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authorHans de Goede <hdegoede@redhat.com>2012-08-30 09:55:19 +0200
committerGerd Hoffmann <kraxel@redhat.com>2012-08-31 11:58:03 +0200
commita1c3e4b839f8e7ec7f1792b8a11c63ca845aa021 (patch)
tree59744be1de41a0c4982d4d7e45a0ec6a3f2ad4e9
parent7ce86aa1aafaa65e7d3e572873bdf37bdb896f49 (diff)
downloadqemu-arm-a1c3e4b839f8e7ec7f1792b8a11c63ca845aa021.tar.gz
ehci: Schedule async-bh when IAAD bit gets set
After the "ehci: Print a warning when a queue unexpectedly contains packets on cancel" commit. Under certain reproducable conditions I was getting the following message: "EHCI: Warning queue not empty on queue reset". After aprox. 8 hours of debugging I've finally found the cause. The Linux EHCI driver has an IAAD watchdog, to work around certain EHCI hardware sometimes not acknowledging the doorbell at all. This watchdog has a timeout of 10 ms, which is less then the time between 2 runs through the async schedule when async_stepdown is at its highest value. Thus the watchdog can trigger, after which Linux clears the IAAD bit and re-uses the QH. IOW we were not properly detecting the unlink of the qh, due to us missing (ignoring for more then 10 ms) the IAAD command, which triggered the warning. Signed-off-by: Hans de Goede <hdegoede@redhat.com>
-rw-r--r--hw/usb/hcd-ehci.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/hw/usb/hcd-ehci.c b/hw/usb/hcd-ehci.c
index a3aea6debe..3e10977492 100644
--- a/hw/usb/hcd-ehci.c
+++ b/hw/usb/hcd-ehci.c
@@ -1194,6 +1194,15 @@ static void ehci_mem_writel(void *ptr, target_phys_addr_t addr, uint32_t val)
val &= ~USBCMD_FLS;
}
+ if (val & USBCMD_IAAD) {
+ /*
+ * Process IAAD immediately, otherwise the Linux IAAD watchdog may
+ * trigger and re-use a qh without us seeing the unlink.
+ */
+ s->async_stepdown = 0;
+ qemu_bh_schedule(s->async_bh);
+ }
+
if (((USBCMD_RUNSTOP | USBCMD_PSE | USBCMD_ASE) & val) !=
((USBCMD_RUNSTOP | USBCMD_PSE | USBCMD_ASE) & s->usbcmd)) {
if (s->pstate == EST_INACTIVE) {