[PATCH 2/6] clk: add driver for generic clock generators

[Heiko Stuebner <heiko@sntech.de>]

In contrast to fixed clocks that are described as ungateable, boards
sometimes use additional clock generators for things like PCIe reference
clocks, that need actual supplies to get enabled and enable-gpios to be
toggled for them to work.

This adds a driver for those generic unconfigurable clock generators.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
---
 drivers/clk/Kconfig         |   7 ++
 drivers/clk/Makefile        |   1 +
 drivers/clk/clk-generator.c | 133 ++++++++++++++++++++++++++++++++++++
 3 files changed, 141 insertions(+)
 create mode 100644 drivers/clk/clk-generator.c

diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig
index 3e9099504fad4..76c53ddc472ce 100644
--- a/drivers/clk/Kconfig
+++ b/drivers/clk/Kconfig
@@ -247,6 +247,13 @@ config COMMON_CLK_GEMINI
 	  This driver supports the SoC clocks on the Cortina Systems Gemini
 	  platform, also known as SL3516 or CS3516.
 
+config COMMON_CLK_GENERATOR
+	tristate "Clock driver for generic clock generators"
+	depends on GPIOLIB && REGULATOR
+	help
+	  This driver supports generic clock generators that are not
+	  configurable but need supplies to be enabled to run.
+
 config COMMON_CLK_LAN966X
 	tristate "Generic Clock Controller driver for LAN966X SoC"
 	depends on HAS_IOMEM
diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index 4abe16c8ccdfe..9cb0801155771 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -36,6 +36,7 @@ obj-$(CONFIG_COMMON_CLK_FIXED_MMIO)	+= clk-fixed-mmio.o
 obj-$(CONFIG_COMMON_CLK_FSL_FLEXSPI)	+= clk-fsl-flexspi.o
 obj-$(CONFIG_COMMON_CLK_FSL_SAI)	+= clk-fsl-sai.o
 obj-$(CONFIG_COMMON_CLK_GEMINI)		+= clk-gemini.o
+obj-$(CONFIG_COMMON_CLK_GENERATOR)	+= clk-generator.o
 obj-$(CONFIG_COMMON_CLK_ASPEED)		+= clk-aspeed.o
 obj-$(CONFIG_MACH_ASPEED_G6)		+= clk-ast2600.o
 obj-$(CONFIG_ARCH_HIGHBANK)		+= clk-highbank.o
diff --git a/drivers/clk/clk-generator.c b/drivers/clk/clk-generator.c
new file mode 100644
index 0000000000000..99737bab1f5ad
--- /dev/null
+++ b/drivers/clk/clk-generator.c
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2024 Heiko Stuebner <heiko@sntech.de>
+ *
+ * Generic unconfigurable clock generators
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
+#include <linux/slab.h>
+
+struct clk_generator {
+	struct device *dev;
+	struct clk_hw hw;
+	u32 rate;
+	struct regulator *supply;
+	struct gpio_desc *enable_gpio;
+};
+
+#define to_clk_generator(_hw) container_of(_hw, struct clk_generator, hw)
+
+static int clk_generator_prepare(struct clk_hw *hw)
+{
+	return regulator_enable(to_clk_generator(hw)->supply);
+}
+
+static void clk_generator_unprepare(struct clk_hw *hw)
+{
+	regulator_disable(to_clk_generator(hw)->supply);
+}
+
+static int clk_generator_enable(struct clk_hw *hw)
+{
+	gpiod_set_value(to_clk_generator(hw)->enable_gpio, 1);
+	return 0;
+}
+
+static void clk_generator_disable(struct clk_hw *hw)
+{
+	gpiod_set_value(to_clk_generator(hw)->enable_gpio, 0);
+}
+
+static unsigned long clk_generator_recalc_rate(struct clk_hw *hw,
+					       unsigned long parent_rate)
+{
+	return to_clk_generator(hw)->rate;
+}
+
+const struct clk_ops clk_generator_ops = {
+	.prepare = clk_generator_prepare,
+	.unprepare = clk_generator_unprepare,
+	.enable = clk_generator_enable,
+	.disable = clk_generator_disable,
+	.recalc_rate = clk_generator_recalc_rate,
+};
+
+static int clk_generator_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct clk_generator *clkgen;
+	const char *clk_name;
+	int ret;
+
+	clkgen = devm_kzalloc(dev, sizeof(*clkgen), GFP_KERNEL);
+	if (!clkgen)
+		return -ENOMEM;
+
+	clkgen->dev = dev;
+
+	if (device_property_read_u32(dev, "clock-frequency", &clkgen->rate))
+		return -EIO;
+
+	ret = device_property_read_string(dev, "clock-output-names", &clk_name);
+	if (ret)
+		clk_name = fwnode_get_name(dev->fwnode);
+
+	clkgen->supply = devm_regulator_get_optional(dev, "vdd");
+	if (IS_ERR(clkgen->supply)) {
+		if (PTR_ERR(clkgen->supply) != -ENODEV)
+			return dev_err_probe(dev, PTR_ERR(clkgen->supply),
+					     "failed to get regulator\n");
+		clkgen->supply = NULL;
+	}
+
+	clkgen->enable_gpio = devm_gpiod_get_optional(dev, "enable",
+						      GPIOD_OUT_LOW);
+	if (IS_ERR(clkgen->enable_gpio))
+		return dev_err_probe(dev, PTR_ERR(clkgen->enable_gpio),
+				     "failed to get gpio\n");
+
+	ret = gpiod_direction_output(clkgen->enable_gpio, 0);
+	if (ret < 0)
+		return ret;
+
+	clkgen->hw.init = CLK_HW_INIT_NO_PARENT(clk_name, &clk_generator_ops, 0);
+
+	/* register the clock */
+	ret = devm_clk_hw_register(dev, &clkgen->hw);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "failed to register clock\n");
+
+	ret = devm_of_clk_add_hw_provider(dev, of_clk_hw_simple_get,
+					  &clkgen->hw);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "failed to register clock provider\n");
+
+	return 0;
+}
+
+static const struct of_device_id clk_generator_ids[] = {
+	{ .compatible = "clock-generator" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, clk_generator_ids);
+
+static struct platform_driver clk_generator_driver = {
+	.driver = {
+		.name = "clk_generator",
+		.of_match_table = clk_generator_ids,
+	},
+	.probe = clk_generator_probe,
+};
+module_platform_driver(clk_generator_driver);
+
+MODULE_AUTHOR("Heiko Stuebner <heiko@sntech.de>");
+MODULE_DESCRIPTION("Clock-generator driver");
+MODULE_LICENSE("GPL");
-- 
2.39.2