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/libata-core.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) (limited to 'drivers/ata/libata-core.c') diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c index 9467c2f6019..b666f51da7e 100644 --- a/drivers/ata/libata-core.c +++ b/drivers/ata/libata-core.c @@ -4345,6 +4345,36 @@ int ata_check_atapi_dma(struct ata_queued_cmd *qc) return 0; } +/** + * ata_std_qc_defer - Check whether a qc needs to be deferred + * @qc: ATA command in question + * + * Non-NCQ commands cannot run with any other command, NCQ or + * not. As upper layer only knows the queue depth, we are + * responsible for maintaining exclusion. This function checks + * whether a new command @qc can be issued. + * + * LOCKING: + * spin_lock_irqsave(host lock) + * + * RETURNS: + * ATA_DEFER_* if deferring is needed, 0 otherwise. + */ +int ata_std_qc_defer(struct ata_queued_cmd *qc) +{ + struct ata_link *link = qc->dev->link; + + if (qc->tf.protocol == ATA_PROT_NCQ) { + if (!ata_tag_valid(link->active_tag)) + return 0; + } else { + if (!ata_tag_valid(link->active_tag) && !link->sactive) + return 0; + } + + return ATA_DEFER_LINK; +} + /** * ata_qc_prep - Prepare taskfile for submission * @qc: Metadata associated with taskfile to be prepared @@ -7111,6 +7141,7 @@ EXPORT_SYMBOL_GPL(ata_interrupt); EXPORT_SYMBOL_GPL(ata_do_set_mode); EXPORT_SYMBOL_GPL(ata_data_xfer); EXPORT_SYMBOL_GPL(ata_data_xfer_noirq); +EXPORT_SYMBOL_GPL(ata_std_qc_defer); EXPORT_SYMBOL_GPL(ata_qc_prep); EXPORT_SYMBOL_GPL(ata_dumb_qc_prep); EXPORT_SYMBOL_GPL(ata_noop_qc_prep); -- cgit v1.2.3