clk: Add support for Arm's Versatile Express OSC clock generators

The Arm Versatile Express and Juno development boards contain an
OSC clock generator that can be accessed through the Versatile
Express config bus. The generators are quite often being controlled
by some MCU and the config bus offers a uniform way of exposing them.

Signed-off-by: Liviu Dudau <liviu.dudau@foss.arm.com>
Reviewed-by: Heiko Schocher <hs@denx.de>

drivers/clk/Kconfig

@@ -68,6 +68,13 @@ config CLK_HSDK
 	help
 	  Enable this to support the cgu clocks on Synopsys ARC HSDK
 
+config CLK_VEXPRESS_OSC
+	bool "Enable driver for Arm Versatile Express OSC clock generators"
+	depends on CLK && VEXPRESS_CONFIG
+	help
+	  This clock driver adds support for clock generators present on
+	  Arm Versatile Express platforms.
+
 config CLK_ZYNQ
 	bool "Enable clock driver support for Zynq"
 	depends on CLK && ARCH_ZYNQ

drivers/clk/Makefile

@@ -24,6 +24,7 @@ obj-$(CONFIG_CLK_RENESAS) += renesas/
 obj-$(CONFIG_CLK_STM32F) += clk_stm32f.o
 obj-$(CONFIG_CLK_STM32MP1) += clk_stm32mp1.o
 obj-$(CONFIG_CLK_UNIPHIER) += uniphier/
+obj-$(CONFIG_CLK_VEXPRESS_OSC) += clk_vexpress_osc.o
 obj-$(CONFIG_CLK_ZYNQ) += clk_zynq.o
 obj-$(CONFIG_CLK_ZYNQMP) += clk_zynqmp.o
 obj-$(CONFIG_ICS8N3QV01) += ics8n3qv01.o

drivers/clk/clk_vexpress_osc.c

@@ -0,0 +1,109 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2018 Arm Ltd
+ * Author: Liviu Dudau <liviu.dudau@foss.arm.com>
+ *
+ */
+#define DEBUG
+#include <common.h>
+#include <clk-uclass.h>
+#include <dm.h>
+#include <dm/lists.h>
+#include <errno.h>
+#include <misc.h>
+
+#define CLK_FUNCTION		BIT(20)
+
+struct vexpress_osc_clk_priv {
+	u8 osc;
+	ulong rate_min;
+	ulong rate_max;
+};
+
+static ulong vexpress_osc_clk_get_rate(struct clk *clk)
+{
+	int err;
+	u32 data;
+	struct udevice *vexpress_cfg = dev_get_parent(clk->dev);
+	struct vexpress_osc_clk_priv *priv = dev_get_priv(clk->dev);
+
+	data = CLK_FUNCTION | priv->osc;
+	err = misc_read(vexpress_cfg, 0, &data, sizeof(data));
+	if (err)
+		return err;
+
+	return data;
+}
+
+#ifndef CONFIG_SPL_BUILD
+static ulong vexpress_osc_clk_set_rate(struct clk *clk, ulong rate)
+{
+	int err;
+	u32 buffer[2];
+	struct udevice *vexpress_cfg = dev_get_parent(clk->dev);
+	struct vexpress_osc_clk_priv *priv = dev_get_priv(clk->dev);
+
+	if (rate < priv->rate_min || rate > priv->rate_max)
+		return -EINVAL;
+
+	/*
+	 * we are sending the parent the info about the oscillator
+	 * and the value we want to set
+	 */
+	buffer[0] = CLK_FUNCTION | priv->osc;
+	buffer[1] = rate;
+	err = misc_write(vexpress_cfg, 0, buffer, 2 * sizeof(u32));
+	if (err)
+		return err;
+
+	return rate;
+}
+#endif
+
+static struct clk_ops vexpress_osc_clk_ops = {
+	.get_rate = vexpress_osc_clk_get_rate,
+#ifndef CONFIG_SPL_BUILD
+	.set_rate = vexpress_osc_clk_set_rate,
+#endif
+};
+
+static int vexpress_osc_clk_probe(struct udevice *dev)
+{
+	struct vexpress_osc_clk_priv *priv = dev_get_priv(dev);
+	u32 values[2];
+	int err;
+
+	err = dev_read_u32_array(dev, "freq-range", values, 2);
+	if (err)
+		return err;
+	priv->rate_min = values[0];
+	priv->rate_max = values[1];
+
+	err = dev_read_u32_array(dev, "arm,vexpress-sysreg,func", values, 2);
+	if (err)
+		return err;
+
+	if (values[0] != 1) {
+		dev_err(dev, "Invalid VExpress function for clock, must be '1'");
+		return -EINVAL;
+	}
+	priv->osc = values[1];
+	debug("clk \"%s%d\", min freq %luHz, max freq %luHz\n", dev->name,
+	      priv->osc, priv->rate_min, priv->rate_max);
+
+	return 0;
+}
+
+static const struct udevice_id vexpress_osc_clk_ids[] = {
+	{ .compatible = "arm,vexpress-osc", },
+	{}
+};
+
+U_BOOT_DRIVER(vexpress_osc_clk) = {
+	.name = "vexpress_osc_clk",
+	.id = UCLASS_CLK,
+	.of_match = vexpress_osc_clk_ids,
+	.ops = &vexpress_osc_clk_ops,
+	.priv_auto_alloc_size = sizeof(struct vexpress_osc_clk_priv),
+	.probe = vexpress_osc_clk_probe,
+};