mmc: Wait for card_busy before starting sdio requests

Some sdio wifi chips will not work properly if we try to start new
sdio-rw requests while the device is signalling that it is busy.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/core/core.c

@@ -206,6 +206,23 @@ static void __mmc_start_request(struct mmc_host *host, struct mmc_request *mrq)
 		return;
 	}
 
+	/*
+	 * For sdio rw commands we must wait for card busy otherwise some
+	 * sdio devices won't work properly.
+	 */
+	if (mmc_is_io_op(mrq->cmd->opcode) && host->ops->card_busy) {
+		int tries = 500; /* Wait aprox 500ms at maximum */
+
+		while (host->ops->card_busy(host) && --tries)
+			mmc_delay(1);
+
+		if (tries == 0) {
+			mrq->cmd->error = -EBUSY;
+			mmc_request_done(host, mrq);
+			return;
+		}
+	}
+
 	host->ops->request(host, mrq);
 }