Re: Intel SATA combined mode quirk broken for SCSI_SATA=m

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Jesse Barnes wrote:
Back in July, Adrian Bunk sent in a patch to make SCSI_SATA tristate. This prevents the intel_ide_combined quirk in drivers/pci/quirks.c from working if SCSI_SATA=m, which is the case for Fedora kernels (my motivation for tracking this down).

In my configuration, not running the quirk causes the ata_piix driver (the libata driver for my IDE controller) to fail to attach to the device, since the legacy IDE driver has already claimed the ports. Unfortunately, the AHCI driver also tries to mess with the device, and ends up disabling its interrupts before aborting its load, causing the IDE layer to complain loudly that hda is losing interrupts.

Thanks a ton for figuring this out!


So what should be done? Ideally, libata would fully support ATAPI and then I wouldn't need the legacy IDE drivers at all on this box, making the quirk moot, but that won't happen for 2.6.14, so we'll need something else. Unconditionally enabling the quirk will cause at least one of the ports to be reserved for the SATA driver, which may never load. And obviously not running the quirk leads to the situation described above.

A hack that might be suitable for 2.6.14 is to make the quirk depend on either CONFIG_SCSI_SATA or CONFIG_SCSI_SATA_MODULE. Then the quirk could be removed entirely when ATAPI support for libata is merged.

Overall the quirk is a hack until ATAPI is supported -- but even after ATAPI is supported, we need to figure out some way to keep IDE driver from stealing the legacy IDE ports before libata can touch them :(

However, when ATAPI is supported, that at least means that both PATA and SATA can run at full speed.

Your patch is correct, and should go into 2.6.14-rc post-haste.

I continue to grumble at the Kconfig annoyance: CONFIG_SCSI_SATA is fundamentally a yes/no question. CONFIG_SCSI_SATA=m makes no sense at all -- and causes problems, as we see -- but is required in order to do Kconfig dependencies correctly AFAIK.

Maybe 'if SCSI_SATA' is needed instead? A lame way to implement dependencies, but if there is no other way...

	Jeff


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