linux-kernel - [RESEND PATCH v2 2/2] xhci: Set HCD flag to defer primary roothub registration

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Date:   Tue, 10 May 2022 14:46:30 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Alan Stern <stern@...land.harvard.edu>
CC:     Kishon Vijay Abraham I <kishon@...com>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <stable@...r.kernel.org>
Subject: [RESEND PATCH v2 2/2] xhci: Set HCD flag to defer primary roothub registration

Set "HCD_FLAG_DEFER_RH_REGISTER" to hcd->flags in xhci_run() to defer
registering primary roothub in usb_add_hcd() if xhci has two roothubs.
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).

This patch has been added and reverted earier as it triggered a race
in usb device enumeration.
That race is now fixed in 5.16-rc3, and in stable back to 5.4
commit 6cca13de26ee ("usb: hub: Fix locking issues with address0_mutex")
commit 6ae6dc22d2d1 ("usb: hub: Fix usb enumeration issue due to address0
race")

[minor rebase change, and commit message update -Mathias]
CC: stable@...r.kernel.org # 5.4+
Suggested-by: Mathias Nyman <mathias.nyman@...ux.intel.com>
Tested-by: Chris Chiu <chris.chiu@...onical.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
---
 drivers/usb/host/xhci.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 25b87e99b4dd..2be38d9de8df 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -696,6 +696,8 @@ int xhci_run(struct usb_hcd *hcd)
 	xhci_dbg_trace(xhci, trace_xhci_dbg_init,
 			"Finished xhci_run for USB2 roothub");

+	set_bit(HCD_FLAG_DEFER_RH_REGISTER, &hcd->flags);
+
 	xhci_create_dbc_dev(xhci);

 	xhci_debugfs_init(xhci);
-- 
2.17.1