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SubjectRe: [PATCH] #2 VIA Rhine stalls: TxAbort handling
On Thu, 16 May 2002, 'Roger Luethi' wrote:

> On Thu, 16 May 2002 18:03:25 +0800, Shing Chuang wrote:
> > As following three error conditions occurred, the VT6102 & VT86C100A
> > chip are designed to shutdown TX for driver to examine the error frame.
> >
> > 1. Tx fifo underrun.
> >
> > 2. Tx Abort (Too many collisions occurred).
> >
> > 3. TxDescriptors status write back error. (Only on VT6102 chip)
>
> Hey, thanks! That's exactly the piece of information I've been looking for.
>
> > All the three conditions caused the TXON bit of CR1 went off. the
> > driver must wait a little while until the bit go off, reset the pointer of
> > [...]
> > do {} while (BYTE_REG_BITS_IS_ON(CR0_TXON,&pMacRegs->byCR0));
>
> The driver "waits a little" in the interrupt handler? How long can that
> take, worst case?

Forever..........^;)
> I don't know of many places where the kernel stops to
> wait for an external device to change some value.
>

Yep... should never wait inside an ISR, to say nothing about
the potential wait-forever.

Even if the chip never breaks, you end up with reports like..
"Strange, I make frisbees when buring CDs while M$ machines do
backups over the network..."

Or, I can't play ".wav" files anymore unless I unplug from the
network...

Stuff has to play together. Sometimes this means you can't get
the maximum-theoretical-possible through-put from your connected
devices.

The worse-case driver is where the programmer decided to turn
interrupts back on in the ISR.... to let higher-priority interrupts
occur... FYI, there are always higher-priority interrupts that
will take the CPU away... you lose big-time.

Cheers,
Dick Johnson

Penguin : Linux version 2.4.18 on an i686 machine (797.90 BogoMips).

Windows-2000/Professional isn't.

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