RISC-V: Remove CLINT related code from timer and arch

Right now the RISC-V timer driver is convoluted to support:
1. Linux RISC-V S-mode (with MMU) where it will use TIME CSR for
   clocksource and SBI timer calls for clockevent device.
2. Linux RISC-V M-mode (without MMU) where it will use CLINT MMIO
   counter register for clocksource and CLINT MMIO compare register
   for clockevent device.

We now have a separate CLINT timer driver which also provide CLINT
based IPI operations so let's remove CLINT MMIO related code from
arch/riscv directory and RISC-V timer driver.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Tested-by: Emil Renner Berhing <kernel@esmil.dk>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/Kconfig

@@ -81,7 +81,7 @@ config RISCV
 	select PCI_DOMAINS_GENERIC if PCI
 	select PCI_MSI if PCI
 	select RISCV_INTC
-	select RISCV_TIMER
+	select RISCV_TIMER if RISCV_SBI
 	select SPARSEMEM_STATIC if 32BIT
 	select SPARSE_IRQ
 	select SYSCTL_EXCEPTION_TRACE

arch/riscv/Kconfig.socs

@@ -12,6 +12,7 @@ config SOC_SIFIVE
 
 config SOC_VIRT
 	bool "QEMU Virt Machine"
+	select CLINT_TIMER if RISCV_M_MODE
 	select POWER_RESET
 	select POWER_RESET_SYSCON
 	select POWER_RESET_SYSCON_POWEROFF
@@ -24,6 +25,7 @@ config SOC_VIRT
 config SOC_KENDRYTE
 	bool "Kendryte K210 SoC"
 	depends on !MMU
+	select CLINT_TIMER if RISCV_M_MODE
 	select SERIAL_SIFIVE if TTY
 	select SERIAL_SIFIVE_CONSOLE if TTY
 	select SIFIVE_PLIC

arch/riscv/configs/nommu_virt_defconfig

@@ -26,6 +26,7 @@ CONFIG_EXPERT=y
 CONFIG_SLOB=y
 # CONFIG_SLAB_MERGE_DEFAULT is not set
 # CONFIG_MMU is not set
+CONFIG_SOC_VIRT=y
 CONFIG_MAXPHYSMEM_2GB=y
 CONFIG_SMP=y
 CONFIG_CMDLINE="root=/dev/vda rw earlycon=uart8250,mmio,0x10000000,115200n8 console=ttyS0"
@@ -49,7 +50,6 @@ CONFIG_VIRTIO_BLK=y
 # CONFIG_SERIO is not set
 # CONFIG_LEGACY_PTYS is not set
 # CONFIG_LDISC_AUTOLOAD is not set
-# CONFIG_DEVMEM is not set
 CONFIG_SERIAL_8250=y
 # CONFIG_SERIAL_8250_DEPRECATED_OPTIONS is not set
 CONFIG_SERIAL_8250_CONSOLE=y
@@ -57,16 +57,13 @@ CONFIG_SERIAL_8250_NR_UARTS=1
 CONFIG_SERIAL_8250_RUNTIME_UARTS=1
 CONFIG_SERIAL_OF_PLATFORM=y
 # CONFIG_HW_RANDOM is not set
+# CONFIG_DEVMEM is not set
 # CONFIG_HWMON is not set
-# CONFIG_LCD_CLASS_DEVICE is not set
-# CONFIG_BACKLIGHT_CLASS_DEVICE is not set
 # CONFIG_VGA_CONSOLE is not set
 # CONFIG_HID is not set
 # CONFIG_USB_SUPPORT is not set
 CONFIG_VIRTIO_MMIO=y
 CONFIG_VIRTIO_MMIO_CMDLINE_DEVICES=y
-CONFIG_SIFIVE_PLIC=y
-# CONFIG_VALIDATE_FS_PARSER is not set
 CONFIG_EXT2_FS=y
 # CONFIG_DNOTIFY is not set
 # CONFIG_INOTIFY_USER is not set

arch/riscv/include/asm/clint.h

-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef _ASM_RISCV_CLINT_H
-#define _ASM_RISCV_CLINT_H 1
-
-#include <linux/io.h>
-#include <linux/smp.h>
-
-#ifdef CONFIG_RISCV_M_MODE
-void clint_init_boot_cpu(void);
-#else /* CONFIG_RISCV_M_MODE */
-#define clint_init_boot_cpu()	do { } while (0)
-#endif /* CONFIG_RISCV_M_MODE */
-
-#endif /* _ASM_RISCV_CLINT_H */

arch/riscv/include/asm/timex.h

@@ -7,41 +7,27 @@
 #define _ASM_RISCV_TIMEX_H
 
 #include <asm/csr.h>
-#include <asm/mmio.h>
 
 typedef unsigned long cycles_t;
 
-extern u64 __iomem *riscv_time_val;
-extern u64 __iomem *riscv_time_cmp;
-
-#ifdef CONFIG_64BIT
-#define mmio_get_cycles()	readq_relaxed(riscv_time_val)
-#else
-#define mmio_get_cycles()	readl_relaxed(riscv_time_val)
-#define mmio_get_cycles_hi()	readl_relaxed(((u32 *)riscv_time_val) + 1)
-#endif
-
 static inline cycles_t get_cycles(void)
 {
-	if (IS_ENABLED(CONFIG_RISCV_SBI))
-		return csr_read(CSR_TIME);
-	return mmio_get_cycles();
+	return csr_read(CSR_TIME);
 }
 #define get_cycles get_cycles
 
+static inline u32 get_cycles_hi(void)
+{
+	return csr_read(CSR_TIMEH);
+}
+#define get_cycles_hi get_cycles_hi
+
 #ifdef CONFIG_64BIT
 static inline u64 get_cycles64(void)
 {
 	return get_cycles();
 }
 #else /* CONFIG_64BIT */
-static inline u32 get_cycles_hi(void)
-{
-	if (IS_ENABLED(CONFIG_RISCV_SBI))
-		return csr_read(CSR_TIMEH);
-	return mmio_get_cycles_hi();
-}
-
 static inline u64 get_cycles64(void)
 {
 	u32 hi, lo;

arch/riscv/kernel/Makefile

@@ -31,7 +31,7 @@ obj-y	+= cacheinfo.o
 obj-y	+= patch.o
 obj-$(CONFIG_MMU) += vdso.o vdso/
 
-obj-$(CONFIG_RISCV_M_MODE)	+= clint.o traps_misaligned.o
+obj-$(CONFIG_RISCV_M_MODE)	+= traps_misaligned.o
 obj-$(CONFIG_FPU)		+= fpu.o
 obj-$(CONFIG_SMP)		+= smpboot.o
 obj-$(CONFIG_SMP)		+= smp.o

arch/riscv/kernel/clint.c

-// SPDX-License-Identifier: GPL-2.0
-/*
- * Copyright (c) 2019 Christoph Hellwig.
- */
-
-#include <linux/io.h>
-#include <linux/of_address.h>
-#include <linux/smp.h>
-#include <linux/types.h>
-#include <asm/clint.h>
-#include <asm/csr.h>
-#include <asm/timex.h>
-
-/*
- * This is the layout used by the SiFive clint, which is also shared by the qemu
- * virt platform, and the Kendryte KD210 at least.
- */
-#define CLINT_IPI_OFF		0
-#define CLINT_TIME_CMP_OFF	0x4000
-#define CLINT_TIME_VAL_OFF	0xbff8
-
-u32 __iomem *clint_ipi_base;
-
-static void clint_send_ipi(const struct cpumask *target)
-{
-	unsigned int cpu;
-
-	for_each_cpu(cpu, target)
-		writel(1, clint_ipi_base + cpuid_to_hartid_map(cpu));
-}
-
-static void clint_clear_ipi(void)
-{
-	writel(0, clint_ipi_base + cpuid_to_hartid_map(smp_processor_id()));
-}
-
-static struct riscv_ipi_ops clint_ipi_ops = {
-	.ipi_inject = clint_send_ipi,
-	.ipi_clear = clint_clear_ipi,
-};
-
-void clint_init_boot_cpu(void)
-{
-	struct device_node *np;
-	void __iomem *base;
-
-	np = of_find_compatible_node(NULL, NULL, "riscv,clint0");
-	if (!np) {
-		panic("clint not found");
-		return;
-	}
-
-	base = of_iomap(np, 0);
-	if (!base)
-		panic("could not map CLINT");
-
-	clint_ipi_base = base + CLINT_IPI_OFF;
-	riscv_time_cmp = base + CLINT_TIME_CMP_OFF;
-	riscv_time_val = base + CLINT_TIME_VAL_OFF;
-
-	clint_clear_ipi();
-	riscv_set_ipi_ops(&clint_ipi_ops);
-}

arch/riscv/kernel/setup.c

@@ -18,7 +18,6 @@
 #include <linux/swiotlb.h>
 #include <linux/smp.h>
 
-#include <asm/clint.h>
 #include <asm/cpu_ops.h>
 #include <asm/setup.h>
 #include <asm/sections.h>
@@ -79,7 +78,6 @@ void __init setup_arch(char **cmdline_p)
 #else
 	unflatten_device_tree();
 #endif
-	clint_init_boot_cpu();
 
 #ifdef CONFIG_SWIOTLB
 	swiotlb_init(1);

arch/riscv/kernel/smp.c

@@ -18,7 +18,6 @@
 #include <linux/delay.h>
 #include <linux/irq_work.h>
 
-#include <asm/clint.h>
 #include <asm/sbi.h>
 #include <asm/tlbflush.h>
 #include <asm/cacheflush.h>

arch/riscv/kernel/smpboot.c

@@ -24,7 +24,6 @@
 #include <linux/of.h>
 #include <linux/sched/task_stack.h>
 #include <linux/sched/mm.h>
-#include <asm/clint.h>
 #include <asm/cpu_ops.h>
 #include <asm/irq.h>
 #include <asm/mmu_context.h>

drivers/clocksource/Kconfig

@@ -653,9 +653,8 @@ config ATCPIT100_TIMER
 	  This option enables support for the Andestech ATCPIT100 timers.
 
 config RISCV_TIMER
-	bool "Timer for the RISC-V platform"
+	bool "Timer for the RISC-V platform" if COMPILE_TEST
 	depends on GENERIC_SCHED_CLOCK && RISCV
-	default y
 	select TIMER_PROBE
 	select TIMER_OF
 	help

drivers/clocksource/timer-riscv.c

@@ -19,26 +19,13 @@
 #include <linux/of_irq.h>
 #include <asm/smp.h>
 #include <asm/sbi.h>
-
-u64 __iomem *riscv_time_cmp;
-u64 __iomem *riscv_time_val;
-
-static inline void mmio_set_timer(u64 val)
-{
-	void __iomem *r;
-
-	r = riscv_time_cmp + cpuid_to_hartid_map(smp_processor_id());
-	writeq_relaxed(val, r);
-}
+#include <asm/timex.h>
 
 static int riscv_clock_next_event(unsigned long delta,
 		struct clock_event_device *ce)
 {
 	csr_set(CSR_IE, IE_TIE);
-	if (IS_ENABLED(CONFIG_RISCV_SBI))
-		sbi_set_timer(get_cycles64() + delta);
-	else
-		mmio_set_timer(get_cycles64() + delta);
+	sbi_set_timer(get_cycles64() + delta);
 	return 0;
 }