wl1271: Add pre-power-on sleep

This patch adds a short delay before powering on the wl1271. Normally, it is
not needed, but if the wl1271 has been powered off shortly before, for reliable
firmware-booting this small stabilization delay is required.

Signed-off-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Reviewed-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/wl12xx/wl1271.h

@@ -458,7 +458,9 @@ int wl1271_plt_stop(struct wl1271 *wl);
 
 #define WL1271_TX_QUEUE_MAX_LENGTH 20
 
-/* WL1271 needs a 200ms sleep after power on */
+/* WL1271 needs a 200ms sleep after power on, and a 20ms sleep before power
+   on in case is has been shut down shortly before */
+#define WL1271_PRE_POWER_ON_SLEEP 20 /* in miliseconds */
 #define WL1271_POWER_ON_SLEEP 200 /* in miliseconds */
 
 static inline bool wl1271_11a_enabled(void)

drivers/net/wireless/wl12xx/wl1271_main.c

@@ -618,6 +618,7 @@ static int wl1271_chip_wakeup(struct wl1271 *wl)
 	struct wl1271_partition_set partition;
 	int ret = 0;
 
+	msleep(WL1271_PRE_POWER_ON_SLEEP);
 	wl1271_power_on(wl);
 	msleep(WL1271_POWER_ON_SLEEP);
 	wl1271_spi_reset(wl);