clk: Add GPIO-controlled clock gate driver

Add driver which implements GPIO-controlled clock. The GPIO is used
as a gate to enable/disable the clock. This matches linux clk-gpio.c
driver, however this does not implement the GPIO mux part, which in
U-Boot DM would be better fit in separate driver.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Reviewed-by: Sean Anderson <seanga2@gmail.com>

drivers/clk/Kconfig

@@ -83,6 +83,19 @@ config CLK_COMPOSITE_CCF
 	  Enable this option if you want to (re-)use the Linux kernel's Common
 	  Clock Framework [CCF] composite code in U-Boot's clock driver.
 
+config CLK_GPIO
+	bool "GPIO-controlled clock gate driver"
+	depends on CLK
+	help
+	  Enable this option to add GPIO-controlled clock gate driver.
+
+config SPL_CLK_GPIO
+	bool "GPIO-controlled clock gate driver in SPL"
+	depends on SPL_CLK
+	help
+	  Enable this option to add GPIO-controlled clock gate driver
+	  in U-Boot SPL.
+
 config CLK_BCM6345
 	bool "Clock controller driver for BCM6345"
 	depends on CLK && ARCH_BMIPS

drivers/clk/Makefile

@@ -10,6 +10,7 @@ obj-$(CONFIG_$(SPL_TPL_)CLK) += clk_fixed_factor.o
 obj-$(CONFIG_$(SPL_TPL_)CLK_CCF) += clk.o clk-divider.o clk-mux.o clk-gate.o
 obj-$(CONFIG_$(SPL_TPL_)CLK_CCF) += clk-fixed-factor.o
 obj-$(CONFIG_$(SPL_TPL_)CLK_COMPOSITE_CCF) += clk-composite.o
+obj-$(CONFIG_$(SPL_TPL_)CLK_GPIO) += clk-gpio.o
 
 obj-y += analogbits/
 obj-y += imx/

drivers/clk/clk-gpio.c

@@ -0,0 +1,66 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2023 Marek Vasut <marek.vasut+renesas@mailbox.org>
+ */
+
+#include <asm/gpio.h>
+#include <common.h>
+#include <clk-uclass.h>
+#include <dm.h>
+
+struct clk_gpio_priv {
+	struct gpio_desc	enable;
+};
+
+static int clk_gpio_enable(struct clk *clk)
+{
+	struct clk_gpio_priv *priv = dev_get_priv(clk->dev);
+
+	dm_gpio_set_value(&priv->enable, 1);
+
+	return 0;
+}
+
+static int clk_gpio_disable(struct clk *clk)
+{
+	struct clk_gpio_priv *priv = dev_get_priv(clk->dev);
+
+	dm_gpio_set_value(&priv->enable, 0);
+
+	return 0;
+}
+
+const struct clk_ops clk_gpio_ops = {
+	.enable		= clk_gpio_enable,
+	.disable	= clk_gpio_disable,
+};
+
+static int clk_gpio_probe(struct udevice *dev)
+{
+	struct clk_gpio_priv *priv = dev_get_priv(dev);
+
+	return gpio_request_by_name(dev, "enable-gpios", 0,
+				    &priv->enable, GPIOD_IS_OUT);
+}
+
+/*
+ * When implementing clk-mux-clock, use gpio_request_list_by_name
+ * and implement get_rate/set_rate/set_parent ops. This should be
+ * in a separate driver and with separate Kconfig option to enable
+ * that driver, since unlike Linux implementation, the U-Boot DM
+ * integration would be orthogonal to this driver.
+ */
+static const struct udevice_id clk_gpio_match[] = {
+	{ .compatible = "gpio-gate-clock" },
+	{ /* sentinel */ }
+};
+
+U_BOOT_DRIVER(gpio_gate_clock) = {
+	.name		= "gpio_clock",
+	.id		= UCLASS_CLK,
+	.of_match	= clk_gpio_match,
+	.probe		= clk_gpio_probe,
+	.priv_auto	= sizeof(struct clk_gpio_priv),
+	.ops		= &clk_gpio_ops,
+	.flags		= DM_FLAG_PRE_RELOC,
+};