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From:   Sasha Levin <sashal@kernel.org>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc:     Longfang Liu <liulongfang@huawei.com>,
        Alan Stern <stern@rowland.harvard.edu>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: [PATCH 4.4 098/135] USB: ehci: reopen solution for Synopsys HC bug
Date:   Mon, 29 Jun 2020 11:52:32 -0400
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From: Longfang Liu <liulongfang@huawei.com>

commit 1ddcb71a3edf0e1682b6e056158e4c4b00325f66 upstream.

A Synopsys USB2.0 core used in Huawei Kunpeng920 SoC has a bug which
might cause the host controller not issuing ping.

Bug description:
After indicating an Interrupt on Async Advance, the software uses the
doorbell mechanism to delete the Next Link queue head of the last
executed queue head. At this time, the host controller still references
the removed queue head(the queue head is NULL). NULL reference causes
the host controller to lose the USB device.

Solution:
After deleting the Next Link queue head, when has_synopsys_hc_bug set
to 1，the software can write one of the valid queue head addresses to
the ASYNCLISTADDR register to allow the host controller to get
the valid queue head. in order to solve that problem, this patch set
the flag for Huawei Kunpeng920

There are detailed instructions and solutions in this patch:
commit 2f7ac6c19997 ("USB: ehci: add workaround for Synopsys HC bug")

Signed-off-by: Longfang Liu <liulongfang@huawei.com>
Cc: stable <stable@vger.kernel.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/1591588019-44284-1-git-send-email-liulongfang@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/usb/host/ehci-pci.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/usb/host/ehci-pci.c b/drivers/usb/host/ehci-pci.c
index 2a5d2fd76040c..33e9ed7fe0266 100644
--- a/drivers/usb/host/ehci-pci.c
+++ b/drivers/usb/host/ehci-pci.c
@@ -229,6 +229,13 @@ static int ehci_pci_setup(struct usb_hcd *hcd)
 		ehci_info(ehci, "applying MosChip frame-index workaround\n");
 		ehci->frame_index_bug = 1;
 		break;
+	case PCI_VENDOR_ID_HUAWEI:
+		/* Synopsys HC bug */
+		if (pdev->device == 0xa239) {
+			ehci_info(ehci, "applying Synopsys HC workaround\n");
+			ehci->has_synopsys_hc_bug = 1;
+		}
+		break;
 	}
 
 	/* optional debug port, normally in the first BAR */
-- 
2.25.1