pmic: add stpmu1 support

This driver implements register read/write operations for STPMU1.

The STPMU1 PMIC provides 4 BUCKs, 6 LDOs, 1 VREF
and 2 power switches. It is accessed via an I2C interface.
This device is used with STM32MP1 SoCs.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/drivers/power/pmic/stpmu1.c b/drivers/power/pmic/stpmu1.c
new file mode 100644
index 0000000..4615365
--- /dev/null
+++ b/drivers/power/pmic/stpmu1.c
@@ -0,0 +1,62 @@
+/*
+ * Copyright (C) 2018, STMicroelectronics - All Rights Reserved
+ *
+ * SPDX-License-Identifier:	GPL-2.0+	BSD-3-Clause
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <errno.h>
+#include <i2c.h>
+#include <power/pmic.h>
+#include <power/stpmu1.h>
+
+#define STMPU1_NUM_OF_REGS 0x100
+
+static int stpmu1_reg_count(struct udevice *dev)
+{
+	return STMPU1_NUM_OF_REGS;
+}
+
+static int stpmu1_write(struct udevice *dev, uint reg, const uint8_t *buff,
+			int len)
+{
+	int ret;
+
+	ret = dm_i2c_write(dev, reg, buff, len);
+	if (ret)
+		dev_err(dev, "%s: failed to write register %#x :%d",
+			__func__, reg, ret);
+
+	return ret;
+}
+
+static int stpmu1_read(struct udevice *dev, uint reg, uint8_t *buff, int len)
+{
+	int ret;
+
+	ret = dm_i2c_read(dev, reg, buff, len);
+	if (ret)
+		dev_err(dev, "%s: failed to read register %#x : %d",
+			__func__, reg, ret);
+
+	return ret;
+}
+
+static struct dm_pmic_ops stpmu1_ops = {
+	.reg_count = stpmu1_reg_count,
+	.read = stpmu1_read,
+	.write = stpmu1_write,
+};
+
+static const struct udevice_id stpmu1_ids[] = {
+	{ .compatible = "st,stpmu1" },
+	{ }
+};
+
+U_BOOT_DRIVER(pmic_stpmu1) = {
+	.name = "stpmu1_pmic",
+	.id = UCLASS_PMIC,
+	.of_match = stpmu1_ids,
+	.ops = &stpmu1_ops,
+};