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SubjectRe: [PATCH] IBM Lanstreamer bugfixes

On Fri, 18 Jan 2002, Alan Cox wrote:

> > BTW, I don't know what PCI posting effects are...
> Ok given
> writel(foo, dev->reg);
> udelay(5);
> writel(bar, dev->reg);
> The pci bridge is at liberty to delay the first write until the second or a
> read from that device comes along (and wants to do so to merge bursts). It
> tends to bite people
> - When they do a write to clear the IRQ status and don't do
> a read so they keep handling lots of phantom level triggered
> interrupts.

Not only (when the write is intended to clear some interrupt condition).

As the actual clear of the interrupt condition is delayed, then it may
just also clear a sub-sequent condition and this condition may be missed
by the driver interrupt routine. Due to this a race, interrupt stall can

> - When there is a delay (reset is common) that has to be observed
> - At the end of a DMA transfer when people unmap stuff early
> and the "stop the DMA" command got delayed


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