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;
}
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