[PATCH v2 0/3] Fix cold plugged USB device on certain PCIe USB cards

Cold plugged USB device was not detected on certain PCIe USB cards
(like Inateck card connected to AM64 EVM or connected to J7200 EVM).

Re-plugging the USB device always gets it enumerated.

This issue was discussed in
https://lore.kernel.org/r/772e4001-178e-4918-032c-6e625bdded24@ti.com
and
https://bugzilla.kernel.org/show_bug.cgi?id=214021

So the suggested solution is to register both root hubs along with the
second hcd for xhci.

RFC Patch series can be found at [1]
v1 Patch series can be found at [3]

Changes from RFC:
1) Mathias identified potential issues with the RFC patch [2] and suggested
   the solution to use HCD flags. This series implements it.

Changes from v1:
1) Fixed code comments pointed out by Alan Stern
2) Renamed the HCD flag variable to "HCD_FLAG_DEFER_RH_REGISTER" from
   "HCD_FLAG_DEFER_PRI_RH_REGISTER"

[1] -> https://lore.kernel.org/linux-usb/20210824105302.25382-1-kishon@ti.com/
[2] -> https://lore.kernel.org/linux-usb/06693934-28f2-d59e-b004-62cabd3f9e8e@linux.intel.com
[3] -> https://lore.kernel.org/r/20210825105132.10420-1-kishon@ti.com

Kishon Vijay Abraham I (3):
  usb: core: hcd: Modularize HCD stop configuration in usb_stop_hcd()
  usb: core: hcd: Add support for deferring roothub registration
  xhci: Set HCD flag to defer primary roothub registration

 drivers/usb/core/hcd.c  | 66 +++++++++++++++++++++++++++--------------
 drivers/usb/host/xhci.c |  1 +
 include/linux/usb/hcd.h |  2 ++
 3 files changed, 47 insertions(+), 22 deletions(-)

-- 
2.17.1

No functional change. Since configuration to stop HCD is invoked from
multiple places, group all of them in usb_stop_hcd().

Signed-off-by: Kishon Vijay Abraham I <redacted>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Chris Chiu <redacted>
---
 drivers/usb/core/hcd.c | 39 ++++++++++++++++++++++-----------------
 1 file changed, 22 insertions(+), 17 deletions(-)

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 0f8b7c93310e..00d35fe1fef0 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c

@@ -2760,6 +2760,26 @@ static void usb_put_invalidate_rhdev(struct usb_hcd *hcd)
 	usb_put_dev(rhdev);
 }
 
+/**
+ * usb_stop_hcd - Halt the HCD
+ * @hcd: the usb_hcd that has to be halted
+ *
+ * Stop the root-hub polling timer and invoke the HCD's ->stop callback.
+ */
+static void usb_stop_hcd(struct usb_hcd *hcd)
+{
+	hcd->rh_pollable = 0;
+	clear_bit(HCD_FLAG_POLL_RH, &hcd->flags);
+	del_timer_sync(&hcd->rh_timer);
+
+	hcd->driver->stop(hcd);
+	hcd->state = HC_STATE_HALT;
+
+	/* In case the HCD restarted the timer, stop it again. */
+	clear_bit(HCD_FLAG_POLL_RH, &hcd->flags);
+	del_timer_sync(&hcd->rh_timer);
+}
+
 /**
  * usb_add_hcd - finish generic HCD structure initialization and register
  * @hcd: the usb_hcd structure to initialize

@@ -2946,13 +2966,7 @@ int usb_add_hcd(struct usb_hcd *hcd,
 	return retval;
 
 err_register_root_hub:
-	hcd->rh_pollable = 0;
-	clear_bit(HCD_FLAG_POLL_RH, &hcd->flags);
-	del_timer_sync(&hcd->rh_timer);
-	hcd->driver->stop(hcd);
-	hcd->state = HC_STATE_HALT;
-	clear_bit(HCD_FLAG_POLL_RH, &hcd->flags);
-	del_timer_sync(&hcd->rh_timer);
+	usb_stop_hcd(hcd);
 err_hcd_driver_start:
 	if (usb_hcd_is_primary_hcd(hcd) && hcd->irq > 0)
 		free_irq(irqnum, hcd);

@@ -3022,16 +3036,7 @@ void usb_remove_hcd(struct usb_hcd *hcd)
 	 * interrupt occurs), but usb_hcd_poll_rh_status() won't invoke
 	 * the hub_status_data() callback.
 	 */
-	hcd->rh_pollable = 0;
-	clear_bit(HCD_FLAG_POLL_RH, &hcd->flags);
-	del_timer_sync(&hcd->rh_timer);
-
-	hcd->driver->stop(hcd);
-	hcd->state = HC_STATE_HALT;
-
-	/* In case the HCD restarted the timer, stop it again. */
-	clear_bit(HCD_FLAG_POLL_RH, &hcd->flags);
-	del_timer_sync(&hcd->rh_timer);
+	usb_stop_hcd(hcd);
 
 	if (usb_hcd_is_primary_hcd(hcd)) {
 		if (hcd->irq > 0)

-- 
2.17.1

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.

Signed-off-by: Kishon Vijay Abraham I <redacted>
Suggested-by: Mathias Nyman <redacted>
Tested-by: Chris Chiu <redacted>
---
 drivers/usb/core/hcd.c  | 27 ++++++++++++++++++++++-----
 include/linux/usb/hcd.h |  2 ++
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 00d35fe1fef0..64fdfc6692c2 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c

@@ -2795,6 +2795,7 @@ 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);

@@ -2955,18 +2956,34 @@ 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_shared_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;
 
 err_register_root_hub:
 	usb_stop_hcd(hcd);
+err_register_shared_root_hub:
+	if (!usb_hcd_is_primary_hcd(hcd) && shared_hcd && HCD_DEFER_RH_REGISTER(shared_hcd))
+		usb_stop_hcd(shared_hcd);
 err_hcd_driver_start:
 	if (usb_hcd_is_primary_hcd(hcd) && hcd->irq > 0)
 		free_irq(irqnum, hcd);

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

On 26.8.2021 14.14, Kishon Vijay Abraham I wrote:

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.

Signed-off-by: Kishon Vijay Abraham I <redacted>
Suggested-by: Mathias Nyman <redacted>
Tested-by: Chris Chiu <redacted>

Acked-by: Mathias Nyman <redacted>

On Thu, Aug 26, 2021 at 04:44:25PM +0530, Kishon Vijay Abraham I wrote:

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.

Signed-off-by: Kishon Vijay Abraham I <redacted>
Suggested-by: Mathias Nyman <redacted>
Tested-by: Chris Chiu <redacted>
---

I should have noticed this problem before...

This was added in the wrong place.  It needs to come before the 
usb_stop_hcd(hcd) call, because usb_start_hcd(hcd) was run before we failed to 
register the shared hcd's root hub.

Furthermore, I don't think we need to stop the shared hcd at all.  At this 
point, the usb_add_hcd() call for the shared hcd has already returned 
successfully.  The usb_stop_hcd(shared_hcd) callback will be made automatically 
when the shared hcd is unregistered later on, after this function returns an 
error.

Come to think of it, don't we also need to modify the usb_disconnect(&rhdev) 
call in usb_remove_hcd() to handle the case where the root hub wasn't 
registered in the first place because it was deferred?  At the very least, we 
should test the hcd's rh_registered flag before trying to unregister the root 
hub.

Alan Stern

Set "HCD_FLAG_DEFER_RH_REGISTER" to hcd->flags in xhci_run() to defer
registering primary roothub in usb_add_hcd(). This will make sure both
primary roothub and secondary roothub will be registered along with the
second HCD. This is required for cold plugged USB devices to be detected
in certain PCIe USB cards (like Inateck USB card connected to AM64 EVM
or J7200 EVM).

Signed-off-by: Kishon Vijay Abraham I <redacted>
Suggested-by: Mathias Nyman <redacted>
Tested-by: Chris Chiu <redacted>
---
 drivers/usb/host/xhci.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 3618070eba78..7176058c7f3e 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c

@@ -692,6 +692,7 @@ int xhci_run(struct usb_hcd *hcd)
 		if (ret)
 			xhci_free_command(xhci, command);
 	}
+	set_bit(HCD_FLAG_DEFER_RH_REGISTER, &hcd->flags);
 	xhci_dbg_trace(xhci, trace_xhci_dbg_init,
 			"Finished xhci_run for USB2 roothub");
 

-- 
2.17.1

On 26.8.2021 14.14, Kishon Vijay Abraham I wrote:

Set "HCD_FLAG_DEFER_RH_REGISTER" to hcd->flags in xhci_run() to defer
registering primary roothub in usb_add_hcd(). This will make sure both
primary roothub and secondary roothub will be registered along with the
second HCD. This is required for cold plugged USB devices to be detected
in certain PCIe USB cards (like Inateck USB card connected to AM64 EVM
or J7200 EVM).

Signed-off-by: Kishon Vijay Abraham I <redacted>
Suggested-by: Mathias Nyman <redacted>
Tested-by: Chris Chiu <redacted>
---

Acked-by: Mathias Nyman <redacted>