Messages in this thread | | | Subject | Re: [PATCH] Don't touch USB controllers with MMIO disabled in quirks | From | Benjamin Herrenschmidt <> | Date | Thu, 03 Nov 2005 08:13:54 +1100 |
| |
> But an alternative strategy (which might be very sensible) is to forget > about the handoff entirely, and just shut down the bus master flag > unconditionally. Just make sure that the eventual driver will reset the > controller before it re-enables bus mastering.
Unfortunately, I know quite a few devices (including USB controllers) that will react badly to the bus master flag being just cleared like that. By badly, I mean it ranges from simply ignoring it and happily continuing whatever bus master was being done, to completely screwing up and crapping all over your memory/bus.
> That would seem to be the simplest possible "handoff". The only danger is > that I could imagine that there would be controllers out there that get > really confused (ie "I'm not going to play nice any more") if we shut them > up that way.
I suspect with the IO/MEM enable test fix we did, it shoul work fine in practice for all cases. Let's address the "potential" issues if they happen to show up in real life, which I doubt.
Ben.
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |