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sata_mv wait for empty+idle

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When performing EH, it is recommended to wait for the EDMA engine
to empty out requests-in-progress before disabling EDMA.

Introduce code to poll the EDMA_STATUS register for idle/empty bits
before disabling EDMA.  For non-EH operation, this will normally exit
without delay, other than the register read.

A later series of patches may focus on eliminating this and various
other register reads (when possible) throughout the driver,
but for now we're focussing on solid reliablity.

Signed-off-by: Mark Lord <mlord@pobox.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
This commit is contained in:
Mark Lord 2008-05-02 02:09:14 -04:00 committed by Jeff Garzik
parent 616d4a98ad
commit 9b2c4e0bae
1 changed files with 20 additions and 0 deletions
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20
drivers/ata/sata_mv.c
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@ -888,6 +888,25 @@ static void mv_start_dma(struct ata_port *ap, void __iomem *port_mmio,
}
}
static void mv_wait_for_edma_empty_idle(struct ata_port *ap)
{
void __iomem *port_mmio = mv_ap_base(ap);
const u32 empty_idle = (EDMA_STATUS_CACHE_EMPTY | EDMA_STATUS_IDLE);
const int per_loop = 5, timeout = (15 * 1000 / per_loop);
int i;
/*
* Wait for the EDMA engine to finish transactions in progress.
*/
for (i = 0; i < timeout; ++i) {
u32 edma_stat = readl(port_mmio + EDMA_STATUS_OFS);
if ((edma_stat & empty_idle) == empty_idle)
break;
udelay(per_loop);
}
/* ata_port_printk(ap, KERN_INFO, "%s: %u+ usecs\n", __func__, i); */
}
/**
* mv_stop_edma_engine - Disable eDMA engine
* @port_mmio: io base address
@ -920,6 +939,7 @@ static int mv_stop_edma(struct ata_port *ap)
if (!(pp->pp_flags & MV_PP_FLAG_EDMA_EN))
return 0;
pp->pp_flags &= ~MV_PP_FLAG_EDMA_EN;
mv_wait_for_edma_empty_idle(ap);
if (mv_stop_edma_engine(port_mmio)) {
ata_port_printk(ap, KERN_ERR, "Unable to stop eDMA\n");
return -EIO;