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

[Alan Cox <alan@lxorguk.ukuu.org.uk>]

> 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.