drivers: cpu: Add xtensa CPU driver

Implement various CPU related functions.
I'm actually just using it to get cpu clock frequency.

Tested-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>

drivers/cpu/Kconfig

@@ -33,3 +33,9 @@ config CPU_MICROBLAZE
 	select XILINX_MICROBLAZE0_PVR
 	help
 	  Support CPU cores for Microblaze architecture.
+
+config CPU_XTENSA
+	bool "Enable Xtensa CPU driver"
+	depends on CPU && XTENSA
+	help
+	  Support CPU cores for Xtensa architecture.

drivers/cpu/Makefile

@@ -14,4 +14,5 @@ obj-$(CONFIG_CPU_IMX) += imx8_cpu.o
 obj-$(CONFIG_CPU_MPC83XX) += mpc83xx_cpu.o
 obj-$(CONFIG_CPU_RISCV) += riscv_cpu.o
 obj-$(CONFIG_CPU_MICROBLAZE) += microblaze_cpu.o
+obj-$(CONFIG_CPU_XTENSA) += xtensa_cpu.o
 obj-$(CONFIG_SANDBOX) += cpu_sandbox.o

drivers/cpu/xtensa_cpu.c

@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2024 Jiaxun Yang <jiaxun.yang@flygoat.com>
+ */
+
+#include <clk.h>
+#include <cpu.h>
+#include <dm.h>
+#include <errno.h>
+#include <linux/bitops.h>
+#include <linux/err.h>
+
+#include <asm/arch/core.h>
+
+static int xtensa_cpu_get_desc(const struct udevice *dev, char *buf, int size)
+{
+	const char *cpu = XCHAL_CORE_ID;
+
+	if (!cpu || size < (strlen(cpu) + 1))
+		return -ENOSPC;
+
+	strcpy(buf, cpu);
+
+	return 0;
+}
+
+static int xtensa_cpu_get_info(const struct udevice *dev, struct cpu_info *info)
+{
+	struct cpu_plat *plat = dev_get_parent_plat(dev);
+
+	info->cpu_freq = plat->timebase_freq;
+
+#if XCHAL_HAVE_PTP_MMU
+		info->features |= BIT(CPU_FEAT_MMU);
+#endif
+#if XCHAL_ICACHE_SIZE || XCHAL_DCACHE_SIZE
+		info->features |= BIT(CPU_FEAT_L1_CACHE);
+#endif
+
+	return 0;
+}
+
+static int xtensa_cpu_get_count(const struct udevice *dev)
+{
+	ofnode node;
+	int num = 0;
+
+	ofnode_for_each_subnode(node, dev_ofnode(dev->parent)) {
+		const char *device_type;
+
+		/* skip if hart is marked as not available in the device tree */
+		if (!ofnode_is_enabled(node))
+			continue;
+
+		device_type = ofnode_read_string(node, "device_type");
+		if (!device_type)
+			continue;
+		if (strcmp(device_type, "cpu") == 0)
+			num++;
+	}
+
+	return num;
+}
+
+static int xtensa_cpu_bind(struct udevice *dev)
+{
+	struct cpu_plat *plat = dev_get_parent_plat(dev);
+
+	plat->cpu_id = dev_read_addr(dev);
+
+	return 0;
+}
+
+static int xtensa_cpu_probe(struct udevice *dev)
+{
+	int ret = 0;
+	struct clk clk;
+	struct cpu_plat *plat = dev_get_parent_plat(dev);
+
+	asm volatile ("rsr %0, 176\n"
+		      "rsr %1, 208\n"
+		      : "=r"(plat->id[0]), "=r"(plat->id[1]));
+
+	/* Get a clock if it exists */
+	ret = clk_get_by_index(dev, 0, &clk);
+	if (!ret) {
+		ret = clk_enable(&clk);
+		if (ret && (ret != -ENOSYS || ret != -ENOTSUPP))
+			return ret;
+		ret = clk_get_rate(&clk);
+		if (!IS_ERR_VALUE(ret))
+			plat->timebase_freq = ret;
+	}
+
+	return 0;
+}
+
+static const struct cpu_ops xtensa_cpu_ops = {
+	.get_desc	= xtensa_cpu_get_desc,
+	.get_info	= xtensa_cpu_get_info,
+	.get_count	= xtensa_cpu_get_count,
+};
+
+static const struct udevice_id xtensa_cpu_ids[] = {
+	{ .compatible = "cdns,xtensa-cpu" },
+	{ }
+};
+
+U_BOOT_DRIVER(xtensa_cpu) = {
+	.name = "xtensa_cpu",
+	.id = UCLASS_CPU,
+	.of_match = xtensa_cpu_ids,
+	.bind = xtensa_cpu_bind,
+	.probe = xtensa_cpu_probe,
+	.ops = &xtensa_cpu_ops,
+	.flags = DM_FLAG_PRE_RELOC,
+};