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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: Mark Lord <mlord@pobox.com> Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
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@ -888,6 +888,25 @@ static void mv_start_dma(struct ata_port *ap, void __iomem *port_mmio,
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}
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}
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static void mv_wait_for_edma_empty_idle(struct ata_port *ap)
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{
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void __iomem *port_mmio = mv_ap_base(ap);
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const u32 empty_idle = (EDMA_STATUS_CACHE_EMPTY | EDMA_STATUS_IDLE);
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const int per_loop = 5, timeout = (15 * 1000 / per_loop);
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int i;
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/*
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* Wait for the EDMA engine to finish transactions in progress.
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*/
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for (i = 0; i < timeout; ++i) {
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u32 edma_stat = readl(port_mmio + EDMA_STATUS_OFS);
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if ((edma_stat & empty_idle) == empty_idle)
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break;
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udelay(per_loop);
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}
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/* ata_port_printk(ap, KERN_INFO, "%s: %u+ usecs\n", __func__, i); */
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}
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/**
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* mv_stop_edma_engine - Disable eDMA engine
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* @port_mmio: io base address
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@ -920,6 +939,7 @@ static int mv_stop_edma(struct ata_port *ap)
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if (!(pp->pp_flags & MV_PP_FLAG_EDMA_EN))
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return 0;
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pp->pp_flags &= ~MV_PP_FLAG_EDMA_EN;
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mv_wait_for_edma_empty_idle(ap);
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if (mv_stop_edma_engine(port_mmio)) {
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ata_port_printk(ap, KERN_ERR, "Unable to stop eDMA\n");
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return -EIO;
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