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sata_mv: don't read hc_irq_cause 

Remove silly read-modify-write sequences when clearing interrupts
in hc_irq_cause.  This gets rid of unneeded MMIO reads, resulting in
a slight performance boost when switching between EDMA and non-EDMA
modes (eg. for cache flushes).

Signed-off-by: Mark Lord <mlord@pobox.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
This commit is contained in:
Mark Lord 2009-01-19 18:05:42 -05:00 committed by Jeff Garzik
parent b0bccb18bc
commit cae6edc3b5
1 changed files with 5 additions and 12 deletions
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17
drivers/ata/sata_mv.c
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@ -35,8 +35,6 @@
*
* --> Investigate problems with PCI Message Signalled Interrupts (MSI).
*
* --> Cache frequently-accessed registers in mv_port_priv to reduce overhead.
*
* --> Develop a low-power-consumption strategy, and implement it.
*
* --> [Experiment, low priority] Investigate interrupt coalescing.
@ -884,18 +882,14 @@ static void mv_start_dma(struct ata_port *ap, void __iomem *port_mmio,
int hardport = mv_hardport_from_port(ap->port_no);
void __iomem *hc_mmio = mv_hc_base_from_port(
mv_host_base(ap->host), ap->port_no);
u32 hc_irq_cause, ipending;
u32 hc_irq_cause;
/* clear EDMA event indicators, if any */
writelfl(0, port_mmio + EDMA_ERR_IRQ_CAUSE_OFS);
/* clear EDMA interrupt indicator, if any */
hc_irq_cause = readl(hc_mmio + HC_IRQ_CAUSE_OFS);
ipending = (DEV_IRQ | DMA_IRQ) << hardport;
if (hc_irq_cause & ipending) {
writelfl(hc_irq_cause & ~ipending,
hc_mmio + HC_IRQ_CAUSE_OFS);
}
/* clear pending irq events */
hc_irq_cause = ~((DEV_IRQ | DMA_IRQ) << hardport);
writelfl(hc_irq_cause, hc_mmio + HC_IRQ_CAUSE_OFS);
mv_edma_cfg(ap, want_ncq);
@ -2821,8 +2815,7 @@ static void mv_eh_thaw(struct ata_port *ap)
writel(0, port_mmio + EDMA_ERR_IRQ_CAUSE_OFS);
/* clear pending irq events */
hc_irq_cause = readl(hc_mmio + HC_IRQ_CAUSE_OFS);
hc_irq_cause &= ~((DEV_IRQ | DMA_IRQ) << hardport);
hc_irq_cause = ~((DEV_IRQ | DMA_IRQ) << hardport);
writelfl(hc_irq_cause, hc_mmio + HC_IRQ_CAUSE_OFS);
mv_enable_port_irqs(ap, ERR_IRQ);