Tejun Heo wrote:
Hello, Mark.
Mark Lord wrote:
Are there controllers which *can* handle such a mix (ahci, sil24 ?)
Yeap, sil24 can. ahci can currently only do device based switching but
ahci 2.0 can do it too.
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?
So, none of the others needs this.
This seems (below) to work for sata_mv. But I still wonder about
other LLDs.
..
Mmm.. Found another problem with sata_mv vs. the standard .qc_defer ops:
they don't prevent PIO commands from getting into the mix.
So now I have this in sata_mv, for all chip versions:
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;
/*
* If the port is completely idle, then allow the new qc.
*/
if (ap->nr_active_links == 0)
return 0;
/*
* If the port is not in host-queue mode (EDMA), then defer the new qc.
*/
pp = ap->private_data;
if (!(pp->pp_flags & MV_PP_FLAG_EDMA_EN))
return ATA_DEFER_PORT;
if (pp->pp_flags & MV_PP_FLAG_NCQ_EN) {
/*
* The host queue (EDMA) is in NCQ mode.
* If the new qc is also an NCQ command,
* then allow the new qc.
*/
if (qc->tf.protocol == ATA_PROT_NCQ)
return 0;
} else {
/*
* The host queue (EDMA) is in non-NCQ, DMA mode.
* If the new qc is also a non-NCQ, DMA command,
* then allow the new qc.
*/
if (qc->tf.protocol == ATA_PROT_DMA)
return 0;
}
return ATA_DEFER_PORT;
}
For the first time ever, I can now *heavily* mix PIO commands
with NCQ/non-NCQ DMA commands, to drives on an attached PM
(well, two attached PMs even), and the thing doesn't croak.
Woo-hoo!
Time to batch up some patches for Jeff. But sadly, just in time
to have missed his weekly visit to linux-ide. :)
I wonder if something like that is what bit sata_sil24 the other day
when I had it plugged in, mixing DMA, NCQ, and PIO commands to drives
on an attached PM?
Cheers
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