Re: EISA ID for PnP modem and resource allocation
From: Adam Belay (ambx1_at_neo.rr.com)
Date: 12/29/03
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Date: Mon, 29 Dec 2003 22:50:37 +0000 To: Amit Gurdasani <amitg@alumni.cmu.edu>
On Tue, Dec 30, 2003 at 03:59:16AM +0400, Amit Gurdasani wrote:
> :Without special hardware modifications, it is usually unsafe to share irqs
> :between isa devices.
>
> Ah. So 2.4's behavior was broken then?
Perhaps in this case.
>
> :> The reason I ask is that I also have a jumpered SB16 on IRQ 5, and loading
> :> the 8250 driver before the snd_sb16 driver results in the SB16's IRQ being
> :> allocated for the modem, which prevents the SB16 driver from loading.
> :> Loading the SB16 driver first results in resource starvation for the modem,
> :> and the 8250 driver is only able to set up the onboard serial ports ttyS0
> :> and ttyS1.
> :
> :You may want to try changing the jumper on your SB16 to allow for PnP
> :autoconfiguration.
>
> It's a pre-PnP SB16 from 1994, as far as I can tell -- IRQ, I/O port and DMA
> channels can be set only by setting jumpers. I suppose I could pull the card
> out and set its IRQ setting to something the modem won't claim.
Because of detection limitations in legacy hardware, you may have to notify the
Plug and Play Layer that your device is using irq 5. Booting with the parameter
pnp_reserve_irq=5 will prevent resource conflicts with the legacy SB16 device.
>
> :> In the meantime, I'm using the isapnptools to set up the modem with IRQ 4
> :> before loading either driver. The result is that the SB16 driver gets IRQ 5
> :> as needed, and ttyS0 is set up with IRQ 0 (is this OK?), but I'd really like
> :> to use the kernel ISA PnP support.
> :
> :Could I please see a copy of your /proc/interrupts.
>
> CPU0
> 0: 314288 XT-PIC timer
> 1: 1024 XT-PIC i8042
> 2: 0 XT-PIC cascade
> 5: 7444 XT-PIC SoundBlaster
> 8: 1 XT-PIC rtc
> 9: 4675 XT-PIC ide2
> 10: 41 XT-PIC eth0
> 11: 89930 XT-PIC i91u
> 12: 10092 XT-PIC i8042
> 15: 57 XT-PIC ide1
> NMI: 0
> LOC: 0
> ERR: 0
> MIS: 0
>
> Apart from these, dmesg output shows these IRQs allocated:
>
> ttyS0 at I/O 0x3f8 (irq = 0) is a 16550A
> ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A
> ttyS2 at I/O 0x3e8 (irq = 4) is a 16550A
> parport0: irq 7 detected
Hmm, it shouldn't be reporting irq 0. The probbing code may be confused.
I would guess it is on irq 4.
>
> Additionally, pnpdump says the modem can only claim an IRQ line from among
> 3, 4, 5, 7, 9, 10, 11, 12 or 15 in various configurations.
It appears that you have an unresolvable resource conflict. I'm working on
a more flexable resource manager for the 2.7 kernel. For now, I recommend that
you disable one of your serial ports in your BIOS configuration interface and
try booting with pnp_reserve_irq=5.
Alternatively you could try enabling PnPBIOS support. There's a slight chance
that the pci code will reroute ide2 to 14 (assuming ide2 is pci), leaving room
for your modem on 9. You'll still need to reserve irq 5 as stated above.
Thanks,
Adam
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- Previous message: Go Taniguchi: "Re: Adaptec/DPT I2O Option Omitted From Linux 2.6.0 Kernel Configuration Tool"
- Maybe in reply to: Amit Gurdasani: "EISA ID for PnP modem and resource allocation"
- Next in thread: Amit Gurdasani: "Re: EISA ID for PnP modem and resource allocation"
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