On 13.02.2010, at 09:02, Rob Landley wrote: > The -hda, -hdb, -hdc, and -hdd command line options for g3beige don't match > the order the kernel assigns the drives. > > The reason is that the Linux kernel always initializes the cmd646 driver > before the pmac driver, thus if there's a cmd646 it gets /dev/hda and > /dev/hdb, and the pmac gets /dev/hdc and /dev/hdb. > > If you only supply an -hda (and/or -hdb) with no -hdc or -hdd, then the > cmd646 > driver never attaches to anything and only the pmac controller shows up, thus > -hda and -hdb set /dev/hda and /dev/hdb. But if you specify a -hdc it shows > up as /dev/hda every time, and kicks the -hda entry to /dev/hdc. > > Note that neither the kernel's CONFIG_BLK_DEV_IDE_PMAC_ATA100FIRST nor > CONFIG_IDEPCI_PCIBUS_ORDER made any difference, because those affect multiple > devices handled by the same driver, and this is a static driver > initialization > order issue. When you statically link in both drivers, cmd64x always probes > before pmac due to the above hardwired device order in the kernel, 100% > reliable and deterministic. It's hardwired, and you have to patch the kernel > to change it. > > Here's a patch to the Linux kernel that changes the device probe order so the > kernel behaves like g3beige is expecting it to: > > --- a/drivers/ide/Makefile > +++ b/drivers/ide/Makefile > @@ -39,6 +39,7 @@ > obj-$(CONFIG_BLK_DEV_AMD74XX) += amd74xx.o > obj-$(CONFIG_BLK_DEV_ATIIXP) += atiixp.o > obj-$(CONFIG_BLK_DEV_CELLEB) += scc_pata.o > +obj-$(CONFIG_BLK_DEV_IDE_PMAC) += pmac.o > obj-$(CONFIG_BLK_DEV_CMD64X) += cmd64x.o > obj-$(CONFIG_BLK_DEV_CS5520) += cs5520.o > obj-$(CONFIG_BLK_DEV_CS5530) += cs5530.o > @@ -76,8 +77,6 @@ > > obj-$(CONFIG_BLK_DEV_CMD640) += cmd640.o > > -obj-$(CONFIG_BLK_DEV_IDE_PMAC) += pmac.o > - > obj-$(CONFIG_IDE_H8300) += ide-h8300.o > > obj-$(CONFIG_IDE_GENERIC) += ide-generic.o > > > The problem is, the kernel guys will never take that patch upstream because > what they're currently doing isn't actually wrong. Their behavior is > consistent, the kernel's been probing the same devices in the same order > since > the 90's, and they don't really care what order things go in. > > The problem is that the association between qemu's command line arguments and > the devices they refer to is somewhat arbitrary. On the other targets I've > used (arm, mips, x86, and so on), the device QEMU initializes in response to > "-hda" is the one the Linux kernel makes /dev/hda (or /dev/sda), and the one > it intializes in response to "-hdc" is the one Linux makes /dev/hdc. But in > this case, they don't match up, and that's screwing up my same init/build > script that works fine on all the other tarets. > > Here's a patch to QEMU that makes those arguments intialize the devices the > kernel expects them to. This doesn't change where any of the hardware is on > the board, just which command line arguments associate with which drives:
This is wrong. On my OpenSUSE 11.1 guest the devices come up in correct order. They also do so on Aurelien's Debian images (IIRC). I guess it mostly works fine when using modules instead of compiled in drivers. Please find a real G3 beige and see what's different on it. I'd bet the real difference is that all 4 devices are attached to MacIO. But from what I remember DBDMA with cd-roms wasn't considered stable, hence the use of cmd64x on the second channel. Alex
