On Sun, 2 Dec 2001, Benjamin Herrenschmidt wrote: > The question is why DMA would have been disabled in the first place ? > > The kernel is enabling DMA by default on all devices that support it > connected to the Apple IDE interface.
Actually, that is a really good question and I do not know the answer to it :). When I tried to reproduce things by rebooting and letting the iBook sleep and wake up several times, DMA was always enabled. However, before that DMA was disabled and I did not adjust anything with hdparm myself. To give some more information, it is a recent iBook Dual USB and I frequently let it sleep and wake up. My powerctl-scripts do not touch the configuration of the CD-ROM drive. The one thing which repeatedly does not work is persistent mounting, i.e. I have to remount the CD after wakeup. (The IDE driver works O.K., but I always use ide-scsi.) I do not know if this is relevant (it is at least also related to DMA) but maybe someone else does: There is one strange thing about the sound driver. Very infrequently the iBook would make strange obnoxious noises after waking up from sleep. Closing the lid, waiting, opening the lid again helped. Once I also observed that the usage count of the sound driver module was screwed (up to 3, even though no process was using sound devices), so it could not be unloaded. (The screwed usage count was with some earlier kernel, though.) Greetings, Lukas
