mmc: tmio: fix unbalanced power-on calls with clock-gating enabled

With MMC clock gating enabled the MMC core currently calls MMC host driver's
.set_ios() method with .power_mode == MMC_POWER_ON and the clock value set
either to 0 or to the target rate. The tmio MMC driver then wrongly
translates the latter calls to card slot power-on requests, even when the
slot already was on. This patch fixes the driver to avoid needlessly
incrementing power-supplying regulator's use count.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski+renesas@gmail.com>
Tested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/host/tmio_mmc.h

@@ -40,6 +40,22 @@
 
 struct tmio_mmc_data;
 
+/*
+ * We differentiate between the following 3 power states:
+ * 1. card slot powered off, controller stopped. This is used, when either there
+ *    is no card in the slot, or the card really has to be powered down.
+ * 2. card slot powered on, controller stopped. This is used, when a card is in
+ *    the slot, but no activity is currently taking place. This is a power-
+ *    saving mode with card-state preserved. This state can be entered, e.g.
+ *    when MMC clock-gating is used.
+ * 3. card slot powered on, controller running. This is the actual active state.
+ */
+enum tmio_mmc_power {
+	TMIO_MMC_OFF_STOP,	/* card power off, controller stopped */
+	TMIO_MMC_ON_STOP,	/* card power on, controller stopped */
+	TMIO_MMC_ON_RUN,	/* card power on, controller running */
+};
+
 struct tmio_mmc_host {
 	void __iomem *ctl;
 	unsigned long bus_shift;
@@ -48,8 +64,8 @@ struct tmio_mmc_host {
 	struct mmc_data         *data;
 	struct mmc_host         *mmc;
 
-	/* Controller power state */
-	bool			power;
+	/* Controller and card power state */
+	enum tmio_mmc_power	power;
 
 	/* Callbacks for clock / power control */
 	void (*set_pwr)(struct platform_device *host, int state);