EHCI: workaround for MosChip controller bug
This patch (as1489) works around a hardware bug in MosChip EHCI
controllers. Evidently when one of these controllers increments the
frame-index register, it changes the three low-order bits (the
microframe counter) before changing the higher order bits (the frame
counter). If the register is read at just the wrong time, the value
obtained is too low by 8.
When the appropriate quirk flag is set, we work around this problem by
reading the frame-index register a second time if the first value's
three low-order bits are all 0. This gives the hardware a chance to
finish updating the register, yielding the correct value.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Jason N Pitt <jpitt@fhcrc.org>
CC: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/usb/host/ehci-pci.c b/drivers/usb/host/ehci-pci.c
index 8311de7..f4b627d 100644
--- a/drivers/usb/host/ehci-pci.c
+++ b/drivers/usb/host/ehci-pci.c
@@ -224,6 +224,11 @@
pci_dev_put(p_smbus);
}
break;
+ case PCI_VENDOR_ID_NETMOS:
+ /* MosChip frame-index-register bug */
+ ehci_info(ehci, "applying MosChip frame-index workaround\n");
+ ehci->frame_index_bug = 1;
+ break;
}
/* optional debug port, normally in the first BAR */