Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752486Ab0BNRrP (ORCPT ); Sun, 14 Feb 2010 12:47:15 -0500 Received: from einhorn.in-berlin.de ([192.109.42.8]:41351 "EHLO einhorn.in-berlin.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752388Ab0BNRrO convert rfc822-to-8bit (ORCPT ); Sun, 14 Feb 2010 12:47:14 -0500 X-Envelope-From: stefanr@s5r6.in-berlin.de Date: Sun, 14 Feb 2010 18:46:27 +0100 (CET) From: Stefan Richter Subject: [PATCH 1/4 resend] firewire: ohci: work around cycle timer bugs on VIA controllers To: linux-kernel@vger.kernel.org cc: linux1394-devel@lists.sourceforge.net In-Reply-To: Message-ID: References: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; CHARSET=iso-8859-1 Content-Transfer-Encoding: 8BIT Content-Disposition: INLINE Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3723 Lines: 108 Date: Wed, 20 Jan 2010 09:58:02 +0100 From: Clemens Ladisch VIA controllers sometimes return an inconsistent value when reading the isochronous cycle timer register. To work around this, read the register multiple times and add consistency checks. Signed-off-by: Clemens Ladisch Reported-by: Pieter Palmers Reported-by: H?kan Johansson Signed-off-by: Stefan Richter --- drivers/firewire/ohci.c | 52 ++++++++++++++++++++++++++++++++++++++-- 1 file changed, 49 insertions(+), 3 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 @@ -192,6 +192,7 @@ struct fw_ohci { bool use_dualbuffer; bool old_uninorth; bool bus_reset_packet_quirk; + bool iso_cycle_timer_quirk; /* * Spinlock for accessing fw_ohci data. Never call out of @@ -1794,14 +1795,57 @@ static int ohci_enable_phys_dma(struct f #endif /* CONFIG_FIREWIRE_OHCI_REMOTE_DMA */ } +static inline u32 cycle_timer_ticks(u32 cycle_timer) +{ + u32 ticks; + + ticks = cycle_timer & 0xfff; + ticks += 3072 * ((cycle_timer >> 12) & 0x1fff); + ticks += (3072 * 8000) * (cycle_timer >> 25); + return ticks; +} + static u64 ohci_get_bus_time(struct fw_card *card) { struct fw_ohci *ohci = fw_ohci(card); - u32 cycle_time; + u32 c0, c1, c2; + u32 t0, t1, t2; + s32 diff01, diff12; u64 bus_time; - cycle_time = reg_read(ohci, OHCI1394_IsochronousCycleTimer); - bus_time = ((u64)atomic_read(&ohci->bus_seconds) << 32) | cycle_time; + if (!ohci->iso_cycle_timer_quirk) { + 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, + * 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 + * cycleCount field is not incremented for about 60 ns. + * + * To catch these, we read the register three times and ensure + * that the difference between each two consecutive reads is + * approximately the same, i.e., less than twice the other. + * Furthermore, any negative difference indicates an error. + * (A PCI read should take at least 20 ticks of the 24.576 MHz + * timer to execute, so we have enough precision to compute the + * ratio of the differences.) + */ + do { + c0 = reg_read(ohci, OHCI1394_IsochronousCycleTimer); + c1 = reg_read(ohci, OHCI1394_IsochronousCycleTimer); + c2 = reg_read(ohci, OHCI1394_IsochronousCycleTimer); + t0 = cycle_timer_ticks(c0); + t1 = cycle_timer_ticks(c1); + t2 = cycle_timer_ticks(c2); + diff01 = t1 - t0; + diff12 = t2 - t1; + } while (diff01 <= 0 || diff12 <= 0 || + diff01 / diff12 >= 2 || diff12 / diff01 >= 2); + } + bus_time = ((u64)atomic_read(&ohci->bus_seconds) << 32) | c2; return bus_time; } @@ -2503,6 +2547,8 @@ 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; + ar_context_init(&ohci->ar_request_ctx, ohci, OHCI1394_AsReqRcvContextControlSet); -- Stefan Richter -=====-==-=- --=- -===- http://arcgraph.de/sr/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/