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@xxxxxxxxx>
--- old/drivers/ata/sata_mv.c 2009-01-16 11:52:17.000000000 -0500
+++ linux/drivers/ata/sata_mv.c 2009-01-19 16:47:24.000000000 -0500
@@ -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 @@
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 @@
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);
--
To unsubscribe from this list: send the line "unsubscribe linux-ide" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
