Re: [PATCH] libata: always use polling SETXFER

[Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>]

On Wednesday 14 March 2007, Tejun Heo wrote:
> Several people have reported LITE-ON LTR-48246S detection failed
> because SETXFER fails.  It seems the device raises IRQ too early after
> SETXFER.  This is controller independent.  The same problem has been
> reported for different controllers.
> 
> So, now we have pata_via where the controller raises IRQ before it's
> ready after SETXFER and a device which does similar thing.  This patch
> makes libata always execute SETXFER via polling.  As this only happens
> during EH, performance impact is nil.  Setting ATA_TFLAG_POLLING is
> also moved from issue hot path to ata_dev_set_xfermode() - the only
> place where SETXFER can be issued.
> 
> Jeff Garzik suggests that, in the long term, it might be better to
> modify libata HSM implementation such that we're more tolerant of
> erratic ATAPI IRQ behavior - e.g. default to IRQ but falling back to
> polling if the device doesn't seem ready at the point of interrupt.
> Such change might be necessary to support ancient/weird ATAPI devices.
> 
> Signed-off-by: Tejun Heo <htejun@gmail.com>

Acked-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>