Re: Regression between v3.5 and v3.6 in libata

[Aaron Lu <aaron.lwe@gmail.com>]

On 02/27/2013 05:38 PM, Jan Sembera wrote:
> On Wed, Feb 27, 2013 at 12:36:07AM -0600, Robert Hancock wrote:
>> On 02/26/2013 04:07 PM, Jan Sembera wrote:
>>> So I apparently missed two most important differences between good and bad
>>> boots.
>>>
>>> On Tue, Feb 26, 2013 at 09:03:48PM +0100, Jan Sembera wrote:
>>>> [    2.877438] scsi6 : pata_atiixp
>>>> [    2.881369] scsi7 : pata_atiixp
>>>>
>>>> [    2.391535] scsi6 : pata_acpi
>>>> [    2.391994] scsi7 : pata_acpi
>>>
>>> pata-acpi doesn't play very well with this controller. Disabling it in
>>> kernel and rebooting (even with 3.8) provided completely working kernel.
>>> So either this driver shouldn't bind pata-acpi and leave it on pata-atiixp
>>> as before (some kind of blacklisting needed?), or it needs some fixing to
>>> work nicely with this controller.
>>>
>>> As a workaround for now, I'll just not compile PATA_ACPI into the kernel.
>>
>> What are your kernel config settings for these modules? The idea is that
>> pata_acpi is only supposed to get loaded if no other driver is able to
>> bind to the device.
>
> This is based on a config that Ubuntu uses for building vanilla kernels and
> has PATA_ACPI=y, PATA_ATIIXP=m. Which probably means that pata_acpi will
> grab the controller before pata_atiixp has any chance to do so. Which is
> probably bad and should be set to PATA_ACPI=m instead.
>
> Should this also be treated as a bug in pata_acpi, or is it expected that
> it's going to fail on some subset of motherboards/controllers and it's not
> worth bothering with fixing it, especially if there is some other driver
> that handles the controller fine?

The order here is important: vendor driver should always be used before
pata_acpi.

And regarding the bisected commit, it actually fixed a bug in pata_acpi
and made it successfully probed the controller device, so that no other
pata driver is able to probe it; and due to pata_acpi can not always
successfully drive that controller(this depends on ACPI table, it may
not be a bug in pata_acpi), the disks attached will not function
properly. Here is an explanation on this:
https://bugzilla.kernel.org/show_bug.cgi?id=49151#c41

And a previously submitted bug report on this:
https://bugzilla.kernel.org/show_bug.cgi?id=48631

Thanks,
Aaron