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[PATCH v2 2/2] hw: usb: hcd-ohci: check for processed TD before retire

From: P J P
Subject: [PATCH v2 2/2] hw: usb: hcd-ohci: check for processed TD before retire
Date: Tue, 15 Sep 2020 23:52:59 +0530

From: Prasad J Pandit <pjp@fedoraproject.org>

While servicing OHCI transfer descriptors(TD), ohci_service_iso_td
retires a TD if it has passed its time frame. It does not check if
the TD was already processed once and holds an error code in TD_CC.
It may happen if the TD list has a loop. Add check to avoid an
infinite loop condition.

Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
 hw/usb/hcd-ohci.c | 4 ++++
 1 file changed, 4 insertions(+)

Update v2: one patch for loop issue
  -> https://lists.nongnu.org/archive/html/qemu-devel/2020-09/msg05145.html

diff --git a/hw/usb/hcd-ohci.c b/hw/usb/hcd-ohci.c
index 9dc59101f9..8b912e95d3 100644
--- a/hw/usb/hcd-ohci.c
+++ b/hw/usb/hcd-ohci.c
@@ -691,6 +691,10 @@ static int ohci_service_iso_td(OHCIState *ohci, struct 
ohci_ed *ed,
            the next ISO TD of the same ED */
+        if (OHCI_CC_DATAOVERRUN == OHCI_BM(iso_td.flags, TD_CC)) {
+            /* avoid infinite loop */
+            return 1;
+        }
         OHCI_SET_BM(iso_td.flags, TD_CC, OHCI_CC_DATAOVERRUN);
         ed->head &= ~OHCI_DPTR_MASK;
         ed->head |= (iso_td.next & OHCI_DPTR_MASK);

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