Re: [PATCH 2.6.25-rc6] sata_promise: fix hardreset hotplug events, take 2

[Tejun Heo <htejun@gmail.com>]

Mikael Pettersson wrote:
> A Promise SATA controller will signal hotplug events when a hard
> reset (COMRESET) is done on a port. These events aren't masked by
> the driver, and the unexpected interrupts will cause a sequence
> of failed reset attempts util libata's EH finally gives up.
> 
> This has not been a common problem so far, but the pending libata
> hardreset-by-default changes makes it a critical issue.
> 
> The solution is to disable hotplug events before a reset, and to
> reenable them afterwards. (Promise's driver does this too.)
> 
> This patch adds SATA-specific versions of ->freeze() and ->thaw()
> that also disable and enable hotplug events. PATA ports continue
> to use the old versions of ->freeze() and ->thaw().
> 
> Accesses to the hotplug register must be serialised via host->lock.
> We rely on ap->lock == &ap->host->lock and that libata takes this
> lock before ->freeze() and ->thaw(). Document this requirement.
> The interrupt handler is adjusted so its hotplug register accesses
> are inside the region protected by host->lock.
> 
> Tested on various chips (SATA300TX4, SATA300TX2plus, SATAII150TX4,
> FastTrack TX4000) with various combinations of SATA and PATA disks,
> with and without the pending hardreset-by-default changes.
> 
> Signed-off-by: Mikael Pettersson <mikpe@it.uu.se>

Acked-by: Tejun Heo <htejun@gmail.com>

Jeff, do you want to merge this first?  If so, I'll update the
prefer-hardreset and cleanup-sht-ops patchsets; otherwise, I'll massage
this patch a bit so that it fits on top of those two patchsets.

-- 
tejun