PXA168 + 88W8686 SDIO interrupt troubles

[James Cameron]

On Fri, Jun 10, 2022 at 11:12:02PM -0700, Doug Brown wrote:
> Well, I got it working well enough that I'm satisfied!

Yay!  Well done.

> On 6/9/2022 2:49 PM, Doug Brown wrote:
> 
> > 2) The sd8xxx driver's IRQ handler increments a counter and wakes the
> >     main thread to do the work, so the SDHC host controller's interrupt
> >     gets unmasked quickly, whereas libertas does more handling in the IRQ
> >     handler before returning and allowing the interrupt to be unmasked.
> 
> Hacking the libertas driver to acknowledge the interrupt in the host
> controller immediately after clearing the 88W8686's interrupt register
> definitely helped, but I still ran into missing interrupts when there
> was a lot of activity, like downloading a big file.
> 
> After lots of experimentation, I also changed the libertas driver to re-read
> the interrupt status register from the 88W8686 after re-enabling
> the interrupts in the host controller. That caused it to stop missing
> interrupts, which makes no sense, but it fixed it. [...]

That sounds familiar, but hard to be sure given the elapsed time.

We certainly found a few situations where (how shall I put it) vendor
drivers may have driven the testing of the silicon.  We had the
advantage of being able to ask the vendor about it, but no longer.