clk: ralink: make system controller node a reset provider

MT7621 system controller node is already providing the clocks for the whole
system but must also serve as a reset provider. Hence, add reset controller
related code to the clock driver itself. To get resets properly ready for
the rest of the world we need to move platform driver initialization process
to 'arch_initcall'.

CC: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Link: https://lore.kernel.org/r/20220210094859.927868-3-sergio.paracuellos@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/clk/ralink/clk-mt7621.c

@@ -11,14 +11,17 @@
 #include <linux/mfd/syscon.h>
 #include <linux/platform_device.h>
 #include <linux/regmap.h>
+#include <linux/reset-controller.h>
 #include <linux/slab.h>
 #include <dt-bindings/clock/mt7621-clk.h>
+#include <dt-bindings/reset/mt7621-reset.h>
 
 /* Configuration registers */
 #define SYSC_REG_SYSTEM_CONFIG0         0x10
 #define SYSC_REG_SYSTEM_CONFIG1         0x14
 #define SYSC_REG_CLKCFG0		0x2c
 #define SYSC_REG_CLKCFG1		0x30
+#define SYSC_REG_RESET_CTRL		0x34
 #define SYSC_REG_CUR_CLK_STS		0x44
 #define MEMC_REG_CPU_PLL		0x648
 
@@ -398,6 +401,82 @@ free_clk_priv:
 }
 CLK_OF_DECLARE_DRIVER(mt7621_clk, "mediatek,mt7621-sysc", mt7621_clk_init);
 
+struct mt7621_rst {
+	struct reset_controller_dev rcdev;
+	struct regmap *sysc;
+};
+
+static struct mt7621_rst *to_mt7621_rst(struct reset_controller_dev *dev)
+{
+	return container_of(dev, struct mt7621_rst, rcdev);
+}
+
+static int mt7621_assert_device(struct reset_controller_dev *rcdev,
+				unsigned long id)
+{
+	struct mt7621_rst *data = to_mt7621_rst(rcdev);
+	struct regmap *sysc = data->sysc;
+
+	return regmap_update_bits(sysc, SYSC_REG_RESET_CTRL, BIT(id), BIT(id));
+}
+
+static int mt7621_deassert_device(struct reset_controller_dev *rcdev,
+				  unsigned long id)
+{
+	struct mt7621_rst *data = to_mt7621_rst(rcdev);
+	struct regmap *sysc = data->sysc;
+
+	return regmap_update_bits(sysc, SYSC_REG_RESET_CTRL, BIT(id), 0);
+}
+
+static int mt7621_reset_device(struct reset_controller_dev *rcdev,
+			       unsigned long id)
+{
+	int ret;
+
+	ret = mt7621_assert_device(rcdev, id);
+	if (ret < 0)
+		return ret;
+
+	return mt7621_deassert_device(rcdev, id);
+}
+
+static int mt7621_rst_xlate(struct reset_controller_dev *rcdev,
+			    const struct of_phandle_args *reset_spec)
+{
+	unsigned long id = reset_spec->args[0];
+
+	if (id == MT7621_RST_SYS || id >= rcdev->nr_resets)
+		return -EINVAL;
+
+	return id;
+}
+
+static const struct reset_control_ops reset_ops = {
+	.reset = mt7621_reset_device,
+	.assert = mt7621_assert_device,
+	.deassert = mt7621_deassert_device
+};
+
+static int mt7621_reset_init(struct device *dev, struct regmap *sysc)
+{
+	struct mt7621_rst *rst_data;
+
+	rst_data = devm_kzalloc(dev, sizeof(*rst_data), GFP_KERNEL);
+	if (!rst_data)
+		return -ENOMEM;
+
+	rst_data->sysc = sysc;
+	rst_data->rcdev.ops = &reset_ops;
+	rst_data->rcdev.owner = THIS_MODULE;
+	rst_data->rcdev.nr_resets = 32;
+	rst_data->rcdev.of_reset_n_cells = 1;
+	rst_data->rcdev.of_xlate = mt7621_rst_xlate;
+	rst_data->rcdev.of_node = dev_of_node(dev);
+
+	return devm_reset_controller_register(dev, &rst_data->rcdev);
+}
+
 static int mt7621_clk_probe(struct platform_device *pdev)
 {
 	struct device_node *np = pdev->dev.of_node;
@@ -424,6 +503,12 @@ static int mt7621_clk_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	ret = mt7621_reset_init(dev, priv->sysc);
+	if (ret) {
+		dev_err(dev, "Could not init reset controller\n");
+		return ret;
+	}
+
 	count = ARRAY_SIZE(mt7621_clks_base) +
 		ARRAY_SIZE(mt7621_fixed_clks) + ARRAY_SIZE(mt7621_gates);
 	clk_data = devm_kzalloc(dev, struct_size(clk_data, hws, count),
@@ -485,4 +570,9 @@ static struct platform_driver mt7621_clk_driver = {
 		.of_match_table = mt7621_clk_of_match,
 	},
 };
-builtin_platform_driver(mt7621_clk_driver);
+
+static int __init mt7621_clk_reset_init(void)
+{
+	return platform_driver_register(&mt7621_clk_driver);
+}
+arch_initcall(mt7621_clk_reset_init);