Hi Alan,

On 08/09/21 8:21 pm, Alan Stern wrote:

On Wed, Sep 08, 2021 at 03:23:10PM +0530, Kishon Vijay Abraham I wrote:

quoted

It has been observed with certain PCIe USB cards (like Inateck connected
to AM64 EVM or J7200 EVM) that as soon as the primary roothub is
registered, port status change is handled even before xHC is running
leading to cold plug USB devices not detected. For such cases, registering
both the root hubs along with the second HCD is required. Add support for
deferring roothub registration in usb_add_hcd(), so that both primary and
secondary roothubs are registered along with the second HCD.

CC: stable@vger.kernel.org # 5.4+
Signed-off-by: Kishon Vijay Abraham I <redacted>
Suggested-by: Mathias Nyman <redacted>
Tested-by: Chris Chiu <redacted>
---
 drivers/usb/core/hcd.c  | 30 ++++++++++++++++++++++++------
 include/linux/usb/hcd.h |  2 ++
 2 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 0f8b7c93310e..30bbf4ac4284 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c

@@ -2775,6 +2775,7 @@ int usb_add_hcd(struct usb_hcd *hcd,
 {
 	int retval;
 	struct usb_device *rhdev;
+	struct usb_hcd *shared_hcd;
 
 	if (!hcd->skip_phy_initialization && usb_hcd_is_primary_hcd(hcd)) {
 		hcd->phy_roothub = usb_phy_roothub_alloc(hcd->self.sysdev);

@@ -2935,13 +2936,26 @@ int usb_add_hcd(struct usb_hcd *hcd,
 		goto err_hcd_driver_start;
 	}
 
+	/* starting here, usbcore will pay attention to the shared HCD roothub */
+	shared_hcd = hcd->shared_hcd;
+	if (!usb_hcd_is_primary_hcd(hcd) && shared_hcd && HCD_DEFER_RH_REGISTER(shared_hcd)) {
+		retval = register_root_hub(shared_hcd);
+		if (retval != 0)
+			goto err_register_root_hub;
+
+		if (shared_hcd->uses_new_polling && HCD_POLL_RH(shared_hcd))
+			usb_hcd_poll_rh_status(shared_hcd);
+	}
+
 	/* starting here, usbcore will pay attention to this root hub */
-	retval = register_root_hub(hcd);
-	if (retval != 0)
-		goto err_register_root_hub;
+	if (!HCD_DEFER_RH_REGISTER(hcd)) {
+		retval = register_root_hub(hcd);
+		if (retval != 0)
+			goto err_register_root_hub;
 
-	if (hcd->uses_new_polling && HCD_POLL_RH(hcd))
-		usb_hcd_poll_rh_status(hcd);
+		if (hcd->uses_new_polling && HCD_POLL_RH(hcd))
+			usb_hcd_poll_rh_status(hcd);
+	}
 
 	return retval;
 

@@ -2985,6 +2999,7 @@ EXPORT_SYMBOL_GPL(usb_add_hcd);
 void usb_remove_hcd(struct usb_hcd *hcd)
 {
 	struct usb_device *rhdev = hcd->self.root_hub;
+	unsigned rh_registered;

This really should be a bool, not an unsigned.  (Relatively unimportant.)

quoted

 	dev_info(hcd->self.controller, "remove, state %x\n", hcd->state);
 

@@ -2995,6 +3010,8 @@ void usb_remove_hcd(struct usb_hcd *hcd)
 
 	dev_dbg(hcd->self.controller, "roothub graceful disconnect\n");
 	spin_lock_irq (&hcd_root_hub_lock);
+	if (hcd->rh_registered == 1)
+		rh_registered = 1;

Just say: rh_registered = hcd->rh_registered

quoted

 	hcd->rh_registered = 0;
 	spin_unlock_irq (&hcd_root_hub_lock);
 

@@ -3004,7 +3021,8 @@ void usb_remove_hcd(struct usb_hcd *hcd)
 	cancel_work_sync(&hcd->died_work);
 
 	mutex_lock(&usb_bus_idr_lock);
-	usb_disconnect(&rhdev);		/* Sets rhdev to NULL */
+	if (rh_registered == 1)

Just say: if (rh_registered)

quoted

+		usb_disconnect(&rhdev);		/* Sets rhdev to NULL */

Didn't the compiler warn about using a possibly uninitialized variable?

I didn't see any. Possibly the warning levels are not correctly set in my setup.
Will address your comment and send the patch.

Thank You,
Kishon

The overall logic looks okay, apart from this one point.

Alan Stern

quoted

 	mutex_unlock(&usb_bus_idr_lock);
 
 	/*

diff --git a/include/linux/usb/hcd.h b/include/linux/usb/hcd.h
index 548a028f2dab..2c1fc9212cf2 100644
--- a/include/linux/usb/hcd.h
+++ b/include/linux/usb/hcd.h

@@ -124,6 +124,7 @@ struct usb_hcd {
 #define HCD_FLAG_RH_RUNNING		5	/* root hub is running? */
 #define HCD_FLAG_DEAD			6	/* controller has died? */
 #define HCD_FLAG_INTF_AUTHORIZED	7	/* authorize interfaces? */
+#define HCD_FLAG_DEFER_RH_REGISTER	8	/* Defer roothub registration */
 
 	/* The flags can be tested using these macros; they are likely to
 	 * be slightly faster than test_bit().

@@ -134,6 +135,7 @@ struct usb_hcd {
 #define HCD_WAKEUP_PENDING(hcd)	((hcd)->flags & (1U << HCD_FLAG_WAKEUP_PENDING))
 #define HCD_RH_RUNNING(hcd)	((hcd)->flags & (1U << HCD_FLAG_RH_RUNNING))
 #define HCD_DEAD(hcd)		((hcd)->flags & (1U << HCD_FLAG_DEAD))
+#define HCD_DEFER_RH_REGISTER(hcd) ((hcd)->flags & (1U << HCD_FLAG_DEFER_RH_REGISTER))
 
 	/*
 	 * Specifies if interfaces are authorized by default

-- 
2.17.1