[PATCH v4 09/16] reset: starfive-jh7100: Add StarFive JH7100 reset driver

[Emil Renner Berthing <kernel@xxxxxxxx>]

Add a driver for the StarFive JH7100 reset controller.

Signed-off-by: Emil Renner Berthing <kernel@xxxxxxxx>
---
 MAINTAINERS                           |   7 +
 drivers/reset/Kconfig                 |   7 +
 drivers/reset/Makefile                |   1 +
 drivers/reset/reset-starfive-jh7100.c | 176 ++++++++++++++++++++++++++
 4 files changed, 191 insertions(+)
 create mode 100644 drivers/reset/reset-starfive-jh7100.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 2548ef1f8246..1152f5d94690 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -18137,6 +18137,13 @@ F:	Documentation/devicetree/bindings/clock/starfive,jh7100-clkgen.yaml
 F:	drivers/clk/starfive/clk-starfive-jh7100.c
 F:	include/dt-bindings/clock/starfive-jh7100.h
 
+STARFIVE JH7100 RESET CONTROLLER DRIVER
+M:	Emil Renner Berthing <kernel@xxxxxxxx>
+S:	Maintained
+F:	Documentation/devicetree/bindings/reset/starfive,jh7100-reset.yaml
+F:	drivers/reset/reset-starfive-jh7100.c
+F:	include/dt-bindings/reset/starfive-jh7100.h
+
 STATIC BRANCH/CALL
 M:	Peter Zijlstra <peterz@xxxxxxxxxxxxx>
 M:	Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
index 85024eb1d2ea..6f8ba0ddc05f 100644
--- a/drivers/reset/Kconfig
+++ b/drivers/reset/Kconfig
@@ -224,6 +224,13 @@ config RESET_SOCFPGA
 	  This enables the reset driver for the SoCFPGA ARMv7 platforms. This
 	  driver gets initialized early during platform init calls.
 
+config RESET_STARFIVE_JH7100
+	bool "StarFive JH7100 Reset Driver"
+	depends on SOC_STARFIVE || COMPILE_TEST
+	default SOC_STARFIVE
+	help
+	  This enables the reset controller driver for the StarFive JH7100 SoC.
+
 config RESET_SUNXI
 	bool "Allwinner SoCs Reset Driver" if COMPILE_TEST && !ARCH_SUNXI
 	default ARCH_SUNXI
diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
index 21d46d8869ff..bd0a97be18b5 100644
--- a/drivers/reset/Makefile
+++ b/drivers/reset/Makefile
@@ -29,6 +29,7 @@ obj-$(CONFIG_RESET_RZG2L_USBPHY_CTRL) += reset-rzg2l-usbphy-ctrl.o
 obj-$(CONFIG_RESET_SCMI) += reset-scmi.o
 obj-$(CONFIG_RESET_SIMPLE) += reset-simple.o
 obj-$(CONFIG_RESET_SOCFPGA) += reset-socfpga.o
+obj-$(CONFIG_RESET_STARFIVE_JH7100) += reset-starfive-jh7100.o
 obj-$(CONFIG_RESET_SUNXI) += reset-sunxi.o
 obj-$(CONFIG_RESET_TI_SCI) += reset-ti-sci.o
 obj-$(CONFIG_RESET_TI_SYSCON) += reset-ti-syscon.o
diff --git a/drivers/reset/reset-starfive-jh7100.c b/drivers/reset/reset-starfive-jh7100.c
new file mode 100644
index 000000000000..2f7615cbf1dc
--- /dev/null
+++ b/drivers/reset/reset-starfive-jh7100.c
@@ -0,0 +1,176 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Reset driver for the StarFive JH7100 SoC
+ *
+ * Copyright (C) 2021 Emil Renner Berthing <kernel@xxxxxxxx>
+ */
+
+#include <linux/bitmap.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/mod_devicetable.h>
+#include <linux/platform_device.h>
+#include <linux/reset-controller.h>
+#include <linux/spinlock.h>
+
+#include <dt-bindings/reset/starfive-jh7100.h>
+
+/* register offsets */
+#define JH7100_RESET_ASSERT0	0x00
+#define JH7100_RESET_ASSERT1	0x04
+#define JH7100_RESET_ASSERT2	0x08
+#define JH7100_RESET_ASSERT3	0x0c
+#define JH7100_RESET_STATUS0	0x10
+#define JH7100_RESET_STATUS1	0x14
+#define JH7100_RESET_STATUS2	0x18
+#define JH7100_RESET_STATUS3	0x1c
+
+#if BITS_PER_LONG == 64
+#define jh7100_reset_read	readq
+#define jh7100_reset_write	writeq
+#else
+#define jh7100_reset_read	readl
+#define jh7100_reset_write	writel
+#endif
+
+/*
+ * Writing a 1 to the n'th bit of the m'th ASSERT register asserts
+ * line 32m + n, and writing a 0 deasserts the same line.
+ * Most reset lines have their status inverted so a 0 bit in the STATUS
+ * register means the line is asserted and a 1 means it's deasserted. A few
+ * lines don't though, so store the expected value of the status registers when
+ * all lines are asserted.
+ */
+static const DECLARE_BITMAP(jh7100_reset_asserted, 4 * 32) = {
+	BITMAP_FROM_U64(BIT_ULL_MASK(JH7100_RST_U74) |
+			BIT_ULL_MASK(JH7100_RST_VP6_DRESET) |
+			BIT_ULL_MASK(JH7100_RST_VP6_BRESET) |
+			BIT_ULL_MASK(JH7100_RST_HIFI4_DRESET) |
+			BIT_ULL_MASK(JH7100_RST_HIFI4_BRESET)),
+	BITMAP_FROM_U64(BIT_ULL_MASK(JH7100_RST_E24)),
+};
+
+struct jh7100_reset {
+	struct reset_controller_dev rcdev;
+	/* protect registers against concurrent read-modify-write */
+	spinlock_t lock;
+	void __iomem *base;
+};
+
+static inline struct jh7100_reset *
+jh7100_reset_from(struct reset_controller_dev *rcdev)
+{
+	return container_of(rcdev, struct jh7100_reset, rcdev);
+}
+
+static int jh7100_reset_update(struct reset_controller_dev *rcdev,
+			       unsigned long id, bool assert)
+{
+	struct jh7100_reset *data = jh7100_reset_from(rcdev);
+	unsigned long offset = id / BITS_PER_LONG;
+	void __iomem *reg_assert = data->base + JH7100_RESET_ASSERT0 + offset * sizeof(long);
+	void __iomem *reg_status = data->base + JH7100_RESET_STATUS0 + offset * sizeof(long);
+	unsigned long mask = BIT_MASK(id);
+	unsigned long done = jh7100_reset_asserted[offset] & mask;
+	unsigned long value;
+	unsigned long flags;
+	int ret;
+
+	if (!assert)
+		done ^= mask;
+
+	spin_lock_irqsave(&data->lock, flags);
+
+	value = jh7100_reset_read(reg_assert);
+	if (assert)
+		value |= mask;
+	else
+		value &= ~mask;
+	jh7100_reset_write(value, reg_assert);
+
+	/* if the associated clock is gated, deasserting might otherwise hang forever */
+	ret = readx_poll_timeout_atomic(jh7100_reset_read, reg_status, value,
+				        (value & mask) == done, 0, 1000);
+
+	spin_unlock_irqrestore(&data->lock, flags);
+	return ret;
+}
+
+static int jh7100_reset_assert(struct reset_controller_dev *rcdev,
+			       unsigned long id)
+{
+	return jh7100_reset_update(rcdev, id, true);
+}
+
+static int jh7100_reset_deassert(struct reset_controller_dev *rcdev,
+				 unsigned long id)
+{
+	return jh7100_reset_update(rcdev, id, false);
+}
+
+static int jh7100_reset_reset(struct reset_controller_dev *rcdev,
+			      unsigned long id)
+{
+	int ret;
+
+	ret = jh7100_reset_assert(rcdev, id);
+	if (ret)
+		return ret;
+
+	return jh7100_reset_deassert(rcdev, id);
+}
+
+static int jh7100_reset_status(struct reset_controller_dev *rcdev,
+			       unsigned long id)
+{
+	struct jh7100_reset *data = jh7100_reset_from(rcdev);
+	unsigned long offset = id / BITS_PER_LONG;
+	void __iomem *reg_status = data->base + JH7100_RESET_STATUS0 + offset * sizeof(long);
+	unsigned long value = jh7100_reset_read(reg_status);
+	unsigned long mask = BIT_MASK(id);
+
+	return !((value ^ jh7100_reset_asserted[offset]) & mask);
+}
+
+static const struct reset_control_ops jh7100_reset_ops = {
+	.assert		= jh7100_reset_assert,
+	.deassert	= jh7100_reset_deassert,
+	.reset		= jh7100_reset_reset,
+	.status		= jh7100_reset_status,
+};
+
+static int __init jh7100_reset_probe(struct platform_device *pdev)
+{
+	struct jh7100_reset *data;
+
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(data->base))
+		return PTR_ERR(data->base);
+
+	data->rcdev.ops = &jh7100_reset_ops;
+	data->rcdev.owner = THIS_MODULE;
+	data->rcdev.nr_resets = JH7100_RSTN_END;
+	data->rcdev.dev = &pdev->dev;
+	data->rcdev.of_node = pdev->dev.of_node;
+	spin_lock_init(&data->lock);
+
+	return devm_reset_controller_register(&pdev->dev, &data->rcdev);
+}
+
+static const struct of_device_id jh7100_reset_dt_ids[] = {
+	{ .compatible = "starfive,jh7100-reset" },
+	{ /* sentinel */ }
+};
+
+static struct platform_driver jh7100_reset_driver = {
+	.driver = {
+		.name = "jh7100-reset",
+		.of_match_table = jh7100_reset_dt_ids,
+		.suppress_bind_attrs = true,
+	},
+};
+builtin_platform_driver_probe(jh7100_reset_driver, jh7100_reset_probe);
-- 
2.33.1