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@xxxxxxxxx>
--- old/drivers/ata/sata_mv.c 2008-05-01 17:49:53.000000000 -0400
+++ linux/drivers/ata/sata_mv.c 2008-05-01 17:56:54.000000000 -0400
@@ -888,6 +888,25 @@
}
}
+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 @@
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;
--
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