The following commit has been merged in the linux branch: commit 159a7ff7a13f9a02c75006f40c0561a3a81aefcd Author: Gwendal Grignou gwendal@google.com Date: Mon Oct 12 15:44:00 2009 -0700

sata_mv: Prevent PIO commands to be defered too long if traffic in progress.

Use excl_link when non NCQ commands are defered, to be sure they are processed as soon as outstanding commands are completed. It prevents some commands to be defered indifinitely when using a port multiplier.

Signed-off-by: Gwendal Grignou gwendal@google.com Signed-off-by: Jeff Garzik jgarzik@redhat.com

diff --git a/drivers/ata/sata_mv.c b/drivers/ata/sata_mv.c index 17f9ff9..6f5093b 100644 --- a/drivers/ata/sata_mv.c +++ b/drivers/ata/sata_mv.c @@ -1382,6 +1382,25 @@ static int mv_qc_defer(struct ata_queued_cmd *qc) */ if (pp->pp_flags & MV_PP_FLAG_DELAYED_EH) return ATA_DEFER_PORT; + + /* PIO commands need exclusive link: no other commands [DMA or PIO] + * can run concurrently. + * set excl_link when we want to send a PIO command in DMA mode + * or a non-NCQ command in NCQ mode. + * When we receive a command from that link, and there are no + * outstanding commands, mark a flag to clear excl_link and let + * the command go through. + */ + if (unlikely(ap->excl_link)) { + if (link == ap->excl_link) { + if (ap->nr_active_links) + return ATA_DEFER_PORT; + qc->flags |= ATA_QCFLAG_CLEAR_EXCL; + return 0; + } else + return ATA_DEFER_PORT; + } + /* * If the port is completely idle, then allow the new qc. */ @@ -1395,8 +1414,14 @@ static int mv_qc_defer(struct ata_queued_cmd *qc) * doesn't allow it. */ if ((pp->pp_flags & MV_PP_FLAG_EDMA_EN) && - (pp->pp_flags & MV_PP_FLAG_NCQ_EN) && ata_is_ncq(qc->tf.protocol)) - return 0; + (pp->pp_flags & MV_PP_FLAG_NCQ_EN)) { + if (ata_is_ncq(qc->tf.protocol)) + return 0; + else { + ap->excl_link = link; + return ATA_DEFER_PORT; + } + }

return ATA_DEFER_PORT; }