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From: Stefan Richter on 14 Feb 2010 12:50
Discussed in "read_cycle_timer backwards for sub-cycle 0000, 0001",
http://thread.gmane.org/gmane.linux.kernel.firewire.devel/13704

Known bad controllers:
ALi M5271, listed by lspci as M5253 [10b9:5253]
NEC OrangeLink [1033:00cd] (rev 03)
NEC uPD72874 [1033:00f2] (rev 01)
VIA VT6306 [1106:3044] (rev 46)
VIA VT6308P, listed by lspci as rev c0

Reported-by: Pieter Palmers <pieterp(a)joow.be>
Reported-by: H�kan Johansson <f96hajo(a)chalmers.se>
Reported-by: Clemens Ladisch <clemens(a)ladisch.de>
Signed-off-by: Stefan Richter <stefanr(a)s5r6.in-berlin.de>
---
drivers/firewire/ohci.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)

Index: linux-2.6.33-rc8/drivers/firewire/ohci.c
===================================================================
--- linux-2.6.33-rc8.orig/drivers/firewire/ohci.c
+++ linux-2.6.33-rc8/drivers/firewire/ohci.c
@@ -1817,13 +1817,14 @@ static u64 ohci_get_bus_time(struct fw_c
c2 = reg_read(ohci, OHCI1394_IsochronousCycleTimer);
} else {
/*
- * VIA controllers have two bugs when updating the iso cycle
- * timer register:
- * 1) When the lowest six bits are wrapping around to zero,
+ * Some controllers exhibit one or more of the following bugs
+ * when updating the iso cycle timer register:
+ * - When the lowest six bits are wrapping around to zero,
* a read that happens at the same time will return garbage
* in the lowest ten bits.
- * 2) When the cycleOffset field wraps around to zero, the
+ * - When the cycleOffset field wraps around to zero, the
* cycleCount field is not incremented for about 60 ns.
+ * - Occasionally, the entire register reads zero.
*
* To catch these, we read the register three times and ensure
* that the difference between each two consecutive reads is
@@ -2547,7 +2548,9 @@ static int __devinit pci_probe(struct pc
#endif
ohci->bus_reset_packet_quirk = dev->vendor == PCI_VENDOR_ID_TI;

- ohci->iso_cycle_timer_quirk = dev->vendor == PCI_VENDOR_ID_VIA;
+ ohci->iso_cycle_timer_quirk = dev->vendor == PCI_VENDOR_ID_AL ||
+ dev->vendor == PCI_VENDOR_ID_NEC ||
+ dev->vendor == PCI_VENDOR_ID_VIA;

ar_context_init(&ohci->ar_request_ctx, ohci,
OHCI1394_AsReqRcvContextControlSet);

--
Stefan Richter
-=====-==-=- --=- -===-
http://arcgraph.de/sr/

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