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authorAlan Stern <stern@rowland.harvard.edu>2011-10-12 10:39:14 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2011-10-18 13:49:33 -0700
commit68aa95d5d4de31c9348c1628ffa85c805305ebc5 (patch)
tree7782dad26b9672be03b78a70cae1105f395dafe2 /drivers/usb/host/ehci-sched.c
parent91960c2ef095c4b0744349e80a933921cbdcfd6e (diff)
downloadlinux-stericsson-68aa95d5d4de31c9348c1628ffa85c805305ebc5.tar.gz
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>
Diffstat (limited to 'drivers/usb/host/ehci-sched.c')
-rw-r--r--drivers/usb/host/ehci-sched.c30
1 files changed, 25 insertions, 5 deletions
diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index 488151bb45cb..2e829fae6482 100644
--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -36,6 +36,27 @@
static int ehci_get_frame (struct usb_hcd *hcd);
+#ifdef CONFIG_PCI
+
+static unsigned ehci_read_frame_index(struct ehci_hcd *ehci)
+{
+ unsigned uf;
+
+ /*
+ * The MosChip MCS9990 controller updates its microframe counter
+ * a little before the frame counter, and occasionally we will read
+ * the invalid intermediate value. Avoid problems by checking the
+ * microframe number (the low-order 3 bits); if they are 0 then
+ * re-read the register to get the correct value.
+ */
+ uf = ehci_readl(ehci, &ehci->regs->frame_index);
+ if (unlikely(ehci->frame_index_bug && ((uf & 7) == 0)))
+ uf = ehci_readl(ehci, &ehci->regs->frame_index);
+ return uf;
+}
+
+#endif
+
/*-------------------------------------------------------------------------*/
/*
@@ -481,7 +502,7 @@ static int enable_periodic (struct ehci_hcd *ehci)
/* posted write ... PSS happens later */
/* make sure ehci_work scans these */
- ehci->next_uframe = ehci_readl(ehci, &ehci->regs->frame_index)
+ ehci->next_uframe = ehci_read_frame_index(ehci)
% (ehci->periodic_size << 3);
if (unlikely(ehci->broken_periodic))
ehci->last_periodic_enable = ktime_get_real();
@@ -1408,7 +1429,7 @@ iso_stream_schedule (
goto fail;
}
- now = ehci_readl(ehci, &ehci->regs->frame_index) & (mod - 1);
+ now = ehci_read_frame_index(ehci) & (mod - 1);
/* Typical case: reuse current schedule, stream is still active.
* Hopefully there are no gaps from the host falling behind
@@ -2275,7 +2296,7 @@ scan_periodic (struct ehci_hcd *ehci)
*/
now_uframe = ehci->next_uframe;
if (ehci->rh_state == EHCI_RH_RUNNING) {
- clock = ehci_readl(ehci, &ehci->regs->frame_index);
+ clock = ehci_read_frame_index(ehci);
clock_frame = (clock >> 3) & (ehci->periodic_size - 1);
} else {
clock = now_uframe + mod - 1;
@@ -2454,8 +2475,7 @@ restart:
|| ehci->periodic_sched == 0)
break;
ehci->next_uframe = now_uframe;
- now = ehci_readl(ehci, &ehci->regs->frame_index) &
- (mod - 1);
+ now = ehci_read_frame_index(ehci) & (mod - 1);
if (now_uframe == now)
break;