Re: patch "libata-sff: Fix oops for pnp devices with no ctl" causes regression

[Jeff Garzik <jeff@garzik.org>]

Alan Cox wrote:
>> And when booting with the commit applied, I instead get a whole lot of
>> messages like this (this is the first one, copied by hand):
>>
>> ata2.00: exception Emask 0x0 SAct 0x0 Serr 0x10000000 action 0x6 frozen
>> ata2: SError: { }
>> ata2.00: cmd c8/00:02:42:08:20/00:00:00:00:00/e0 tag 0 dma 1024 in
>>          res 40/00:00:00:00:00/00:00:00:00:00/00 Emask 0x4 (timeout)
>> ata2.00: status: { DRDY }
>> ata2: hard resetting link
>> ata2: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
>> ata2.00: configured for UDMA/133
>> ata2: EH complete
> 
> Well I've been over the patch twice now and I cannot see a single point
> at which the sequence of code that *should* be executed is any different.
> 
> Stick wmb();rmb(); (or similar barriers to compiler optimisation and I/O
> fencing) at the start and end of your ata_sff_altstatus() and see what
> happens, if it suddenly decides to behave or forcing it no inline makes
> it behave then that would be useful info.

If he's getting a timeout, I wonder if that points to
ata_sff_irq_status() ...