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| author | Tejun Heo <htejun@gmail.com> | 2007-09-23 06:14:12 +0200 |
|---|---|---|
| committer | Jeff Garzik <jeff@garzik.org> | 2007-10-12 20:55:41 +0200 |
| commit | 31cc23b34913bc173680bdc87af79e551bf8cc0d (patch) | |
| tree | ec64421ead9259174f0de8b22c36449ece6d69a4 /drivers/ata/sata_nv.c | |
| parent | libata-pmp-prep: make a number of functions global to libata (diff) | |
| download | linux-31cc23b34913bc173680bdc87af79e551bf8cc0d.tar.xz linux-31cc23b34913bc173680bdc87af79e551bf8cc0d.zip | |
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.c | 1 |
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 = { .bmdma_start = ata_bmdma_start, .bmdma_stop = ata_bmdma_stop, .bmdma_status = ata_bmdma_status, + .qc_defer = ata_std_qc_defer, .qc_prep = nv_adma_qc_prep, .qc_issue = nv_adma_qc_issue, .freeze = nv_adma_freeze, |