linux-kernel - Re: [PATCH update] firewire: fw-ohci: work around generation bug in TI controllers (fix AV/C and more)

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Date:	Mon, 14 Apr 2008 13:30:22 -0400
From:	Jarod Wilson <jwilson@...hat.com>
To:	linux1394-devel@...ts.sourceforge.net
Cc:	Stefan Richter <stefanr@...6.in-berlin.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH update] firewire: fw-ohci: work around generation bug in TI controllers (fix AV/C and more)

On Saturday 12 April 2008 04:31:25 pm Stefan Richter wrote:
> 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 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@...6.in-berlin.de>
> ---
>
> update: use a quirk flag for simpler code

The work-around looks good to me, just one question.

> @@ -2360,6 +2369,8 @@ pci_probe(struct pci_dev *dev, const str
>  	ohci->old_uninorth = dev->vendor == PCI_VENDOR_ID_APPLE &&
>  			     dev->device == PCI_DEVICE_ID_APPLE_UNI_N_FW;
>  #endif
> +	ohci->bus_reset_packet_quirk = dev->vendor == PCI_VENDOR_ID_TI;
> +

I have a few cards with PCI_VENDOR_ID_CREATIVE with a TI TSB41AB2 chip on 'em 
(SoundBlaster Audigy w/FireWire port). I've not had any issues on any of the 
cards I've got, but do we want to add them to the work-around list just to be 
safe?


-- 
Jarod Wilson
jwilson@...hat.com
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