mmc: mmci: add optional reset property

This patch adds a optional reset management.
STM32 sdmmc variant needs to reset hardware block
during the power cycle procedure (for re-initialization).
Signed-off-by: Ludovic Barre <ludovic.barre@st.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/mmci.c

@@ -36,6 +36,7 @@
 #include <linux/pm_runtime.h>
 #include <linux/types.h>
 #include <linux/pinctrl/consumer.h>
+#include <linux/reset.h>
 
 #include <asm/div64.h>
 #include <asm/io.h>
@@ -1882,6 +1883,12 @@ static int mmci_probe(struct amba_device *dev,
 
 	dev_dbg(mmc_dev(mmc), "clocking block at %u Hz\n", mmc->f_max);
 
+	host->rst = devm_reset_control_get_optional_exclusive(&dev->dev, NULL);
+	if (IS_ERR(host->rst)) {
+		ret = PTR_ERR(host->rst);
+		goto clk_disable;
+	}
+
 	/* Get regulators and the supported OCR mask */
 	ret = mmc_regulator_get_supply(mmc);
 	if (ret)

drivers/mmc/host/mmci.h

@@ -318,6 +318,8 @@ struct mmci_host {
 	struct clk		*clk;
 	u8			singleirq:1;
 
+	struct reset_control	*rst;
+
 	spinlock_t		lock;
 
 	unsigned int		mclk;