riscv: Add a SYSCON driver for SiFive's Core Local Interruptor

This adds U-Boot syscon driver for SiFive's Core Local Interruptor
(CLINT). The CLINT block holds memory-mapped control and status
registers associated with software and timer interrupts.

This driver implements the riscv_get_time() API as required by
the generic RISC-V timer driver, as well as some other APIs that
are needed for handling IPI.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
Reviewed-by: Anup Patel <anup@brainfault.org>

arch/riscv/Kconfig

@@ -95,4 +95,13 @@ config 32BIT
 config 64BIT
 	bool
 
+config SIFIVE_CLINT
+	bool
+	depends on RISCV_MMODE
+	select REGMAP
+	select SYSCON
+	help
+	  The SiFive CLINT block holds memory-mapped control and status registers
+	  associated with software and timer interrupts.
+
 endmenu

arch/riscv/include/asm/global_data.h

@@ -12,6 +12,9 @@
 
 /* Architecture-specific global data */
 struct arch_global_data {
+#ifdef CONFIG_SIFIVE_CLINT
+	void __iomem *clint;	/* clint base address */
+#endif
 };
 
 #include <asm-generic/global_data.h>

arch/riscv/include/asm/syscon.h

@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (C) 2018, Bin Meng <bmeng.cn@gmail.com>
+ */
+
+#ifndef _ASM_SYSCON_H
+#define _ASM_SYSCON_H
+
+/*
+ * System controllers in a RISC-V system
+ *
+ * So far only SiFive's Core Local Interruptor (CLINT) is defined.
+ */
+enum {
+	RISCV_NONE,
+	RISCV_SYSCON_CLINT,	/* Core Local Interruptor (CLINT) */
+};
+
+#endif /* _ASM_SYSCON_H */

arch/riscv/lib/Makefile

@@ -9,6 +9,7 @@
 obj-$(CONFIG_CMD_BOOTM) += bootm.o
 obj-$(CONFIG_CMD_GO) += boot.o
 obj-y	+= cache.o
+obj-$(CONFIG_SIFIVE_CLINT) += sifive_clint.o
 obj-y	+= interrupts.o
 obj-y	+= reset.o
 obj-y   += setjmp.o

arch/riscv/lib/sifive_clint.c

@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2018, Bin Meng <bmeng.cn@gmail.com>
+ *
+ * U-Boot syscon driver for SiFive's Core Local Interruptor (CLINT).
+ * The CLINT block holds memory-mapped control and status registers
+ * associated with software and timer interrupts.
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <regmap.h>
+#include <syscon.h>
+#include <asm/io.h>
+#include <asm/syscon.h>
+
+/* MSIP registers */
+#define MSIP_REG(base, hart)		((ulong)(base) + (hart) * 4)
+/* mtime compare register */
+#define MTIMECMP_REG(base, hart)	((ulong)(base) + 0x4000 + (hart) * 8)
+/* mtime register */
+#define MTIME_REG(base)			((ulong)(base) + 0xbff8)
+
+DECLARE_GLOBAL_DATA_PTR;
+
+#define CLINT_BASE_GET(void)						\
+	do {								\
+		long *ret;						\
+									\
+		if (!gd->arch.clint) {					\
+			ret = syscon_get_first_range(RISCV_SYSCON_CLINT); \
+			if (IS_ERR(ret))				\
+				return PTR_ERR(ret);			\
+			gd->arch.clint = ret;				\
+		}							\
+	} while (0)
+
+int riscv_get_time(u64 *time)
+{
+	CLINT_BASE_GET();
+
+	*time = readq((void __iomem *)MTIME_REG(gd->arch.clint));
+
+	return 0;
+}
+
+int riscv_set_timecmp(int hart, u64 cmp)
+{
+	CLINT_BASE_GET();
+
+	writeq(cmp, (void __iomem *)MTIMECMP_REG(gd->arch.clint, hart));
+
+	return 0;
+}
+
+int riscv_send_ipi(int hart)
+{
+	CLINT_BASE_GET();
+
+	writel(1, (void __iomem *)MSIP_REG(gd->arch.clint, hart));
+
+	return 0;
+}
+
+int riscv_clear_ipi(int hart)
+{
+	CLINT_BASE_GET();
+
+	writel(0, (void __iomem *)MSIP_REG(gd->arch.clint, hart));
+
+	return 0;
+}
+
+static const struct udevice_id sifive_clint_ids[] = {
+	{ .compatible = "riscv,clint0", .data = RISCV_SYSCON_CLINT },
+	{ }
+};
+
+U_BOOT_DRIVER(sifive_clint) = {
+	.name		= "sifive_clint",
+	.id		= UCLASS_SYSCON,
+	.of_match	= sifive_clint_ids,
+	.flags		= DM_FLAG_PRE_RELOC,
+};