riscv: Add a SYSCON driver for Andestech's PLMT

The platform-Level Machine Timer (PLMT) block
holds memory-mapped mtime register associated
with timer tick.

This driver implements the riscv_get_time() which
is required by the generic RISC-V timer driver.

Signed-off-by: Rick Chen <rick@andestech.com>
Cc: Greentime Hu <greentime@andestech.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>

arch/riscv/Kconfig

@@ -118,6 +118,15 @@ config ANDES_PLIC
 	  The Andes PLIC block holds memory-mapped claim and pending registers
 	  associated with software interrupt.
 
+config ANDES_PLMT
+	bool
+	depends on RISCV_MMODE
+	select REGMAP
+	select SYSCON
+	help
+	  The Andes PLMT block holds memory-mapped mtime register
+	  associated with timer tick.
+
 config RISCV_RDTIME
 	bool
 	default y if RISCV_SMODE

arch/riscv/include/asm/global_data.h

@@ -21,6 +21,9 @@ struct arch_global_data {
 #ifdef CONFIG_ANDES_PLIC
 	void __iomem *plic;	/* plic base address */
 #endif
+#ifdef CONFIG_ANDES_PLMT
+	void __iomem *plmt;	/* plmt base address */
+#endif
 #ifdef CONFIG_SMP
 	struct ipi_data ipi[CONFIG_NR_CPUS];
 #endif

arch/riscv/include/asm/syscon.h

@@ -13,6 +13,7 @@ enum {
 	RISCV_NONE,
 	RISCV_SYSCON_CLINT,	/* Core Local Interruptor (CLINT) */
 	RISCV_SYSCON_PLIC,	/* Platform Level Interrupt Controller (PLIC) */
+	RISCV_SYSCON_PLMT,	/* Platform Level Machine Timer (PLMT) */
 };
 
 #endif /* _ASM_SYSCON_H */

arch/riscv/lib/Makefile

@@ -12,6 +12,7 @@ obj-y	+= cache.o
 obj-$(CONFIG_RISCV_RDTIME) += rdtime.o
 obj-$(CONFIG_SIFIVE_CLINT) += sifive_clint.o
 obj-$(CONFIG_ANDES_PLIC) += andes_plic.o
+obj-$(CONFIG_ANDES_PLMT) += andes_plmt.o
 obj-y	+= interrupts.o
 obj-y	+= reset.o
 obj-$(CONFIG_SBI_IPI) += sbi_ipi.o

arch/riscv/lib/andes_plmt.c

@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2019, Rick Chen <rick@andestech.com>
+ *
+ * U-Boot syscon driver for Andes's Platform Level Machine Timer (PLMT).
+ * The PLMT block holds memory-mapped mtime register
+ * associated with timer tick.
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <regmap.h>
+#include <syscon.h>
+#include <asm/io.h>
+#include <asm/syscon.h>
+
+/* mtime register */
+#define MTIME_REG(base)			((ulong)(base))
+
+DECLARE_GLOBAL_DATA_PTR;
+
+#define PLMT_BASE_GET(void)						\
+	do {								\
+		long *ret;						\
+									\
+		if (!gd->arch.plmt) {					\
+			ret = syscon_get_first_range(RISCV_SYSCON_PLMT); \
+			if (IS_ERR(ret))				\
+				return PTR_ERR(ret);			\
+			gd->arch.plmt = ret;				\
+		}							\
+	} while (0)
+
+int riscv_get_time(u64 *time)
+{
+	PLMT_BASE_GET();
+
+	*time = readq((void __iomem *)MTIME_REG(gd->arch.plmt));
+
+	return 0;
+}
+
+static const struct udevice_id andes_plmt_ids[] = {
+	{ .compatible = "riscv,plmt0", .data = RISCV_SYSCON_PLMT },
+	{ }
+};
+
+U_BOOT_DRIVER(andes_plmt) = {
+	.name		= "andes_plmt",
+	.id		= UCLASS_SYSCON,
+	.of_match	= andes_plmt_ids,
+	.flags		= DM_FLAG_PRE_RELOC,
+};