Subject: Re: More IRQ questions

From: Philip Blundell <[email-masked]>
Date: Sun, 13 Aug 2000 17:36:48 +0100

>What confuses me is asignation of on-board southbridge devices, like USB,
>which is given a 139 IRQ, then Linux assigns IRQ (139-128)+16 -> 27
>that would be a IRQ_DMA2. This makes no sense to me. In this same sheets
>Chalice says it assigns USB an ISA IRQ, number 11. This would lead to
>a IRQ (139-128) -> 11, seems righter.

The code you are looking at is out of date.  On footbridge platforms the ISA 
irqs used to be in the range 16..31.  I don't recall exactly when this was 
changed, but I don't really expect 2.2 kernels to work very well on the CATS 
without some extra patches.  You would be better off with 2.4.  

>3) Bios Interrupt Number x: "BIRQ x"

I don't think this would do any harm, though I can't see that it buys you very 
much either.

>Please, Phil,  tell me also about removing slot 4...

To be honest I don't really remember.  It seems most likely that this is 
indeed just a mistake, but it won't do any harm since that slot number will 
never crop up.  I'll check the code when I get time to make sure.

>What is IRQ_32

The 32-bit "IRQ" mode (not to be confused with IRQ 32...).  The processor is 
only in this mode for a very few instructions and interrupts should be 
disabled.

p.

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From: David Aparicio <[email-masked]>
Date: Mon, 14 Aug 2000 10:35:39 +0200

> without some extra patches.  You would be better off with 2.4.

I just have a space proble, 2.4 doen't fit in a 512 KB FLASH, so I will need to
download every time I boot (disk and net boot from FW still unusable... I only
have a 38400 serial link :-(). That was the reason I was using 2.2, but it seems
it's time to change...

> I don't think this would do any harm, though I can't see that it buys you very

You are right :-)

> only in this mode for a very few instructions and interrupts should be

Ok. What I plan to do is to support interrupt handling on FW (althought I don't
need
for drivers), unmask them manually (special command), and see which one and why
is hammering... That way I will avoid to download 500 Kbytes of code for every
test,
(It would break my nerves for sure...). After that Linux 2.4.x should start up
fine...

I will be on holidays for the next weeks, so I will check this on early
September...

Happy hacking!!