Subject: Re: Should Alpha PCI code manage latency timers?
To: Thor Lancelot Simon <>
From: Reinoud Zandijk <>
List: tech-kern
Date: 01/24/2005 15:14:39
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Hiya Thor,

On Mon, Jan 24, 2005 at 08:10:07AM -0500, Thor Lancelot Simon wrote:
> The upshot of a rather strange recent thread in netbsd-help (titled
> "got drivers?") was that, at least on some PCI alphas, neither SRM
> nor our MD PCI code set devices' latency timers at all.  A user had
> a machine with two tulips, a pciide, and a QL1040 -- only the 1040
> worked reliably, because the isp driver explicitly whacks the latency
> timer value to 0x40 if it finds it at 0x00.
> The user adjusted the pciide driver to set the latency timer to 0x40
> and all of a sudden he could use the disk and talk on the network at
> the same time without losing packets.
> If SRM isn't going to set the latency timer it seems to me we ought to;
> and not in every device driver, either!

Yikes!!! now that could explain the problems i had with my ohci driver in 
combination with my ide driver i was ranting about some time ago... if such 
a latency timer would indeed result in losing interrupts too then it would 
solve that problem too i hope!

Note that pcictl reports that my troublesome onboard IDE interface indeed 
reports :
    Latency Timer: 0x00
    Maximum Latency: 0x00

as the onboard USB :
    Latency Timer: 0xff		( ??? )
    Maximum Latency: 0x00

So that could well explain the problems they have with eachother....

BTW, its an SRM based DEC PWS 500a



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