[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] qemu-system-ppc -m g3beige -hda is setting /dev/hdc on
Re: [Qemu-devel] qemu-system-ppc -m g3beige -hda is setting /dev/hdc on Linux.
Sat, 13 Feb 2010 11:28:44 +0100
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
> 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
> 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
> 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.