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| author | Tejun Heo <htejun@gmail.com> | 2007-09-23 13:14:12 +0900 |
|---|---|---|
| committer | Jeff Garzik <jeff@garzik.org> | 2007-10-12 14:55:41 -0400 |
| commit | 31cc23b34913bc173680bdc87af79e551bf8cc0d (patch) | |
| tree | ec64421ead9259174f0de8b22c36449ece6d69a4 /drivers/ata/sata_sil24.c | |
| parent | fb7fd61454c8681cd2621051a710b78a00369203 (diff) | |
| download | linux-31cc23b34913bc173680bdc87af79e551bf8cc0d.tar.bz2 | |
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_sil24.c')
| -rw-r--r-- | drivers/ata/sata_sil24.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/drivers/ata/sata_sil24.c b/drivers/ata/sata_sil24.c index d9c010ab2280..9acfce43bde4 100644 --- a/drivers/ata/sata_sil24.c +++ b/drivers/ata/sata_sil24.c @@ -393,6 +393,7 @@ static const struct ata_port_operations sil24_ops = { .tf_read = sil24_tf_read, + .qc_defer = ata_std_qc_defer, .qc_prep = sil24_qc_prep, .qc_issue = sil24_qc_issue, |