nvme: Respect timeout when en/disabling the controller

So far the driver unconditionally delays 10ms when en/disabling the
controller and still return 0 if 10ms times out. In fact, spec defines
a timeout value in the CAP register that is the worst case time that
host software shall wait for the controller to become ready.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>

drivers/nvme/nvme.c

@@ -47,11 +47,19 @@ struct nvme_queue {
 static int nvme_wait_ready(struct nvme_dev *dev, bool enabled)
 {
 	u32 bit = enabled ? NVME_CSTS_RDY : 0;
+	int timeout;
+	ulong start;
 
-	while ((readl(&dev->bar->csts) & NVME_CSTS_RDY) != bit)
-		udelay(10000);
+	/* Timeout field in the CAP register is in 500 millisecond units */
+	timeout = NVME_CAP_TIMEOUT(dev->cap) * 500;
 
-	return 0;
+	start = get_timer(0);
+	while (get_timer(start) < timeout) {
+		if ((readl(&dev->bar->csts) & NVME_CSTS_RDY) == bit)
+			return 0;
+	}
+
+	return -ETIME;
 }
 
 static int nvme_setup_prps(struct nvme_dev *dev, u64 *prp2,