Date: Mon, 02 Apr 2001 11:33:58 -0800 (PDT) From: John Baldwin <jhb@FreeBSD.org> To: Alfred Perlstein <bright@wintelcom.net> Cc: qa@FreeBSD.org, mobile@FreeBSD.org, John Reynolds <jjreynold@home.com>, Mike Smith <msmith@FreeBSD.org>, Warner Losh <imp@harmony.village.org> Subject: Re: followup to problems with 4.3-RC1 for laptops Message-ID: <XFMail.010402113358.jhb@FreeBSD.org> In-Reply-To: <20010402104419.U813@fw.wintelcom.net>
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On 02-Apr-01 Alfred Perlstein wrote:
> * John Baldwin <jhb@FreeBSD.ORG> [010402 10:37] wrote:
>>
>> On 31-Mar-01 Warner Losh wrote:
>> > In message <XFMail.010330150116.jhb@FreeBSD.org> John Baldwin writes:
>> >: That is easy enough to work around, just have the cardbus code mask out
>> >: INTR_FAST in its bus_setup_intr and bus_teardown_intr and it will work
>> >: fine.
>> >: This will hurt sio(4) performance some however, but if fast interrupts
>> >: are a
>> >: problem for cardbus you can always turn them off.
>> >
>> > The problem isn't FAST interrupts with cardbus. The problem is that
>> > fast interrupts can't be shared. I don't think sio does anything that
>> > requires a fast interrupt, except for the latency issues for the 16550
>> > uarts. They can't tolerate the latency we have in non-fast interrupts
>> > in current :-(.
>>
>> I realize that fast interrupts can't be shared, so they are problematic in
>> that
>> regard, and you can still mask out INTR_FAST and INTR_EXCL if you wish in
>> the
>> bus layer so that the attaching device doesn't have to special case its code
>> but can instead basically say what its desires are and let the bus decide if
>> all of them can be satisified or not.
>
> Shouldn't the device be able to specify an all-or-nothing request?
>
> Perhaps something that needs fast interrupts will cause much hair
> pulling if it doesn't get one becasue of latency issues messing up
> the hardware. If the bus didn't grant a fast interrupt it could then
> declien to attach, perhaps spitting out a meaningful error message
> at the same time.
True, no need for an error message, but I suppose one could do something like
this then:
if (BUS_SETUP_INTR(..., INTR_FOO | INTR_FAST, ...) != 0) {
error = BUS_SETUP_INTR(..., INTR_FOO, ...);
if (error)
return (error);
}
> My apologies if this has already been brought up.
No, it was also something kicking around in my head, but I didn't mention it.
Wasn't sure if that was an implied condition of bus_setup_intr().
--
John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/
PGP Key: http://www.baldwin.cx/~john/pgpkey.asc
"Power Users Use the Power to Serve!" - http://www.FreeBSD.org/
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