqueue_struct *wq;
 	struct delayed_work bc_lvl_handler;
 
-	atomic_t pm_suspend;
-	atomic_t i2c_busy;
-
 	/* lock for sharing chip states */
 	struct mutex lock;
 
@@ -233,43 +235,15 @@ static void fusb302_debugfs_exit(const struct fusb302_chip *chip) { }
 
 #endif
 
-#define FUSB302_RESUME_RETRY 10
-#define FUSB302_RESUME_RETRY_SLEEP 50
-
-static bool fusb302_is_suspended(struct fusb302_chip *chip)
-{
-	int retry_cnt;
-
-	for (retry_cnt = 0; retry_cnt < FUSB302_RESUME_RETRY; retry_cnt++) {
-		if (atomic_read(&chip->pm_suspend)) {
-			dev_err(chip->dev, "i2c: pm suspend, retry %d/%d\n",
-				retry_cnt + 1, FUSB302_RESUME_RETRY);
-			msleep(FUSB302_RESUME_RETRY_SLEEP);
-		} else {
-			return false;
-		}
-	}
-
-	return true;
-}
-
 static int fusb302_i2c_write(struct fusb302_chip *chip,
 			     u8 address, u8 data)
 {
 	int ret = 0;
 
-	atomic_set(&chip->i2c_busy, 1);
-
-	if (fusb302_is_suspended(chip)) {
-		atomic_set(&chip->i2c_busy, 0);
-		return -ETIMEDOUT;
-	}
-
 	ret = i2c_smbus_write_byte_data(chip->i2c_client, address, data);
 	if (ret < 0)
 		fusb302_log(chip, "cannot write 0x%02x to 0x%02x, ret=%d",
 			    data, address, ret);
-	atomic_set(&chip->i2c_busy, 0);
 
 	return ret;
 }
@@ -281,19 +255,12 @@ static int fusb302_i2c_block_write(struct fusb302_chip *chip, u8 address,
 
 	if (length <= 0)
 		return ret;
-	atomic_set(&chip->i2c_busy, 1);
-
-	if (fusb302_is_suspended(chip)) {
-		atomic_set(&chip->i2c_busy, 0);
-		return -ETIMEDOUT;
-	}
 
 	ret = i2c_smbus_write_i2c_block_data(chip->i2c_client, address,
 					     length, data);
 	if (ret < 0)
 		fusb302_log(chip, "cannot block write 0x%02x, len=%d, ret=%d",
 			    address, length, ret);
-	atomic_set(&chip->i2c_busy, 0);
 
 	return ret;
 }
@@ -303,18 +270,10 @@ static int fusb302_i2c_read(struct fusb302_chip *chip,
 {
 	int ret = 0;
 
-	atomic_set(&chip->i2c_busy, 1);
-
-	if (fusb302_is_suspended(chip)) {
-		atomic_set(&chip->i2c_busy, 0);
-		return -ETIMEDOUT;
-	}
-
 	ret = i2c_smbus_read_byte_data(chip->i2c_client, address);
 	*data = (u8)ret;
 	if (ret < 0)
 		fusb302_log(chip, "cannot read %02x, ret=%d", address, ret);
-	atomic_set(&chip->i2c_busy, 0);
 
 	return ret;
 }
@@ -326,12 +285,6 @@ static int fusb302_i2c_block_read(struct fusb302_chip *chip, u8 address,
 
 	if (length <= 0)
 		return ret;
-	atomic_set(&chip->i2c_busy, 1);
-
-	if (fusb302_is_suspended(chip)) {
-		atomic_set(&chip->i2c_busy, 0);
-		return -ETIMEDOUT;
-	}
 
 	ret = i2c_smbus_read_i2c_block_data(chip->i2c_client, address,
 					    length, data);
@@ -347,8 +300,6 @@ static int fusb302_i2c_block_read(struct fusb302_chip *chip, u8 address,
 	}
 
 done:
-	atomic_set(&chip->i2c_busy, 0);
-
 	return ret;
 }
 
@@ -1485,6 +1436,25 @@ static int fusb302_pd_read_message(struct fusb302_chip *chip,
 static irqreturn_t fusb302_irq_intn(int irq, void *dev_id)
 {
 	struct fusb302_chip *chip = dev_id;
+	unsigned long flags;
+
+	/* Disable our level triggered IRQ until our irq_work has cleared it */
+	disable_irq_nosync(chip->gpio_int_n_irq);
+
+	spin_lock_irqsave(&chip->irq_lock, flags);
+	if (chip->irq_suspended)
+		chip->irq_while_suspended = true;
+	else
+		schedule_work(&chip->irq_work);
+	spin_unlock_irqrestore(&chip->irq_lock, flags);
+
+	return IRQ_HANDLED;
+}
+
+void fusb302_irq_work(struct work_struct *work)
+{
+	struct fusb302_chip *chip = container_of(work, struct fusb302_chip,
+						 irq_work);
 	int ret = 0;
 	u8 interrupt;
 	u8 interrupta;
@@ -1613,8 +1583,7 @@ static irqreturn_t fusb302_irq_intn(int irq, void *dev_id)
 	}
 done:
 	mutex_unlock(&chip->lock);
-
-	return IRQ_HANDLED;
+	enable_irq(chip->gpio_int_n_irq);
 }
 
 static int init_gpio(struct fusb302_chip *chip)
@@ -1730,6 +1699,8 @@ static int fusb302_probe(struct i2c_client *client,
 	if (!chip->wq)
 		return -ENOMEM;
 
+	spin_lock_init(&chip->irq_lock);
+	INIT_WORK(&chip->irq_work, fusb302_irq_work);
 	INIT_DELAYED_WORK(&chip->bc_lvl_handler, fusb302_bc_lvl_handler_work);
 	init_tcpc_dev(&chip->tcpc_dev);
 
@@ -1749,10 +1720,9 @@ static int fusb302_probe(struct i2c_client *client,
 		goto destroy_workqueue;
 	}
 
-	ret = devm_request_threaded_irq(chip->dev, chip->gpio_int_n_irq,
-					NULL, fusb302_irq_intn,
-					IRQF_ONESHOT | IRQF_TRIGGER_LOW,
-					"fsc_interrupt_int_n", chip);
+	ret = request_irq(chip->gpio_int_n_irq, fusb302_irq_intn,
+			  IRQF_ONESHOT | IRQF_TRIGGER_LOW,
+			  "fsc_interrupt_int_n", chip);
 	if (ret < 0) {
 		dev_err(dev, "cannot request IRQ for GPIO Int_N, ret=%d", ret);
 		goto tcpm_unregister_port;
@@ -1775,6 +1745,10 @@ static int fusb302_remove(struct i2c_client *client)
 {
 	struct fusb302_chip *chip = i2c_get_clientdata(client);
 
+	disable_irq_wake(chip->gpio_int_n_irq);
+	free_irq(chip->gpio_int_n_irq, chip);
+	cancel_work_sync(&chip->irq_work);
+	cancel_delayed_work_sync(&chip->bc_lvl_handler);
 	tcpm_unregister_port(chip->tcpm_port);
 	destroy_workqueue(chip->wq);
 	fusb302_debugfs_exit(chip);
@@ -1785,19 +1759,29 @@ static int fusb302_remove(struct i2c_client *client)
 static int fusb302_pm_suspend(struct device *dev)
 {
 	struct fusb302_chip *chip = dev->driver_data;
+	unsigned long flags;
 
-	if (atomic_read(&chip->i2c_busy))
-		return -EBUSY;
-	atomic_set(&chip->pm_suspend, 1);
+	spin_lock_irqsave(&chip->irq_lock, flags);
+	chip->irq_suspended = true;
+	spin_unlock_irqrestore(&chip->irq_lock, flags);
 
+	/* Make sure any pending irq_work is finished before the bus suspends */
+	flush_work(&chip->irq_work);
 	return 0;
 }
 
 static int fusb302_pm_resume(struct device *dev)
 {
 	struct fusb302_chip *chip = dev->driver_data;
+	unsigned long flags;
 
-	atomic_set(&chip->pm_suspend, 0);
+	spin_lock_irqsave(&chip->irq_lock, flags);
+	if (chip->irq_while_suspended) {
+		schedule_work(&chip->irq_work);
+		chip->irq_while_suspended = false;
+	}
+	chip->irq_suspended = false;
+	spin_unlock_irqrestore(&chip->irq_lock, flags);
 
 	return 0;
 }