[PATCH 4/7] reset: add reset controller driver for STM32 RCC

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

On the STM32MP, reset of the I2C, SPI and USB IPs occurs over the RCC.
This driver adds support for the controller, so it may be reused by
other drivers.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 drivers/reset/Kconfig       |   5 ++
 drivers/reset/Makefile      |   1 +
 drivers/reset/reset-stm32.c | 109 ++++++++++++++++++++++++++++++++++++
 3 files changed, 115 insertions(+)
 create mode 100644 drivers/reset/reset-stm32.c

diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
index caf1dc9acb44..048f2081f82a 100644
--- a/drivers/reset/Kconfig
+++ b/drivers/reset/Kconfig
@@ -21,4 +21,9 @@ config RESET_IMX7
 	help
 	  This enables the reset controller driver for i.MX7 SoCs.
 
+config RESET_STM32
+	bool "STM32 Reset Driver"
+	help
+	  This enables the reset controller driver for STM32MP and STM32 MCUs.
+
 endif
diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
index 0b55caa20445..8460c4b154f5 100644
--- a/drivers/reset/Makefile
+++ b/drivers/reset/Makefile
@@ -1,3 +1,4 @@
 obj-$(CONFIG_RESET_CONTROLLER) += core.o
 obj-$(CONFIG_ARCH_SOCFPGA) += reset-socfpga.o
 obj-$(CONFIG_RESET_IMX7) += reset-imx7.o
+obj-$(CONFIG_RESET_STM32) += reset-stm32.o
diff --git a/drivers/reset/reset-stm32.c b/drivers/reset/reset-stm32.c
new file mode 100644
index 000000000000..ff66fe310e1a
--- /dev/null
+++ b/drivers/reset/reset-stm32.c
@@ -0,0 +1,109 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2017, STMicroelectronics - All Rights Reserved
+ * Copyright (C) 2019, Ahmad Fatoum, Pengutronix
+ * Author(s): Patrice Chotard, <patrice.chotard@st.com> for STMicroelectronics.
+ */
+
+#include <common.h>
+#include <init.h>
+#include <linux/err.h>
+#include <linux/reset-controller.h>
+#include <asm/io.h>
+
+#define RCC_CL 0x4
+
+struct stm32_reset {
+	void __iomem *base;
+	struct reset_controller_dev rcdev;
+	void (*reset)(void __iomem *reg, unsigned offset, bool assert);
+};
+
+static struct stm32_reset *to_stm32_reset(struct reset_controller_dev *rcdev)
+{
+	return container_of(rcdev, struct stm32_reset, rcdev);
+}
+
+static void stm32mp_reset(void __iomem *reg, unsigned offset, bool assert)
+{
+	if (assert)
+		offset += RCC_CL;
+
+	writel(BIT(offset), reg);
+}
+
+static void stm32mcu_reset(void __iomem *reg, unsigned offset, bool assert)
+{
+	if (assert)
+		setbits_le32(reg, BIT(offset));
+	else
+		clrbits_le32(reg, BIT(offset));
+}
+
+static void stm32_reset(struct stm32_reset *priv, unsigned long id, bool assert)
+{
+	int bank = (id / BITS_PER_LONG) * 4;
+	int offset = id % BITS_PER_LONG;
+
+	priv->reset(priv->base + bank, offset, assert);
+}
+
+static int stm32_reset_assert(struct reset_controller_dev *rcdev,
+			      unsigned long id)
+{
+	stm32_reset(to_stm32_reset(rcdev), id, true);
+	return 0;
+}
+
+static int stm32_reset_deassert(struct reset_controller_dev *rcdev,
+				unsigned long id)
+{
+	stm32_reset(to_stm32_reset(rcdev), id, false);
+	return 0;
+}
+
+static const struct reset_control_ops stm32_reset_ops = {
+	.assert		= stm32_reset_assert,
+	.deassert	= stm32_reset_deassert,
+};
+
+static int stm32_reset_probe(struct device_d *dev)
+{
+	struct stm32_reset *priv;
+	struct resource *iores;
+	int ret;
+
+	priv = xzalloc(sizeof(*priv));
+	ret = dev_get_drvdata(dev, (const void **)&priv->reset);
+	if (ret)
+		return ret;
+
+	iores = dev_request_mem_resource(dev, 0);
+	if (IS_ERR(iores))
+		return PTR_ERR(iores);
+
+	priv->base = IOMEM(iores->start);
+	priv->rcdev.nr_resets = (iores->end - iores->start) * BITS_PER_BYTE;
+	priv->rcdev.ops = &stm32_reset_ops;
+	priv->rcdev.of_node = dev->device_node;
+
+	return reset_controller_register(&priv->rcdev);
+}
+
+static const struct of_device_id stm32_rcc_reset_dt_ids[] = {
+	{ .compatible = "st,stm32mp1-rcc", .data = stm32mp_reset },
+	{ .compatible = "st,stm32-rcc", .data = stm32mcu_reset },
+	{ /* sentinel */ },
+};
+
+static struct driver_d stm32_rcc_reset_driver = {
+	.name = "stm32_rcc_reset",
+	.probe = stm32_reset_probe,
+	.of_compatible = DRV_OF_COMPAT(stm32_rcc_reset_dt_ids),
+};
+
+static int stm32_rcc_reset_init(void)
+{
+	return platform_driver_register(&stm32_rcc_reset_driver);
+}
+postcore_initcall(stm32_rcc_reset_init);
-- 
2.20.1


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