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Commit 9b2c4e0b authored by Mark Lord's avatar Mark Lord Committed by Jeff Garzik
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sata_mv wait for empty+idle 



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: default avatarMark Lord <mlord@pobox.com>
Signed-off-by: default avatarJeff Garzik <jgarzik@redhat.com>
parent 616d4a98

drivers/ata/sata_mv.c

+20 −0
Original line number Diff line number Diff line
@@ -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;