+static int ahci_stop_engine(struct ata_port *ap)
+{
+ void __iomem *mmio = ap->host_set->mmio_base;
+ void __iomem *port_mmio = ahci_port_base(mmio, ap->port_no);
+ int work;
+ u32 tmp;
+
+ tmp = readl(port_mmio + PORT_CMD);
+ tmp &= ~PORT_CMD_START;
+ writel(tmp, port_mmio + PORT_CMD);
+
+ /* wait for engine to stop. TODO: this could be
+ * as long as 500 msec
+ */
+ work = 1000;
+ while (work-- > 0) {
+ tmp = readl(port_mmio + PORT_CMD);
+ if ((tmp & PORT_CMD_LIST_ON) == 0)
+ return 0;
+ udelay(10);
+ }
+
+ return -EIO;
+}
+
+static void ahci_start_engine(struct ata_port *ap)
+{
+ void __iomem *mmio = ap->host_set->mmio_base;
+ void __iomem *port_mmio = ahci_port_base(mmio, ap->port_no);
+ u32 tmp;
+
+ tmp = readl(port_mmio + PORT_CMD);
+ tmp |= PORT_CMD_START;
+ writel(tmp, port_mmio + PORT_CMD);
+ readl(port_mmio + PORT_CMD); /* flush */
+}
+