clk: virt: Add virtual CPU clock driver

Signed-off-by: Leo Yan <leo.yan@linaro.org>

drivers/clk/Makefile

@@ -138,3 +138,5 @@ endif
 obj-y					+= xilinx/
 obj-$(CONFIG_ARCH_ZYNQ)			+= zynq/
 obj-$(CONFIG_COMMON_CLK_ZYNQMP)         += zynqmp/
+
+obj-y					+= clk-virt-2.8-cpu.o

drivers/clk/clk-virt-2.8-cpu.c

+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Linaro virt clock driver
+ *
+ * Copyright (c) 2021 Linaro Limited.
+ *
+ * Author: Leo Yan <leo.yan@linaro.org>
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/mailbox_client.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+#define DEFINE_VIRT_CLK(_id, _name, _rate)			\
+	{							\
+		.id = (_id),					\
+		.hw.init = &(struct clk_init_data) {		\
+			.name = #_name,				\
+			.ops = &virt_clk_ops,			\
+			.num_parents = 0,			\
+			.flags = CLK_GET_RATE_NOCACHE,		\
+		},						\
+		.rate = (_rate),				\
+	},
+
+#define to_virt_clk(_hw) container_of(_hw, struct virt_clk, hw)
+
+struct virt_clk {
+	unsigned int id;
+	struct clk_hw hw;
+	unsigned int rate;
+};
+
+static unsigned long virt_clk_recalc_rate(struct clk_hw *hw,
+						 unsigned long parent_rate)
+{
+	struct virt_clk *virt_clk = to_virt_clk(hw);
+
+	return virt_clk->rate;
+}
+
+static long virt_clk_round_rate(struct clk_hw *hw, unsigned long rate,
+				       unsigned long *prate)
+{
+	/*
+	 * LPM3 handles rate rounding so just return whatever
+	 * rate is requested.
+	 */
+	return rate;
+}
+
+static int virt_clk_set_rate(struct clk_hw *hw, unsigned long rate,
+				    unsigned long parent_rate)
+{
+	struct virt_clk *virt_clk = to_virt_clk(hw);
+
+	virt_clk->rate = rate;
+	return 0;
+}
+
+static const struct clk_ops virt_clk_ops = {
+	.recalc_rate    = virt_clk_recalc_rate,
+	.round_rate     = virt_clk_round_rate,
+	.set_rate       = virt_clk_set_rate,
+};
+
+static struct virt_clk virt_clks[2] = {
+	DEFINE_VIRT_CLK(0, "cpu-cluster.0", 533000000)
+	DEFINE_VIRT_CLK(1, "cpu-cluster.1", 533000000)
+};
+
+static struct clk_hw *virt_clk_hw_get(struct of_phandle_args *clkspec,
+				      void *data)
+{
+	unsigned int idx = clkspec->args[0];
+
+	if (idx >= 2) {
+		pr_err("%s: invalid index %u\n", __func__, idx);
+		return ERR_PTR(-EINVAL);
+	}
+
+	return &virt_clks[idx].hw;
+}
+
+static int virt_clk_probe(struct platform_device *pdev)
+{
+	unsigned int i;
+	int ret;
+
+	for (i = 0; i < 2; i++) {
+		ret = devm_clk_hw_register(&pdev->dev, &virt_clks[i].hw);
+		if (ret)
+			return ret;
+	}
+
+	return devm_of_clk_add_hw_provider(&pdev->dev, virt_clk_hw_get,
+					   virt_clks);
+}
+
+static const struct of_device_id virt_clk_of_match[] = {
+	{ .compatible = "linaro,virt-2.8-cpu-clk", },
+	{}
+};
+
+static struct platform_driver virt_clk_driver = {
+	.probe	= virt_clk_probe,
+	.driver = {
+		.name = "virt-2.8-cpu-clk",
+		.of_match_table = virt_clk_of_match,
+	},
+};
+
+static int __init virt_clk_init(void)
+{
+	return platform_driver_register(&virt_clk_driver);
+}
+subsys_initcall(virt_clk_init);