Re: [PATCH 03/19 v2] Staging: xgifb: Remove LCDA detection in xgifb_probe().
El 09/07/12 20:39, Greg KH escribió: On Fri, Jul 06, 2012 at 12:40:38PM +0200, Miguel Gómez wrote: The piece of code that checks for LCDA in xgifb_probe() just checks for some register values but doesn't really do anything in response to them (the actions that should be executed are commented). As nothing is really being done, the code can be safely removed. Are you sure? Some devices (foolish ones that is) need registers read to work properly as that is part of their start-up logic. Yeah, it doesn't seem to make sense, but hardware designers usually have good reasons for doing this type of thing. Or at least they think they do :) Weird... I didn't expect that some devices might need those reads to work properly... I'm writing down that comment for the future ;) So have you tested the device after this change and it all works properly? You do have this device, right? I have an XGI Z7 card that I use for testing, and it doesn't require those reads to work properly, despite I don't have a Z9 or Z11 to test. But according to Aaro's comment, it seems that the patch is safe as these register reads don't have any effect. Regards! -- Miguel Gómez Igalia - http://www.igalia.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 03/19 v2] Staging: xgifb: Remove LCDA detection in xgifb_probe().
On Fri, Jul 06, 2012 at 12:40:38PM +0200, Miguel Gómez wrote: > The piece of code that checks for LCDA in xgifb_probe() just checks for some > register values but doesn't really do anything in response to them (the > actions > that should be executed are commented). > As nothing is really being done, the code can be safely removed. Are you sure? Some devices (foolish ones that is) need registers read to work properly as that is part of their start-up logic. Yeah, it doesn't seem to make sense, but hardware designers usually have good reasons for doing this type of thing. Or at least they think they do :) So have you tested the device after this change and it all works properly? You do have this device, right? thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 03/19 v2] Staging: xgifb: Remove LCDA detection in xgifb_probe().
Hi, On Mon, Jul 09, 2012 at 11:39:47AM -0700, Greg KH wrote: > On Fri, Jul 06, 2012 at 12:40:38PM +0200, Miguel Gómez wrote: > > The piece of code that checks for LCDA in xgifb_probe() just checks for some > > register values but doesn't really do anything in response to them (the > > actions > > that should be executed are commented). > > As nothing is really being done, the code can be safely removed. > > Are you sure? Some devices (foolish ones that is) need registers read > to work properly as that is part of their start-up logic. Yeah, it > doesn't seem to make sense, but hardware designers usually have good > reasons for doing this type of thing. Or at least they think they do :) Those registers (CR 0x30..0x38) are scratch registers, so reading them should have no side effects in the device side. I think it's safe to delete that code. A. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
