From 31cc23b34913bc173680bdc87af79e551bf8cc0d Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Sun, 23 Sep 2007 13:14:12 +0900 Subject: 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 Signed-off-by: Jeff Garzik --- drivers/ata/sata_sil24.c | 1 + 1 file changed, 1 insertion(+) (limited to 'drivers/ata/sata_sil24.c') 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, -- cgit v1.2.3