Date: Thu, 29 Dec 2005 17:03:12 +0100
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From: =?iso-8859-1?Q?Burkhard=20Sch=F6lpen?= <bschoelpen@web.de>
To: PaulFulghum <paulkf@microgate.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: PCI DMA burst delay
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>Paul Fulghum <paulkf@microgate.com> schrieb am 29.12.05 16:30:20:
>
>Burkhard Sch?lpen wrote:
>> ... in the (rarely) faulty case, the 2nd burst only starts
>> after another delay of about 600ns, which is too late
>
>Looking at the PCI 2.3 specification,
>arbitration latency on the order of a microsecond
>or two does not seem excessive for a 33MHz bus.

Okay, then I think I have to figure out, why I cannot get longer bursts than 512 Bits...does anybody have a clue how I can handle that?

>> ... I deactivated all other pci devices that could disturb the transfers?
>
>Are you accessing registers on your device
>during the DMA transfers? If so, the CPU is
>acting as a PCI master that could delay granting
>the bus to your device.

No, I just made sure that not. There are no register accesses during dma transfer. The driver sends the application to sleep until an interrupt signals the completeness. 

Kind regards,
Burkhard

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