Messages in this thread Patch in this message | | | Date | Sat, 12 Apr 2008 21:26:14 +0200 (CEST) | From | Stefan Richter <> | Subject | [PATCH] firewire: fw-ohci: work around generation bug in TI controllers (fix AV/C and more) |
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Unlike the ohci1394 driver, fw-ohci uses the selfIDGeneration field of bus reset packets to determine the generation of incoming requests as per OHCI 1.1 clause 8.4.2.3. This is more precise --- provided that the controller inserts the correct generation. Texas Instruments chips often don't.
This prevented the transmission of response packets, which for example broke AV/C transactions as used when communicating with miniDV cameras and any other AV/C devices.
There is apparently no way to detect and adjust incorrect generations. Therefore we ignore the generation of bus reset packets from TI chips and use the generation of the self ID buffer instead. Alas this is received at a slightly wrong time. In rare cases, this could cause us to not respond to legitimate requests in rare cases, or to respond to expired requests. (The latter is less likely because the bus reset packet AR event is typically handled before the self ID complete event.)
Bug reported by Mladen Kuntner, who was extraordinarily patient while dealing with the driver maintainers. https://bugzilla.redhat.com/show_bug.cgi?id=243081
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de> --- drivers/firewire/fw-ohci.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-)
Index: linux/drivers/firewire/fw-ohci.c =================================================================== --- linux.orig/drivers/firewire/fw-ohci.c +++ linux/drivers/firewire/fw-ohci.c @@ -571,14 +571,22 @@ static __le32 *handle_ar_packet(struct a * generation. We only need this for requests; for responses * we use the unique tlabel for finding the matching * request. + * + * Alas TI chips often emit bus reset packets with a wrong + * generation. As a trade-off, we set the correct generation + * at a slightly incorrect time (in bus_reset_tasklet). */ + if (evt == OHCI1394_evt_bus_reset) { + struct pci_dev *dev = to_pci_dev(ohci->card.device); + + if (dev->vendor != PCI_VENDOR_ID_TI) + ohci->request_generation = (p.header[2] >> 16) & 0xff; - if (evt == OHCI1394_evt_bus_reset) - ohci->request_generation = (p.header[2] >> 16) & 0xff; - else if (ctx == &ohci->ar_request_ctx) + } else if (ctx == &ohci->ar_request_ctx) { fw_core_handle_request(&ohci->card, &p); - else + } else { fw_core_handle_response(&ohci->card, &p); + } return buffer + length + 1; } @@ -1209,6 +1217,7 @@ at_context_transmit(struct context *ctx, static void bus_reset_tasklet(unsigned long data) { struct fw_ohci *ohci = (struct fw_ohci *)data; + struct pci_dev *dev = to_pci_dev(ohci->card.device); int self_id_count, i, j, reg; int generation, new_generation; unsigned long flags; @@ -1285,6 +1294,9 @@ static void bus_reset_tasklet(unsigned l context_stop(&ohci->at_response_ctx); reg_write(ohci, OHCI1394_IntEventClear, OHCI1394_busReset); + if (dev->vendor == PCI_VENDOR_ID_TI) + ohci->request_generation = generation; + /* * This next bit is unrelated to the AT context stuff but we * have to do it under the spinlock also. If a new config rom -- Stefan Richter -=====-==--- -=-- -==-- http://arcgraph.de/sr/
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