[PATCH v5 2/2] usb: misc: onboard_usb_dev: don't defer probing after the device is configured

[James Clark <jjc@jclark.com>]

onboard_usb_dev breaks the rule that a driver must not return
-EPROBE_DEFER from its probe after it has registered child devices (see
commit fbc35b45f9f6 ("Add documentation on meaning of -EPROBE_DEFER")).
Its USB device driver sets generic_subclass, so the generic probe runs
first and registers the device's interfaces. onboard_dev_usbdev_probe()
then returns -EPROBE_DEFER until the platform device for the onboard
device has probed. On the BeagleY-AI, this results in a probe loop,
which has broken booting since commit f918e3804498 ("arm64: enable
HAVE_SHARED_GPIOS for all ARM64 platforms").

Call the generic driver's operations from the driver itself instead of
relying on generic_subclass, so that the probe is deferred before the
device is configured. The device now stays unconfigured while the probe
is deferred, including when the platform device never probes. Before, it
was configured and unconfigured repeatedly until the platform device
probed.

Make onboard_dev_usbdev_match() not match a device when neither its
node nor its peer hub's node has a platform device, so that the generic
driver binds it instead. If the platform device goes away between match
and probe, return -ENODEV instead of -EINVAL, so that usb_probe_device()
falls back to the generic driver.

Fixes: 8bc063641ceb ("usb: misc: Add onboard_usb_hub driver")
Suggested-by: Johan Hovold <johan@kernel.org>
Signed-off-by: James Clark <jjc@jclark.com>
---
Changes in v5:
- Stopped matching a device when neither its node nor its peer hub's
  node has a platform device, so that the generic driver binds it
  (Sashiko)
- Split the platform device lookup out of _find_onboard_dev() into
  onboard_dev_find_pdev(), and dropped the "failed to find device node
  for peer hub" error
- Commit message: explained the -ENODEV

Changes in v4:
- Switched to calling the generic driver's operations instead of
  setting generic_subclass, replacing pre_probe in the USB core

 drivers/usb/misc/onboard_usb_dev.c | 67 +++++++++++++++++++++---------
 1 file changed, 48 insertions(+), 19 deletions(-)

diff --git a/drivers/usb/misc/onboard_usb_dev.c b/drivers/usb/misc/onboard_usb_dev.c
index c60406240416..299e39b55e73 100644
--- a/drivers/usb/misc/onboard_usb_dev.c
+++ b/drivers/usb/misc/onboard_usb_dev.c
@@ -576,6 +576,25 @@ static struct platform_driver onboard_dev_driver = {
 #define VENDOR_ID_VIA		0x2109
 #define VENDOR_ID_XMOS		0x20B1
 
+static struct platform_device *onboard_dev_find_pdev(struct device *dev)
+{
+	struct platform_device *pdev;
+	struct device_node *np;
+
+	pdev = of_find_device_by_node(dev->of_node);
+	if (pdev)
+		return pdev;
+
+	np = of_parse_phandle(dev->of_node, "peer-hub", 0);
+	if (!np)
+		return NULL;
+
+	pdev = of_find_device_by_node(np);
+	of_node_put(np);
+
+	return pdev;
+}
+
 /*
  * Returns the onboard_dev platform device that is associated with the USB
  * device passed as parameter.
@@ -583,23 +602,11 @@ static struct platform_driver onboard_dev_driver = {
 static struct onboard_dev *_find_onboard_dev(struct device *dev)
 {
 	struct platform_device *pdev;
-	struct device_node *np;
 	struct onboard_dev *onboard_dev;
 
-	pdev = of_find_device_by_node(dev->of_node);
-	if (!pdev) {
-		np = of_parse_phandle(dev->of_node, "peer-hub", 0);
-		if (!np) {
-			dev_err(dev, "failed to find device node for peer hub\n");
-			return ERR_PTR(-EINVAL);
-		}
-
-		pdev = of_find_device_by_node(np);
-		of_node_put(np);
-
-		if (!pdev)
-			return ERR_PTR(-ENODEV);
-	}
+	pdev = onboard_dev_find_pdev(dev);
+	if (!pdev)
+		return ERR_PTR(-ENODEV);
 
 	onboard_dev = dev_get_drvdata(&pdev->dev);
 	put_device(&pdev->dev);
@@ -619,8 +626,22 @@ static struct onboard_dev *_find_onboard_dev(struct device *dev)
 
 static bool onboard_dev_usbdev_match(struct usb_device *udev)
 {
-	/* Onboard devices using this driver must have a device tree node */
-	return !!udev->dev.of_node;
+	struct platform_device *pdev;
+
+	/*
+	 * Onboard devices using this driver must have a device tree node with
+	 * a platform device, its own or its peer hub's. Leave any other device
+	 * to the generic driver.
+	 */
+	if (!udev->dev.of_node)
+		return false;
+
+	pdev = onboard_dev_find_pdev(&udev->dev);
+	if (!pdev)
+		return false;
+
+	put_device(&pdev->dev);
+	return true;
 }
 
 static int onboard_dev_usbdev_probe(struct usb_device *udev)
@@ -639,7 +660,11 @@ static int onboard_dev_usbdev_probe(struct usb_device *udev)
 	if (err)
 		return err;
 
-	return 0;
+	err = usb_generic_driver_probe(udev);
+	if (err)
+		onboard_dev_remove_usbdev(onboard_dev, udev);
+
+	return err;
 }
 
 static void onboard_dev_usbdev_disconnect(struct usb_device *udev)
@@ -647,6 +672,7 @@ static void onboard_dev_usbdev_disconnect(struct usb_device *udev)
 	struct onboard_dev *onboard_dev = dev_get_drvdata(&udev->dev);
 
 	onboard_dev_remove_usbdev(onboard_dev, udev);
+	usb_generic_driver_disconnect(udev);
 }
 
 static const struct usb_device_id onboard_dev_id_table[] = {
@@ -697,7 +723,10 @@ static struct usb_device_driver onboard_dev_usbdev_driver = {
 	.match = onboard_dev_usbdev_match,
 	.probe = onboard_dev_usbdev_probe,
 	.disconnect = onboard_dev_usbdev_disconnect,
-	.generic_subclass = 1,
+#ifdef CONFIG_PM
+	.suspend = usb_generic_driver_suspend,
+	.resume = usb_generic_driver_resume,
+#endif
 	.supports_autosuspend =	1,
 	.id_table = onboard_dev_id_table,
 };
-- 
2.56.0