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authorTejun Heo <htejun@gmail.com>2007-09-23 00:14:12 -0400
committerJeff Garzik <jeff@garzik.org>2007-10-12 14:55:41 -0400
commit31cc23b34913bc173680bdc87af79e551bf8cc0d (patch)
treeec64421ead9259174f0de8b22c36449ece6d69a4 /drivers/ata/sata_nv.c
parentfb7fd61454c8681cd2621051a710b78a00369203 (diff)
libata-pmp-prep: implement ops->qc_defer()
Controllers which support PMP have various restrictions on which combinations of commands are allowed to what number of devices concurrently. This patch implements ops->qc_defer() which determines whether a qc can be issued at the moment or should be deferred. If the function returns ATA_DEFER_LINK, the qc will be deferred until a qc completes on the link. If ATA_DEFER_PORT, until a qc completes on any link. The defer conditions are advisory and in general ATA_DEFER_LINK can be considered as lower priority deferring than ATA_DEFER_PORT. ops->qc_defer() replaces fixed ata_scmd_need_defer(). For standard NCQ/non-NCQ exclusion, ata_std_qc_defer() is implemented. ahci and sata_sil24 are converted to use ata_std_qc_defer(). ops->qc_defer() is heavier than the original mechanism because full qc is prepped before determining to defer it, but various information is needed to determine defer conditinos and fully translating a qc is the only way to supply such information in generic manner. IMHO, this shouldn't cause any noticeable performance issues as * for most cases deferring occurs rarely (except for NCQ-aware cmd-switching PMP) * translation itself isn't that expensive * once deferred the command won't be repeated until another command completes which usually is a very long time cpu-wise. Signed-off-by: Tejun Heo <htejun@gmail.com> Signed-off-by: Jeff Garzik <jeff@garzik.org>
Diffstat (limited to 'drivers/ata/sata_nv.c')
-rw-r--r--drivers/ata/sata_nv.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/drivers/ata/sata_nv.c b/drivers/ata/sata_nv.c
index b860f99fc288..40557fe2ffdf 100644
--- a/drivers/ata/sata_nv.c
+++ b/drivers/ata/sata_nv.c
@@ -423,6 +423,7 @@ static const struct ata_port_operations nv_adma_ops = {
423 .bmdma_start = ata_bmdma_start, 423 .bmdma_start = ata_bmdma_start,
424 .bmdma_stop = ata_bmdma_stop, 424 .bmdma_stop = ata_bmdma_stop,
425 .bmdma_status = ata_bmdma_status, 425 .bmdma_status = ata_bmdma_status,
426 .qc_defer = ata_std_qc_defer,
426 .qc_prep = nv_adma_qc_prep, 427 .qc_prep = nv_adma_qc_prep,
427 .qc_issue = nv_adma_qc_issue, 428 .qc_issue = nv_adma_qc_issue,
428 .freeze = nv_adma_freeze, 429 .freeze = nv_adma_freeze,