Re: ata_std_qc_defer not good enough for FIS-based switching ?

[Mark Lord <liml@rtr.ca>]

Mark Lord wrote:
> Tejun,
> 
> I've been trying to track down interrupt timeouts here with sata_mv,
> and I think I've found the problem
> 
> With a Marvell 7042 chip and a port-multiplier, the driver selects
> .qc_defer = ata_std_qc_defer, which is supposed to be correct for 
> FIS-based switching.
> 
> But.. There is a mix of NCQ and non-NCQ drives plugged into that PM,
> and ata_std_qc_defer() seems happy to mix things up by issuing NCQ commands
> to some ports while simultaneously sending non-NCQ commands to other ports.
> 
> Needless to say, this confuses the heck out of the hardware,
> which cannot tolerate non-NCQ commands in FIS-based switching mode,
> or NCQ commands in non FIS-based switching mode.
> 
> Are there controllers which *can* handle such a mix (ahci, sil24 ?)
> 
> So it looks like a I need a .qc_defer() function which examines all links
> from the common host port for activity, and then asks for command deferral
> when the new command has a different protocol than those that are 
> outstanding.
> 
> Weird that none of the other LLDs need this.  Or do they?
..

This seems (below) to work for sata_mv.  But I still wonder about other LLDs.


static int mv_qc_defer (struct ata_queued_cmd *qc)
{
	struct ata_link *link = qc->dev->link;
	struct ata_port *ap = link->ap;
	struct mv_port_priv *pp;
	int port_is_using_ncq;

	if (ap->nr_active_links == 0)
		return 0;
	pp = ap->private_data;
	port_is_using_ncq = ((pp->pp_flags & MV_PP_FLAG_NCQ_EN) != 0);
	if (qc->tf.protocol == ATA_PROT_NCQ) {
		if (port_is_using_ncq)
			return ata_std_qc_defer(qc);
	} else {
		if (!port_is_using_ncq)
			return sata_pmp_qc_defer_cmd_switch(qc);
	}
	return ATA_DEFER_LINK;
}