[RFC v3 08/18] reset: thead: Add TH1520 reset controller driver

[Michal Wilczynski <m.wilczynski@samsung.com>]

Introduce reset controller driver for the T-HEAD TH1520 SoC. The
controller manages hardware reset lines for various SoC subsystems, such
as the GPU. By exposing these resets via the Linux reset subsystem,
drivers can request and control hardware resets to reliably initialize
or recover key components.

Signed-off-by: Michal Wilczynski <m.wilczynski@samsung.com>
---
 MAINTAINERS                  |   1 +
 drivers/reset/Kconfig        |  10 +++
 drivers/reset/Makefile       |   1 +
 drivers/reset/reset-th1520.c | 144 +++++++++++++++++++++++++++++++++++
 4 files changed, 156 insertions(+)
 create mode 100644 drivers/reset/reset-th1520.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 1b6e894500ef..18382a356b12 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -20197,6 +20197,7 @@ F:	drivers/mailbox/mailbox-th1520.c
 F:	drivers/net/ethernet/stmicro/stmmac/dwmac-thead.c
 F:	drivers/pinctrl/pinctrl-th1520.c
 F:	drivers/pmdomain/thead/
+F:	drivers/reset/reset-th1520.c
 F:	include/dt-bindings/clock/thead,th1520-clk-ap.h
 F:	include/dt-bindings/firmware/thead,th1520-aon.h
 F:	include/linux/firmware/thead/thead,th1520-aon.h
diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
index 5b3abb6db248..fa0943c3d1de 100644
--- a/drivers/reset/Kconfig
+++ b/drivers/reset/Kconfig
@@ -272,6 +272,16 @@ config RESET_SUNXI
 	help
 	  This enables the reset driver for Allwinner SoCs.
 
+config RESET_TH1520
+	tristate "T-HEAD 1520 reset controller"
+	depends on ARCH_THEAD || COMPILE_TEST
+	select REGMAP_MMIO
+	help
+	  This driver provides support for the T-HEAD TH1520 SoC reset controller,
+	  which manages hardware reset lines for SoC components such as the GPU.
+	  Enable this option if you need to control hardware resets on TH1520-based
+	  systems.
+
 config RESET_TI_SCI
 	tristate "TI System Control Interface (TI-SCI) reset driver"
 	depends on TI_SCI_PROTOCOL || (COMPILE_TEST && TI_SCI_PROTOCOL=n)
diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
index 677c4d1e2632..d6c2774407ae 100644
--- a/drivers/reset/Makefile
+++ b/drivers/reset/Makefile
@@ -35,6 +35,7 @@ obj-$(CONFIG_RESET_SIMPLE) += reset-simple.o
 obj-$(CONFIG_RESET_SOCFPGA) += reset-socfpga.o
 obj-$(CONFIG_RESET_SUNPLUS) += reset-sunplus.o
 obj-$(CONFIG_RESET_SUNXI) += reset-sunxi.o
+obj-$(CONFIG_RESET_TH1520) += reset-th1520.o
 obj-$(CONFIG_RESET_TI_SCI) += reset-ti-sci.o
 obj-$(CONFIG_RESET_TI_SYSCON) += reset-ti-syscon.o
 obj-$(CONFIG_RESET_TI_TPS380X) += reset-tps380x.o
diff --git a/drivers/reset/reset-th1520.c b/drivers/reset/reset-th1520.c
new file mode 100644
index 000000000000..e4278f49c62f
--- /dev/null
+++ b/drivers/reset/reset-th1520.c
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2024 Samsung Electronics Co., Ltd.
+ * Author: Michal Wilczynski <m.wilczynski@samsung.com>
+ */
+
+#include <linux/mod_devicetable.h>
+#include <linux/platform_device.h>
+#include <linux/reset-controller.h>
+#include <linux/regmap.h>
+
+ /* register offset in VOSYS_REGMAP */
+#define TH1520_GPU_RST_CFG		0x0
+#define TH1520_GPU_RST_CFG_MASK		GENMASK(2, 0)
+
+/* register values */
+#define TH1520_GPU_SW_GPU_RST		BIT(0)
+#define TH1520_GPU_SW_CLKGEN_RST	BIT(1)
+
+struct th1520_reset_priv {
+	struct reset_controller_dev rcdev;
+	struct regmap *map;
+};
+
+static inline struct th1520_reset_priv *
+to_th1520_reset(struct reset_controller_dev *rcdev)
+{
+	return container_of(rcdev, struct th1520_reset_priv, rcdev);
+}
+
+static void th1520_rst_gpu_enable(struct regmap *reg)
+{
+	int val;
+
+	/* if the GPU is not in a reset state it, put it into one */
+	regmap_read(reg, TH1520_GPU_RST_CFG, &val);
+	if (val)
+		regmap_update_bits(reg, TH1520_GPU_RST_CFG,
+				   TH1520_GPU_RST_CFG_MASK, 0x0);
+
+	/* rst gpu clkgen */
+	regmap_set_bits(reg, TH1520_GPU_RST_CFG, TH1520_GPU_SW_CLKGEN_RST);
+
+	/*
+	 * According to the hardware manual, a delay of at least 32 clock
+	 * cycles is required between de-asserting the clkgen reset and
+	 * de-asserting the GPU reset. Assuming a worst-case scenario with
+	 * a very high GPU clock frequency, a delay of 1 microsecond is
+	 * sufficient to ensure this requirement is met across all
+	 * feasible GPU clock speeds.
+	 */
+	udelay(1);
+
+	/* rst gpu */
+	regmap_set_bits(reg, TH1520_GPU_RST_CFG, TH1520_GPU_SW_GPU_RST);
+}
+
+static void th1520_rst_gpu_disable(struct regmap *reg)
+{
+	regmap_update_bits(reg, TH1520_GPU_RST_CFG, TH1520_GPU_RST_CFG_MASK, 0x0);
+}
+
+static int th1520_reset_assert(struct reset_controller_dev *rcdev, unsigned long id)
+{
+	struct th1520_reset_priv *priv = to_th1520_reset(rcdev);
+
+	th1520_rst_gpu_disable(priv->map);
+
+	return 0;
+}
+
+static int th1520_reset_deassert(struct reset_controller_dev *rcdev, unsigned long id)
+{
+	struct th1520_reset_priv *priv = to_th1520_reset(rcdev);
+
+	th1520_rst_gpu_enable(priv->map);
+
+	return 0;
+}
+
+static int th1520_reset_xlate(struct reset_controller_dev *rcdev,
+			      const struct of_phandle_args *reset_spec)
+{
+	return 0;
+}
+
+static const struct reset_control_ops th1520_reset_ops = {
+	.assert	= th1520_reset_assert,
+	.deassert = th1520_reset_deassert,
+};
+
+static const struct regmap_config th1520_reset_regmap_config = {
+	.reg_bits = 32,
+	.val_bits = 32,
+	.reg_stride = 4,
+	.fast_io = true,
+};
+
+static int th1520_reset_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct th1520_reset_priv *priv;
+	void __iomem *base;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(base))
+		return PTR_ERR(base);
+
+	priv->map = devm_regmap_init_mmio(dev, base,
+					  &th1520_reset_regmap_config);
+	if (IS_ERR(priv->map))
+		return PTR_ERR(priv->map);
+
+	priv->rcdev.owner = THIS_MODULE;
+	priv->rcdev.nr_resets = 1;
+	priv->rcdev.ops = &th1520_reset_ops;
+	priv->rcdev.of_node = dev->of_node;
+	priv->rcdev.of_xlate = th1520_reset_xlate;
+
+	return devm_reset_controller_register(dev, &priv->rcdev);
+}
+
+static const struct of_device_id th1520_reset_match[] = {
+	{ .compatible = "thead,th1520-reset" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, th1520_reset_match);
+
+static struct platform_driver th1520_reset_driver = {
+	.driver = {
+		.name = "th1520-reset",
+		.of_match_table = th1520_reset_match,
+	},
+	.probe = th1520_reset_probe,
+};
+module_platform_driver(th1520_reset_driver);
+
+MODULE_AUTHOR("Michal Wilczynski <m.wilczynski@samsung.com>");
+MODULE_DESCRIPTION("T-HEAD TH1520 SoC reset controller");
+MODULE_LICENSE("GPL");
-- 
2.34.1