On Fri, Apr 9, 2010 at 4:12 AM, Tim Small <tim@xxxxxxxxxxxxxxxx> wrote: > Robert Hancock wrote: >> We can detect an AHCI-capable Intel chipsets (in most cases anyway), >> but problem is that a lot of systems with such chipsets, especially >> laptops, unfortunately have no way to actually put the controller into >> AHCI mode (no BIOS option for it). We could whine about it, but in a >> lot of cases there's not much that can be done about it.. >> > > I have a couple of machines with those BIOSes, and apart from the fact > that the Intel ICH datasheets say something like "none but the saintly > BIOS writers shall program this register", it does seem to be possible > to put an ICH9R into AHCI mode using setpci and the fake hot plug driver... In some cases it's likely doable - though you'd likely want to do it as a PCI quirk, so that it gets detected as an AHCI device in the first place rather than having to change it later. > > I just wondered what the potential pitfalls might be of doing this? > Obviously you wouldn't want to be doing anything with the controller at > the time that you change it's mode. Is there also the risk of the > bloody bios fiddling with the device after the OS has booted (and then > getting surprised about it no longer being in piix mode)? Some laptop BIOSes do try to access the controller at certain points, like suspend or powerdown (presumably to make sure the drive heads are unloaded or something) - we've run into problems in the past when the controller was disabled at points where the BIOS didn't expect it to be and it was trying to poke at it, causing a big delay until it finally gave up. For reasons like that we likely couldn't do it in the general case. We could provide it as a disabled-by-default feature, where if someone enables it and it breaks they get to keep both pieces.. -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
