phy: Track power-on and init counts in uclass

On boards using the RK3399 SoC, the USB OHCI and EHCI controllers share
the same PHY device instance. While these controllers are being stopped
they both attempt to power-off and deinitialize it, but trying to
power-off the deinitialized PHY device results in a hang. This usually
happens just before booting an OS, and can be explicitly triggered by
running "usb start; usb stop" in the U-Boot shell.

Implement a uclass-wide counting mechanism for PHY initialization and
power state change requests, so that we don't power-off/deinitialize a
PHY instance until all of its users want it done. The Allwinner A10 USB
PHY driver does this counting in-driver, remove those parts in favour of
this in-uclass implementation.

The sandbox PHY operations test needs some changes since the uclass will
no longer call into the drivers for actions matching its tracked state
(e.g. powering-off a powered-off PHY). Update that test, and add a new
one which simulates multiple users of a single PHY.

The major complication here is that PHY handles aren't deduplicated per
instance, so the obvious idea of putting the counts in the PHY handles
don't immediately work. It seems possible to bind a child udevice per
PHY instance to the PHY provider and deduplicate the handles in each
child's uclass-private areas, like in the CLK framework. An alternative
approach could be to use those bound child udevices themselves as the
PHY handles. Instead, to avoid the architectural changes those would
require, this patch solves things by dynamically allocating a list of
structs (one per instance) in the provider's uclass-private area.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Peter Robinson <pbrobinson@gmail.com> - Rock960

2 files changed, 137 insertions, 9 deletions

diff --git a/drivers/phy/allwinner/phy-sun4i-usb.c b/drivers/phy/allwinner/phy-sun4i-usb.c
index ab2a5d1..86c589a 100644
--- a/drivers/phy/allwinner/phy-sun4i-usb.c
+++ b/drivers/phy/allwinner/phy-sun4i-usb.c
@@ -125,7 +125,6 @@ struct sun4i_usb_phy_info {
 
 struct sun4i_usb_phy_plat {
 	void __iomem *pmu;
-	int power_on_count;
 	int gpio_vbus;
 	int gpio_vbus_det;
 	int gpio_id_det;
@@ -225,10 +224,6 @@ static int sun4i_usb_phy_power_on(struct phy *phy)
 		initial_usb_scan_delay = 0;
 	}
 
-	usb_phy->power_on_count++;
-	if (usb_phy->power_on_count != 1)
-		return 0;
-
 	if (usb_phy->gpio_vbus >= 0)
 		gpio_set_value(usb_phy->gpio_vbus, SUNXI_GPIO_PULL_UP);
 
@@ -240,10 +235,6 @@ static int sun4i_usb_phy_power_off(struct phy *phy)
 	struct sun4i_usb_phy_data *data = dev_get_priv(phy->dev);
 	struct sun4i_usb_phy_plat *usb_phy = &data->usb_phy[phy->id];
 
-	usb_phy->power_on_count--;
-	if (usb_phy->power_on_count != 0)
-		return 0;
-
 	if (usb_phy->gpio_vbus >= 0)
 		gpio_set_value(usb_phy->gpio_vbus, SUNXI_GPIO_PULL_DISABLE);
 
diff --git a/drivers/phy/phy-uclass.c b/drivers/phy/phy-uclass.c
index 706e9fd..49e2ec2 100644
--- a/drivers/phy/phy-uclass.c
+++ b/drivers/phy/phy-uclass.c
@@ -11,12 +11,96 @@
 #include <dm/device_compat.h>
 #include <dm/devres.h>
 #include <generic-phy.h>
+#include <linux/list.h>
+
+/**
+ * struct phy_counts - Init and power-on counts of a single PHY port
+ *
+ * This structure is used to keep track of PHY initialization and power
+ * state change requests, so that we don't power off and deinitialize a
+ * PHY instance until all of its users want it done. Otherwise, multiple
+ * consumers using the same PHY port can cause problems (e.g. one might
+ * call power_off() after another's exit() and hang indefinitely).
+ *
+ * @id: The PHY ID within a PHY provider
+ * @power_on_count: Times generic_phy_power_on() was called for this ID
+ *                  without a matching generic_phy_power_off() afterwards
+ * @init_count: Times generic_phy_init() was called for this ID
+ *              without a matching generic_phy_exit() afterwards
+ * @list: Handle for a linked list of these structures corresponding to
+ *        ports of the same PHY provider
+ */
+struct phy_counts {
+	unsigned long id;
+	int power_on_count;
+	int init_count;
+	struct list_head list;
+};
 
 static inline struct phy_ops *phy_dev_ops(struct udevice *dev)
 {
 	return (struct phy_ops *)dev->driver->ops;
 }
 
+static struct phy_counts *phy_get_counts(struct phy *phy)
+{
+	struct list_head *uc_priv;
+	struct phy_counts *counts;
+
+	if (!generic_phy_valid(phy))
+		return NULL;
+
+	uc_priv = dev_get_uclass_priv(phy->dev);
+	list_for_each_entry(counts, uc_priv, list)
+		if (counts->id == phy->id)
+			return counts;
+
+	return NULL;
+}
+
+static int phy_alloc_counts(struct phy *phy)
+{
+	struct list_head *uc_priv;
+	struct phy_counts *counts;
+
+	if (!generic_phy_valid(phy))
+		return 0;
+	if (phy_get_counts(phy))
+		return 0;
+
+	uc_priv = dev_get_uclass_priv(phy->dev);
+	counts = kzalloc(sizeof(*counts), GFP_KERNEL);
+	if (!counts)
+		return -ENOMEM;
+
+	counts->id = phy->id;
+	counts->power_on_count = 0;
+	counts->init_count = 0;
+	list_add(&counts->list, uc_priv);
+
+	return 0;
+}
+
+static int phy_uclass_pre_probe(struct udevice *dev)
+{
+	struct list_head *uc_priv = dev_get_uclass_priv(dev);
+
+	INIT_LIST_HEAD(uc_priv);
+
+	return 0;
+}
+
+static int phy_uclass_pre_remove(struct udevice *dev)
+{
+	struct list_head *uc_priv = dev_get_uclass_priv(dev);
+	struct phy_counts *counts, *next;
+
+	list_for_each_entry_safe(counts, next, uc_priv, list)
+		kfree(counts);
+
+	return 0;
+}
+
 static int generic_phy_xlate_offs_flags(struct phy *phy,
 					struct ofnode_phandle_args *args)
 {
@@ -88,6 +172,12 @@ int generic_phy_get_by_index_nodev(ofnode node, int index, struct phy *phy)
 		goto err;
 	}
 
+	ret = phy_alloc_counts(phy);
+	if (ret) {
+		debug("phy_alloc_counts() failed: %d\n", ret);
+		goto err;
+	}
+
 	return 0;
 
 err:
@@ -118,6 +208,7 @@ int generic_phy_get_by_name(struct udevice *dev, const char *phy_name,
 
 int generic_phy_init(struct phy *phy)
 {
+	struct phy_counts *counts;
 	struct phy_ops const *ops;
 	int ret;
 
@@ -126,10 +217,19 @@ int generic_phy_init(struct phy *phy)
 	ops = phy_dev_ops(phy->dev);
 	if (!ops->init)
 		return 0;
+
+	counts = phy_get_counts(phy);
+	if (counts->init_count > 0) {
+		counts->init_count++;
+		return 0;
+	}
+
 	ret = ops->init(phy);
 	if (ret)
 		dev_err(phy->dev, "PHY: Failed to init %s: %d.\n",
 			phy->dev->name, ret);
+	else
+		counts->init_count = 1;
 
 	return ret;
 }
@@ -154,6 +254,7 @@ int generic_phy_reset(struct phy *phy)
 
 int generic_phy_exit(struct phy *phy)
 {
+	struct phy_counts *counts;
 	struct phy_ops const *ops;
 	int ret;
 
@@ -162,16 +263,28 @@ int generic_phy_exit(struct phy *phy)
 	ops = phy_dev_ops(phy->dev);
 	if (!ops->exit)
 		return 0;
+
+	counts = phy_get_counts(phy);
+	if (counts->init_count == 0)
+		return 0;
+	if (counts->init_count > 1) {
+		counts->init_count--;
+		return 0;
+	}
+
 	ret = ops->exit(phy);
 	if (ret)
 		dev_err(phy->dev, "PHY: Failed to exit %s: %d.\n",
 			phy->dev->name, ret);
+	else
+		counts->init_count = 0;
 
 	return ret;
 }
 
 int generic_phy_power_on(struct phy *phy)
 {
+	struct phy_counts *counts;
 	struct phy_ops const *ops;
 	int ret;
 
@@ -180,16 +293,26 @@ int generic_phy_power_on(struct phy *phy)
 	ops = phy_dev_ops(phy->dev);
 	if (!ops->power_on)
 		return 0;
+
+	counts = phy_get_counts(phy);
+	if (counts->power_on_count > 0) {
+		counts->power_on_count++;
+		return 0;
+	}
+
 	ret = ops->power_on(phy);
 	if (ret)
 		dev_err(phy->dev, "PHY: Failed to power on %s: %d.\n",
 			phy->dev->name, ret);
+	else
+		counts->power_on_count = 1;
 
 	return ret;
 }
 
 int generic_phy_power_off(struct phy *phy)
 {
+	struct phy_counts *counts;
 	struct phy_ops const *ops;
 	int ret;
 
@@ -198,10 +321,21 @@ int generic_phy_power_off(struct phy *phy)
 	ops = phy_dev_ops(phy->dev);
 	if (!ops->power_off)
 		return 0;
+
+	counts = phy_get_counts(phy);
+	if (counts->power_on_count == 0)
+		return 0;
+	if (counts->power_on_count > 1) {
+		counts->power_on_count--;
+		return 0;
+	}
+
 	ret = ops->power_off(phy);
 	if (ret)
 		dev_err(phy->dev, "PHY: Failed to power off %s: %d.\n",
 			phy->dev->name, ret);
+	else
+		counts->power_on_count = 0;
 
 	return ret;
 }
@@ -316,4 +450,7 @@ int generic_phy_power_off_bulk(struct phy_bulk *bulk)
 UCLASS_DRIVER(phy) = {
 	.id		= UCLASS_PHY,
 	.name		= "phy",
+	.pre_probe	= phy_uclass_pre_probe,
+	.pre_remove	= phy_uclass_pre_remove,
+	.per_device_auto = sizeof(struct list_head),
 };