Alan Cox wrote: > On Thu, 8 Nov 2007 22:46:22 -0500 > Jeff Garzik <jeff@xxxxxxxxxx> wrote: > > >> On Thu, Nov 08, 2007 at 10:29:37PM -0500, Mark Lord wrote: >> >>> And I might even privately patch my own kernels to map the ACHI BAR >>> in the cases where the BIOS didn't... >>> >> The inability to do this in the general case is the main reason why >> AHCI was not unconditionally enabled, even in IDE mode, when it was >> originally added... :/ >> > > We've done it all the time for various devices without problems (eg S3 > video cards). I'd like to see it go in - although perhaps attached to a > force_ahci boot param initially > There is one problem with force enabling ahci. You'll loose the CDROM on Dell laptops. Prior to force-enabling ahci there is one "device" that sees the 2 sata channels, and the 2 ide channels. When you force-enable ahci, this device becomes the ahci controller (it changes the device id), and the IDE controller will appear as a separate new device (with another device id), but it is disabled. There are registers on the ICH7 that allows you to set enabled/disabled status, but according to the documentation you should not enable a device after it has been disabled. In practice I couldn't get the CDROM to get re-enabled: * either nothing happend * spurious irqs were sent that nobody handles, unless I used irq=poll; but still no cdrom. Force-enabling AHCI, and not trying to enable the CDROM works, although I occasionally got NCQ errors. For a (long) discussion see this thread on the powertop mailing list: http://www.bughost.org/pipermail/power/2007-June/000533.html http://www.bughost.org/pipermail/power/2007-June/000573.html And there is also another slightly different approach: http://mjg59.livejournal.com/76062.html Best regards, --Edwin - 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
