[PATCH v3] usb: dwc3: Runtime get and put usb power_supply handle

[Kyle Tso <kyletso@google.com>]

It is possible that the usb power_supply is registered after the probe
of dwc3. In this case, trying to get the usb power_supply during the
probe will fail and there is no chance to try again. Also the usb
power_supply might be unregistered at anytime so that the handle of it
in dwc3 would become invalid. To fix this, get the handle right before
calling to power_supply functions and put it afterward.

dwc3_gadet_vbus_draw might be in interrupt context. Create a kthread
worker beforehand and use it to process the "might-sleep"
power_supply_put ASAP after the property set.

Fixes: 6f0764b5adea ("usb: dwc3: add a power supply for current control")
Cc: stable@vger.kernel.org
Signed-off-by: Kyle Tso <kyletso@google.com>
---
v2 -> v3:
- Only move power_supply_put to a work. Still call _get_by_name and
  _set_property in dwc3_gadget_vbus_draw.
- Create a kthread_worker to handle the work

v1 -> v2:
- move power_supply_put out of interrupt context

 drivers/usb/dwc3/core.c   | 29 ++++++++++++----------------
 drivers/usb/dwc3/core.h   |  6 ++++--
 drivers/usb/dwc3/gadget.c | 40 +++++++++++++++++++++++++++++++++++----
 3 files changed, 52 insertions(+), 23 deletions(-)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 734de2a8bd21..82c8376330d7 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -1631,8 +1631,6 @@ static void dwc3_get_properties(struct dwc3 *dwc)
 	u8			tx_thr_num_pkt_prd = 0;
 	u8			tx_max_burst_prd = 0;
 	u8			tx_fifo_resize_max_num;
-	const char		*usb_psy_name;
-	int			ret;
 
 	/* default to highest possible threshold */
 	lpm_nyet_threshold = 0xf;
@@ -1667,12 +1665,7 @@ static void dwc3_get_properties(struct dwc3 *dwc)
 
 	dwc->sys_wakeup = device_may_wakeup(dwc->sysdev);
 
-	ret = device_property_read_string(dev, "usb-psy-name", &usb_psy_name);
-	if (ret >= 0) {
-		dwc->usb_psy = power_supply_get_by_name(usb_psy_name);
-		if (!dwc->usb_psy)
-			dev_err(dev, "couldn't get usb power supply\n");
-	}
+	device_property_read_string(dev, "usb-psy-name", &dwc->usb_psy_name);
 
 	dwc->has_lpm_erratum = device_property_read_bool(dev,
 				"snps,has-lpm-erratum");
@@ -2132,19 +2125,24 @@ static int dwc3_probe(struct platform_device *pdev)
 
 	dwc3_get_software_properties(dwc);
 
+	dwc->worker = kthread_create_worker(0, "dwc3-worker");
+	if (IS_ERR(dwc->worker))
+		return PTR_ERR(dwc->worker);
+	sched_set_fifo(dwc->worker->task);
+
 	dwc->reset = devm_reset_control_array_get_optional_shared(dev);
 	if (IS_ERR(dwc->reset)) {
 		ret = PTR_ERR(dwc->reset);
-		goto err_put_psy;
+		goto err_destroy_worker;
 	}
 
 	ret = dwc3_get_clocks(dwc);
 	if (ret)
-		goto err_put_psy;
+		goto err_destroy_worker;
 
 	ret = reset_control_deassert(dwc->reset);
 	if (ret)
-		goto err_put_psy;
+		goto err_destroy_worker;
 
 	ret = dwc3_clk_enable(dwc);
 	if (ret)
@@ -2245,9 +2243,8 @@ static int dwc3_probe(struct platform_device *pdev)
 	dwc3_clk_disable(dwc);
 err_assert_reset:
 	reset_control_assert(dwc->reset);
-err_put_psy:
-	if (dwc->usb_psy)
-		power_supply_put(dwc->usb_psy);
+err_destroy_worker:
+	kthread_destroy_worker(dwc->worker);
 
 	return ret;
 }
@@ -2258,6 +2255,7 @@ static void dwc3_remove(struct platform_device *pdev)
 
 	pm_runtime_get_sync(&pdev->dev);
 
+	kthread_destroy_worker(dwc->worker);
 	dwc3_core_exit_mode(dwc);
 	dwc3_debugfs_exit(dwc);
 
@@ -2276,9 +2274,6 @@ static void dwc3_remove(struct platform_device *pdev)
 	pm_runtime_set_suspended(&pdev->dev);
 
 	dwc3_free_event_buffers(dwc);
-
-	if (dwc->usb_psy)
-		power_supply_put(dwc->usb_psy);
 }
 
 #ifdef CONFIG_PM
diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index 1e561fd8b86e..3fc58204db6e 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -993,6 +993,7 @@ struct dwc3_scratchpad_array {
 /**
  * struct dwc3 - representation of our controller
  * @drd_work: workqueue used for role swapping
+ * @worker: dedicated kthread worker
  * @ep0_trb: trb which is used for the ctrl_req
  * @bounce: address of bounce buffer
  * @setup_buf: used while precessing STD USB requests
@@ -1045,7 +1046,7 @@ struct dwc3_scratchpad_array {
  * @role_sw: usb_role_switch handle
  * @role_switch_default_mode: default operation mode of controller while
  *			usb role is USB_ROLE_NONE.
- * @usb_psy: pointer to power supply interface.
+ * @usb_psy_name: name of the usb power supply interface
  * @usb2_phy: pointer to USB2 PHY
  * @usb3_phy: pointer to USB3 PHY
  * @usb2_generic_phy: pointer to array of USB2 PHYs
@@ -1163,6 +1164,7 @@ struct dwc3_scratchpad_array {
  */
 struct dwc3 {
 	struct work_struct	drd_work;
+	struct kthread_worker	*worker;
 	struct dwc3_trb		*ep0_trb;
 	void			*bounce;
 	u8			*setup_buf;
@@ -1223,7 +1225,7 @@ struct dwc3 {
 	struct usb_role_switch	*role_sw;
 	enum usb_dr_mode	role_switch_default_mode;
 
-	struct power_supply	*usb_psy;
+	const char		*usb_psy_name;
 
 	u32			fladj;
 	u32			ref_clk_per;
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 89fc690fdf34..1ff583281eff 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -30,6 +30,11 @@
 #define DWC3_ALIGN_FRAME(d, n)	(((d)->frame_number + ((d)->interval * (n))) \
 					& ~((d)->interval - 1))
 
+struct dwc3_psy_put {
+	struct kthread_work work;
+	struct power_supply *psy;
+};
+
 /**
  * dwc3_gadget_set_test_mode - enables usb2 test modes
  * @dwc: pointer to our context structure
@@ -3047,22 +3052,49 @@ static void dwc3_gadget_set_ssp_rate(struct usb_gadget *g,
 	spin_unlock_irqrestore(&dwc->lock, flags);
 }
 
+static void dwc3_gadget_psy_put(struct kthread_work *work)
+{
+	struct dwc3_psy_put	*psy_put = container_of(work, struct dwc3_psy_put, work);
+
+	power_supply_put(psy_put->psy);
+	kfree(psy_put);
+}
+
 static int dwc3_gadget_vbus_draw(struct usb_gadget *g, unsigned int mA)
 {
-	struct dwc3		*dwc = gadget_to_dwc(g);
+	struct dwc3			*dwc = gadget_to_dwc(g);
+	struct power_supply		*usb_psy;
 	union power_supply_propval	val = {0};
+	struct dwc3_psy_put		*psy_put;
 	int				ret;
 
 	if (dwc->usb2_phy)
 		return usb_phy_set_power(dwc->usb2_phy, mA);
 
-	if (!dwc->usb_psy)
+	if (!dwc->usb_psy_name)
 		return -EOPNOTSUPP;
 
+	usb_psy = power_supply_get_by_name(dwc->usb_psy_name);
+	if (!usb_psy) {
+		dev_err(dwc->dev, "couldn't get usb power supply\n");
+		return -ENODEV;
+	}
+
 	val.intval = 1000 * mA;
-	ret = power_supply_set_property(dwc->usb_psy, POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT, &val);
+	ret = power_supply_set_property(usb_psy, POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT, &val);
+	if (ret < 0) {
+		dev_err(dwc->dev, "failed to set power supply property\n");
+		return ret;
+	}
 
-	return ret;
+	psy_put = kzalloc(sizeof(*psy_put), GFP_ATOMIC);
+	if (!psy_put)
+		return -ENOMEM;
+	kthread_init_work(&psy_put->work, dwc3_gadget_psy_put);
+	psy_put->psy = usb_psy;
+	kthread_queue_work(dwc->worker, &psy_put->work);
+
+	return 0;
 }
 
 /**
-- 
2.46.0.rc2.264.g509ed76dc8-goog