[RFC PATCH] rxerr patch

[Andy Green]

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Somebody in the thread at some point said:

| Looking at the interrupt priority arbitration scheme in the s3c2442
| datasheet, it seems we could play a trick and elevate arbiter 4 above
| arbiter 3 at arbiter 6 (ARB_SEL6 <- 3).  At the moment, we just use
| default priority throughout, but that should allow GPS UART to interrupt
| this long SDI service action.
|
| It sounds good because USB host and device interrupt is also in arbiter
| 3 along with GPS UART, these should have higher priority than the fully
| synchronous SDI you would think.

I just posted a patch "[PATCH] fix-gta02-irq-arbiter-priority.patch" on
the list that does this and disables rotation in the arbitrators.

I tested it and still got occasional GPS overrun indication

[  372.575000] rxerr: port=1 ch=0x6e, rxs=0x00000001
[  976.240000] rxerr: port=1 ch=0x6e, rxs=0x00000001
[ 1002.750000] rxerr: port=1 ch=0x20, rxs=0x00000001

but only when I was catting /dev/ttySAC1.

Maybe someone can gve it a whirl and see if it helps GPS overrun
situation or breaks reliability of interrupt service somewhere else.

- -Andy
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