[PATCH v2 0/5] Dedicated CLINT timer driver

[PATCH v2 0/5] Dedicated CLINT timer driver

[Anup Patel]

The current RISC-V timer driver is convoluted and implements two
distinct timers:
 1. S-mode timer: This is for Linux RISC-V S-mode with MMU. The
    clocksource is implemented using TIME CSR and clockevent device
    is implemented using SBI Timer calls.
 2. M-mode timer: This is for Linux RISC-V M-mode without MMU. The
    clocksource is implemented using CLINT MMIO time register and
    clockevent device is implemented using CLINT MMIO timecmp registers.

This patchset removes clint related code from RISC-V timer driver and
arch/riscv directory. Instead, the series adds a dedicated MMIO based
CLINT driver under drivers/clocksource directory which can be used by
Linux RISC-V M-mode (i.e NoMMU Linux RISC-V).

The patchset is based up Linux-5.8-rc2 and can be found at riscv_clint_v2
branch of: https://github.com/avpatel/linux.git

This series is tested on:
 1. QEMU RV64 virt machine using Linux RISC-V S-mode
 2. QEMU RV32 virt machine using Linux RISC-V S-mode
 3. QEMU RV64 virt machine using Linux RISC-V M-mode (i.e. NoMMU)

Changes since v1:
 - Rebased series on Linux-5.8-rc2
 - Added pr_warn() for case where ipi_ops not available in PATCH1
 - Updated ipi_inject() prototype to use "struct cpumask *" in PATCH1
 - Updated CLINT_TIMER kconfig option to depend on RISCV_M_MODE in PATCH4
 - Added riscv,clint0 compatible string in DT bindings document

Anup Patel (5):
  RISC-V: Add mechanism to provide custom IPI operations
  RISC-V: Remove CLINT related code
  clocksource/drivers/timer-riscv: Remove MMIO related stuff
  clocksource/drivers: Add CLINT timer driver
  dt-bindings: timer: Add CLINT bindings

 .../bindings/timer/sifive,clint.txt           |  34 +++
 arch/riscv/Kconfig                            |   2 +-
 arch/riscv/include/asm/clint.h                |  39 ---
 arch/riscv/include/asm/smp.h                  |  11 +
 arch/riscv/include/asm/timex.h                |  28 +--
 arch/riscv/kernel/Makefile                    |   2 +-
 arch/riscv/kernel/clint.c                     |  44 ----
 arch/riscv/kernel/sbi.c                       |  14 ++
 arch/riscv/kernel/setup.c                     |   2 -
 arch/riscv/kernel/smp.c                       |  44 ++--
 arch/riscv/kernel/smpboot.c                   |   4 +-
 drivers/clocksource/Kconfig                   |  12 +-
 drivers/clocksource/Makefile                  |   1 +
 drivers/clocksource/timer-clint.c             | 229 ++++++++++++++++++
 drivers/clocksource/timer-riscv.c             |  17 +-
 include/linux/cpuhotplug.h                    |   1 +
 16 files changed, 337 insertions(+), 147 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/timer/sifive,clint.txt
 delete mode 100644 arch/riscv/include/asm/clint.h
 delete mode 100644 arch/riscv/kernel/clint.c
 create mode 100644 drivers/clocksource/timer-clint.c

-- 
2.25.1


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[PATCH v2 1/5] RISC-V: Add mechanism to provide custom IPI operations

[Anup Patel]

We add mechanism to set custom IPI operations so that CLINT driver
from drivers directory can provide custom IPI operations.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
---
 arch/riscv/include/asm/smp.h | 11 +++++++++
 arch/riscv/kernel/sbi.c      | 14 ++++++++++++
 arch/riscv/kernel/smp.c      | 43 ++++++++++++++++++++----------------
 arch/riscv/kernel/smpboot.c  |  3 +--
 4 files changed, 50 insertions(+), 21 deletions(-)

diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h
index 40bb1c15a731..c6acd44767c1 100644
--- a/arch/riscv/include/asm/smp.h
+++ b/arch/riscv/include/asm/smp.h
@@ -40,6 +40,17 @@ void arch_send_call_function_single_ipi(int cpu);
 int riscv_hartid_to_cpuid(int hartid);
 void riscv_cpuid_to_hartid_mask(const struct cpumask *in, struct cpumask *out);
 
+struct riscv_ipi_ops {
+	void (*ipi_inject)(const struct cpumask *target);
+	void (*ipi_clear)(void);
+};
+
+/* Set custom IPI operations */
+void riscv_set_ipi_ops(struct riscv_ipi_ops *ops);
+
+/* Clear IPI for current CPU */
+void riscv_clear_ipi(void);
+
 /*
  * Obtains the hart ID of the currently executing task.  This relies on
  * THREAD_INFO_IN_TASK, but we define that unconditionally.
diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
index f383ef5672b2..226ccce0f9e0 100644
--- a/arch/riscv/kernel/sbi.c
+++ b/arch/riscv/kernel/sbi.c
@@ -547,6 +547,18 @@ static inline long sbi_get_firmware_version(void)
 	return __sbi_base_ecall(SBI_EXT_BASE_GET_IMP_VERSION);
 }
 
+static void sbi_send_cpumask_ipi(const struct cpumask *target)
+{
+	struct cpumask hartid_mask;
+
+	riscv_cpuid_to_hartid_mask(target, &hartid_mask);
+
+	sbi_send_ipi(cpumask_bits(&hartid_mask));
+}
+
+static struct riscv_ipi_ops sbi_ipi_ops = {
+	.ipi_inject = sbi_send_cpumask_ipi
+};
 
 int __init sbi_init(void)
 {
@@ -587,5 +599,7 @@ int __init sbi_init(void)
 		__sbi_rfence	= __sbi_rfence_v01;
 	}
 
+	riscv_set_ipi_ops(&sbi_ipi_ops);
+
 	return 0;
 }
diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index b1d4f452f843..8b85683ce203 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -84,9 +84,25 @@ static void ipi_stop(void)
 		wait_for_interrupt();
 }
 
+static struct riscv_ipi_ops *ipi_ops;
+
+void riscv_set_ipi_ops(struct riscv_ipi_ops *ops)
+{
+	ipi_ops = ops;
+}
+EXPORT_SYMBOL_GPL(riscv_set_ipi_ops);
+
+void riscv_clear_ipi(void)
+{
+	if (ipi_ops && ipi_ops->ipi_clear)
+		ipi_ops->ipi_clear();
+
+	csr_clear(CSR_IP, IE_SIE);
+}
+EXPORT_SYMBOL_GPL(riscv_clear_ipi);
+
 static void send_ipi_mask(const struct cpumask *mask, enum ipi_message_type op)
 {
-	struct cpumask hartid_mask;
 	int cpu;
 
 	smp_mb__before_atomic();
@@ -94,33 +110,22 @@ static void send_ipi_mask(const struct cpumask *mask, enum ipi_message_type op)
 		set_bit(op, &ipi_data[cpu].bits);
 	smp_mb__after_atomic();
 
-	riscv_cpuid_to_hartid_mask(mask, &hartid_mask);
-	if (IS_ENABLED(CONFIG_RISCV_SBI))
-		sbi_send_ipi(cpumask_bits(&hartid_mask));
+	if (ipi_ops && ipi_ops->ipi_inject)
+		ipi_ops->ipi_inject(mask);
 	else
-		clint_send_ipi_mask(mask);
+		pr_warn("SMP: IPI inject method not available\n");
 }
 
 static void send_ipi_single(int cpu, enum ipi_message_type op)
 {
-	int hartid = cpuid_to_hartid_map(cpu);
-
 	smp_mb__before_atomic();
 	set_bit(op, &ipi_data[cpu].bits);
 	smp_mb__after_atomic();
 
-	if (IS_ENABLED(CONFIG_RISCV_SBI))
-		sbi_send_ipi(cpumask_bits(cpumask_of(hartid)));
-	else
-		clint_send_ipi_single(hartid);
-}
-
-static inline void clear_ipi(void)
-{
-	if (IS_ENABLED(CONFIG_RISCV_SBI))
-		csr_clear(CSR_IP, IE_SIE);
+	if (ipi_ops && ipi_ops->ipi_inject)
+		ipi_ops->ipi_inject(cpumask_of(cpu));
 	else
-		clint_clear_ipi(cpuid_to_hartid_map(smp_processor_id()));
+		pr_warn("SMP: IPI inject method not available\n");
 }
 
 void handle_IPI(struct pt_regs *regs)
@@ -131,7 +136,7 @@ void handle_IPI(struct pt_regs *regs)
 
 	irq_enter();
 
-	clear_ipi();
+	riscv_clear_ipi();
 
 	while (true) {
 		unsigned long ops;
diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index 4e9922790f6e..5fe849791bf0 100644
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -147,8 +147,7 @@ asmlinkage __visible void smp_callin(void)
 {
 	struct mm_struct *mm = &init_mm;
 
-	if (!IS_ENABLED(CONFIG_RISCV_SBI))
-		clint_clear_ipi(cpuid_to_hartid_map(smp_processor_id()));
+	riscv_clear_ipi();
 
 	/* All kernel threads share the same mm context.  */
 	mmgrab(mm);
-- 
2.25.1


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[PATCH v2 2/5] RISC-V: Remove CLINT related code

[Anup Patel]

We will be having separate CLINT timer driver which will also
provide CLINT based IPI operations so let's remove CLINT related
code from arch/riscv directory.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
---
 arch/riscv/include/asm/clint.h | 39 ------------------------------
 arch/riscv/kernel/Makefile     |  2 +-
 arch/riscv/kernel/clint.c      | 44 ----------------------------------
 arch/riscv/kernel/setup.c      |  2 --
 arch/riscv/kernel/smp.c        |  1 -
 arch/riscv/kernel/smpboot.c    |  1 -
 6 files changed, 1 insertion(+), 88 deletions(-)
 delete mode 100644 arch/riscv/include/asm/clint.h
 delete mode 100644 arch/riscv/kernel/clint.c

diff --git a/arch/riscv/include/asm/clint.h b/arch/riscv/include/asm/clint.h
deleted file mode 100644
index a279b17a6aad..000000000000
--- a/arch/riscv/include/asm/clint.h
+++ /dev/null
@@ -1,39 +0,0 @@
-/* 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
-extern u32 __iomem *clint_ipi_base;
-
-void clint_init_boot_cpu(void);
-
-static inline void clint_send_ipi_single(unsigned long hartid)
-{
-	writel(1, clint_ipi_base + hartid);
-}
-
-static inline void clint_send_ipi_mask(const struct cpumask *mask)
-{
-	int cpu;
-
-	for_each_cpu(cpu, mask)
-		clint_send_ipi_single(cpuid_to_hartid_map(cpu));
-}
-
-static inline void clint_clear_ipi(unsigned long hartid)
-{
-	writel(0, clint_ipi_base + hartid);
-}
-#else /* CONFIG_RISCV_M_MODE */
-#define clint_init_boot_cpu()	do { } while (0)
-
-/* stubs to for code is only reachable under IS_ENABLED(CONFIG_RISCV_M_MODE): */
-void clint_send_ipi_single(unsigned long hartid);
-void clint_send_ipi_mask(const struct cpumask *hartid_mask);
-void clint_clear_ipi(unsigned long hartid);
-#endif /* CONFIG_RISCV_M_MODE */
-
-#endif /* _ASM_RISCV_CLINT_H */
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index b355cf485671..7edf15643146 100644
--- a/arch/riscv/kernel/Makefile
+++ b/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
diff --git a/arch/riscv/kernel/clint.c b/arch/riscv/kernel/clint.c
deleted file mode 100644
index 3647980d14c3..000000000000
--- a/arch/riscv/kernel/clint.c
+++ /dev/null
@@ -1,44 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * Copyright (c) 2019 Christoph Hellwig.
- */
-
-#include <linux/io.h>
-#include <linux/of_address.h>
-#include <linux/types.h>
-#include <asm/clint.h>
-#include <asm/csr.h>
-#include <asm/timex.h>
-#include <asm/smp.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;
-
-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(boot_cpu_hartid);
-}
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index f04373be54a6..2c6dd329312b 100644
--- a/arch/riscv/kernel/setup.c
+++ b/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);
diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index 8b85683ce203..07626be78c23 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -17,7 +17,6 @@
 #include <linux/seq_file.h>
 #include <linux/delay.h>
 
-#include <asm/clint.h>
 #include <asm/sbi.h>
 #include <asm/tlbflush.h>
 #include <asm/cacheflush.h>
diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index 5fe849791bf0..a6cfa9842d4b 100644
--- a/arch/riscv/kernel/smpboot.c
+++ b/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>
-- 
2.25.1


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[PATCH v2 3/5] clocksource/drivers/timer-riscv: Remove MMIO related stuff

[Anup Patel]

Right now the RISC-V timer 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.

This patch removes MMIO related stuff from RISC-V timer driver
so that we can have a separate CLINT timer driver.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
---
 arch/riscv/Kconfig                |  2 +-
 arch/riscv/include/asm/timex.h    | 28 +++++++---------------------
 drivers/clocksource/Kconfig       |  2 +-
 drivers/clocksource/timer-riscv.c | 17 ++---------------
 4 files changed, 11 insertions(+), 38 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 448a9952aa2f..868bbc4d0803 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -72,7 +72,7 @@ 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
diff --git a/arch/riscv/include/asm/timex.h b/arch/riscv/include/asm/timex.h
index bad2a7c2cda5..a3fb85d505d4 100644
--- a/arch/riscv/include/asm/timex.h
+++ b/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;
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 91418381fcd4..8c6a0f1274af 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -649,7 +649,7 @@ config ATCPIT100_TIMER
 
 config RISCV_TIMER
 	bool "Timer for the RISC-V platform"
-	depends on GENERIC_SCHED_CLOCK && RISCV
+	depends on GENERIC_SCHED_CLOCK && RISCV_SBI
 	default y
 	select TIMER_PROBE
 	select TIMER_OF
diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
index 9de1dabfb126..c51c5ed15aa7 100644
--- a/drivers/clocksource/timer-riscv.c
+++ b/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;
 }
 
-- 
2.25.1


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[PATCH v2 4/5] clocksource/drivers: Add CLINT timer driver

[Anup Patel]

The TIME CSR and SBI calls are not available in RISC-V M-mode so we
add CLINT driver for Linux RISC-V M-mode (i.e. RISC-V NoMMU kernel).

Signed-off-by: Anup Patel <anup.patel@wdc.com>
---
 drivers/clocksource/Kconfig       |  10 ++
 drivers/clocksource/Makefile      |   1 +
 drivers/clocksource/timer-clint.c | 229 ++++++++++++++++++++++++++++++
 include/linux/cpuhotplug.h        |   1 +
 4 files changed, 241 insertions(+)
 create mode 100644 drivers/clocksource/timer-clint.c

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 8c6a0f1274af..d3bf66123c4e 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -658,6 +658,16 @@ config RISCV_TIMER
 	  is accessed via both the SBI and the rdcycle instruction.  This is
 	  required for all RISC-V systems.
 
+config CLINT_TIMER
+	bool "Timer for the RISC-V platform"
+	depends on GENERIC_SCHED_CLOCK && RISCV_M_MODE
+	default y
+	select TIMER_PROBE
+	select TIMER_OF
+	help
+	  This option enables the CLINT timer for RISC-V systems. The CLINT
+	  driver is usually used for NoMMU RISC-V systems.
+
 config CSKY_MP_TIMER
 	bool "SMP Timer for the C-SKY platform" if COMPILE_TEST
 	depends on CSKY
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index bdda1a2e4097..18e700e703a0 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -87,6 +87,7 @@ obj-$(CONFIG_CLKSRC_ST_LPC)		+= clksrc_st_lpc.o
 obj-$(CONFIG_X86_NUMACHIP)		+= numachip.o
 obj-$(CONFIG_ATCPIT100_TIMER)		+= timer-atcpit100.o
 obj-$(CONFIG_RISCV_TIMER)		+= timer-riscv.o
+obj-$(CONFIG_CLINT_TIMER)		+= timer-clint.o
 obj-$(CONFIG_CSKY_MP_TIMER)		+= timer-mp-csky.o
 obj-$(CONFIG_GX6605S_TIMER)		+= timer-gx6605s.o
 obj-$(CONFIG_HYPERV_TIMER)		+= hyperv_timer.o
diff --git a/drivers/clocksource/timer-clint.c b/drivers/clocksource/timer-clint.c
new file mode 100644
index 000000000000..e5c36d49bfdd
--- /dev/null
+++ b/drivers/clocksource/timer-clint.c
@@ -0,0 +1,229 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020 Western Digital Corporation or its affiliates.
+ *
+ * Most of the M-mode (i.e. NoMMU) RISC-V systems usually have a
+ * CLINT MMIO timer device.
+ */
+
+#define pr_fmt(fmt) "clint: " fmt
+#include <linux/bitops.h>
+#include <linux/clocksource.h>
+#include <linux/clockchips.h>
+#include <linux/cpu.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/sched_clock.h>
+#include <linux/io-64-nonatomic-lo-hi.h>
+#include <linux/interrupt.h>
+#include <linux/of_irq.h>
+#include <linux/smp.h>
+
+#define CLINT_IPI_OFF		0
+#define CLINT_TIMER_CMP_OFF	0x4000
+#define CLINT_TIMER_VAL_OFF	0xbff8
+
+/* CLINT manages IPI and Timer for RISC-V M-mode  */
+static u32 __iomem *clint_ipi_base;
+static u64 __iomem *clint_timer_cmp;
+static u64 __iomem *clint_timer_val;
+static unsigned long clint_timer_freq;
+static unsigned int clint_timer_irq;
+
+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,
+};
+
+#ifdef CONFIG_64BIT
+#define clint_get_cycles()	readq_relaxed(clint_timer_val)
+#else
+#define clint_get_cycles()	readl_relaxed(clint_timer_val)
+#define clint_get_cycles_hi()	readl_relaxed(((u32 *)clint_timer_val) + 1)
+#endif
+
+#ifdef CONFIG_64BIT
+static u64 clint_get_cycles64(void)
+{
+	return clint_get_cycles();
+}
+#else /* CONFIG_64BIT */
+static u64 clint_get_cycles64(void)
+{
+	u32 hi, lo;
+
+	do {
+		hi = clint_get_cycles_hi();
+		lo = clint_get_cycles();
+	} while (hi != clint_get_cycles_hi());
+
+	return ((u64)hi << 32) | lo;
+}
+#endif /* CONFIG_64BIT */
+
+static int clint_clock_next_event(unsigned long delta,
+				   struct clock_event_device *ce)
+{
+	void __iomem *r = clint_timer_cmp +
+			  cpuid_to_hartid_map(smp_processor_id());
+
+	csr_set(CSR_IE, IE_TIE);
+	writeq_relaxed(clint_get_cycles64() + delta, r);
+	return 0;
+}
+
+static DEFINE_PER_CPU(struct clock_event_device, clint_clock_event) = {
+	.name			= "clint_clockevent",
+	.features		= CLOCK_EVT_FEAT_ONESHOT,
+	.rating		= 100,
+	.set_next_event	= clint_clock_next_event,
+};
+
+static u64 clint_rdtime(struct clocksource *cs)
+{
+	return readq_relaxed(clint_timer_val);
+}
+
+static u64 notrace clint_sched_clock(void)
+{
+	return readq_relaxed(clint_timer_val);
+}
+
+static struct clocksource clint_clocksource = {
+	.name		= "clint_clocksource",
+	.rating	= 300,
+	.mask		= CLOCKSOURCE_MASK(64),
+	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
+	.read		= clint_rdtime,
+};
+
+static int clint_timer_starting_cpu(unsigned int cpu)
+{
+	struct clock_event_device *ce = per_cpu_ptr(&clint_clock_event, cpu);
+
+	ce->cpumask = cpumask_of(cpu);
+	clockevents_config_and_register(ce, clint_timer_freq, 200, ULONG_MAX);
+
+	enable_percpu_irq(clint_timer_irq,
+			  irq_get_trigger_type(clint_timer_irq));
+	return 0;
+}
+
+static int clint_timer_dying_cpu(unsigned int cpu)
+{
+	disable_percpu_irq(clint_timer_irq);
+	return 0;
+}
+
+static irqreturn_t clint_timer_interrupt(int irq, void *dev_id)
+{
+	struct clock_event_device *evdev = this_cpu_ptr(&clint_clock_event);
+
+	csr_clear(CSR_IE, IE_TIE);
+	evdev->event_handler(evdev);
+
+	return IRQ_HANDLED;
+}
+
+static int __init clint_timer_init_dt(struct device_node *np)
+{
+	int rc;
+	u32 i, nr_irqs;
+	void __iomem *base;
+	struct of_phandle_args oirq;
+
+	/*
+	 * Ensure that CLINT device interrupts are either RV_IRQ_TIMER or
+	 * RV_IRQ_SOFT. If it's anything else then we ignore the device.
+	 */
+	nr_irqs = of_irq_count(np);
+	for (i = 0; i < nr_irqs; i++) {
+		if (of_irq_parse_one(np, i, &oirq)) {
+			pr_err("%pOFP: failed to parse irq %d.\n", np, i);
+			continue;
+		}
+
+		if ((oirq.args_count != 1) ||
+		    (oirq.args[0] != RV_IRQ_TIMER &&
+		     oirq.args[0] != RV_IRQ_SOFT)) {
+			pr_err("%pOFP: invalid irq %d (hwirq %d)\n",
+			       np, i, oirq.args[0]);
+			return -ENODEV;
+		}
+
+		/* Find parent irq domain and map timer irq */
+		if (!clint_timer_irq &&
+		    oirq.args[0] == RV_IRQ_TIMER &&
+		    irq_find_host(oirq.np))
+			clint_timer_irq = irq_of_parse_and_map(np, i);
+	}
+
+	/* If CLINT timer irq not found then fail */
+	if (!clint_timer_irq) {
+		pr_err("%pOFP: timer irq not found\n", np);
+		return -ENODEV;
+	}
+
+	base = of_iomap(np, 0);
+	if (!base) {
+		pr_err("%pOFP: could not map registers\n", np);
+		return -ENODEV;
+	}
+
+	clint_ipi_base = base + CLINT_IPI_OFF;
+	clint_timer_cmp = base + CLINT_TIMER_CMP_OFF;
+	clint_timer_val = base + CLINT_TIMER_VAL_OFF;
+	clint_timer_freq = riscv_timebase;
+
+	pr_info("%pOFP: timer running at %ld Hz\n", np, clint_timer_freq);
+
+	rc = clocksource_register_hz(&clint_clocksource, clint_timer_freq);
+	if (rc) {
+		iounmap(base);
+		pr_err("%pOFP: clocksource register failed [%d]\n", np, rc);
+		return rc;
+	}
+
+	sched_clock_register(clint_sched_clock, 64, clint_timer_freq);
+
+	rc = request_percpu_irq(clint_timer_irq, clint_timer_interrupt,
+				 "clint-timer", &clint_clock_event);
+	if (rc) {
+		iounmap(base);
+		pr_err("registering percpu irq failed [%d]\n", rc);
+		return rc;
+	}
+
+	rc = cpuhp_setup_state(CPUHP_AP_CLINT_TIMER_STARTING,
+				"clockevents/clint/timer:starting",
+				clint_timer_starting_cpu,
+				clint_timer_dying_cpu);
+	if (rc) {
+		free_irq(clint_timer_irq, &clint_clock_event);
+		iounmap(base);
+		pr_err("%pOFP: cpuhp setup state failed [%d]\n", np, rc);
+		return rc;
+	}
+
+	riscv_set_ipi_ops(&clint_ipi_ops);
+	clint_clear_ipi();
+
+	return 0;
+}
+
+TIMER_OF_DECLARE(clint_timer, "riscv,clint0", clint_timer_init_dt);
+TIMER_OF_DECLARE(clint_timer1, "sifive,clint-1.0.0", clint_timer_init_dt);
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 191772d4a4d7..1451f4625833 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -132,6 +132,7 @@ enum cpuhp_state {
 	CPUHP_AP_MIPS_GIC_TIMER_STARTING,
 	CPUHP_AP_ARC_TIMER_STARTING,
 	CPUHP_AP_RISCV_TIMER_STARTING,
+	CPUHP_AP_CLINT_TIMER_STARTING,
 	CPUHP_AP_CSKY_TIMER_STARTING,
 	CPUHP_AP_HYPERV_TIMER_STARTING,
 	CPUHP_AP_KVM_STARTING,
-- 
2.25.1


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[PATCH v2 5/5] dt-bindings: timer: Add CLINT bindings

[Anup Patel]

We add DT bindings documentation for CLINT device.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
---
 .../bindings/timer/sifive,clint.txt           | 34 +++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/timer/sifive,clint.txt

diff --git a/Documentation/devicetree/bindings/timer/sifive,clint.txt b/Documentation/devicetree/bindings/timer/sifive,clint.txt
new file mode 100644
index 000000000000..45b75347a7d5
--- /dev/null
+++ b/Documentation/devicetree/bindings/timer/sifive,clint.txt
@@ -0,0 +1,34 @@
+SiFive Core Local Interruptor (CLINT)
+-------------------------------------
+
+SiFive (and other RISC-V) SOCs include an implementation of the SiFive Core
+Local Interruptor (CLINT) for M-mode timer and inter-processor interrupts.
+
+It directly connects to the timer and inter-processor interrupt lines of
+various HARTs (or CPUs) so RISC-V per-HART (or per-CPU) local interrupt
+controller is the parent interrupt controller for CLINT device.
+
+The clock frequency of CLINT is specified via "timebase-frequency" DT
+property of "/cpus" DT node. The "timebase-frequency" DT property is
+described in: Documentation/devicetree/bindings/riscv/cpus.yaml
+
+Required properties:
+- compatible : should be "riscv,clint0" or "sifive,clint-1.0.0". A specific
+  string identifying the actual implementation can be added if implementation
+  specific worked arounds are needed.
+- reg : Should contain 1 register range (address and length).
+- interrupts-extended : Specifies which HARTs (or CPUs) are connected to
+  the CLINT.  Each node pointed to should be a riscv,cpu-intc node, which
+  has a riscv node as parent.
+
+Example:
+
+	clint@2000000 {
+		compatible = "sifive,clint-1.0.0", "sifive,fu540-c000-clint";
+		interrupts-extended = <
+			&cpu1-intc 3 &cpu1-intc 7
+			&cpu2-intc 3 &cpu2-intc 7
+			&cpu3-intc 3 &cpu3-intc 7
+			&cpu4-intc 3 &cpu4-intc 7>;
+		reg = <0x2000000 0x4000000>;
+	};
-- 
2.25.1


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Re: [PATCH v2 0/5] Dedicated CLINT timer driver

[Palmer Dabbelt]

On Sat, 27 Jun 2020 09:19:52 PDT (-0700), Anup Patel wrote:
> The current RISC-V timer driver is convoluted and implements two
> distinct timers:
>  1. S-mode timer: This is for Linux RISC-V S-mode with MMU. The
>     clocksource is implemented using TIME CSR and clockevent device
>     is implemented using SBI Timer calls.
>  2. M-mode timer: This is for Linux RISC-V M-mode without MMU. The
>     clocksource is implemented using CLINT MMIO time register and
>     clockevent device is implemented using CLINT MMIO timecmp registers.
>
> This patchset removes clint related code from RISC-V timer driver and
> arch/riscv directory. Instead, the series adds a dedicated MMIO based
> CLINT driver under drivers/clocksource directory which can be used by
> Linux RISC-V M-mode (i.e NoMMU Linux RISC-V).
>
> The patchset is based up Linux-5.8-rc2 and can be found at riscv_clint_v2
> branch of: https://github.com/avpatel/linux.git
>
> This series is tested on:
>  1. QEMU RV64 virt machine using Linux RISC-V S-mode
>  2. QEMU RV32 virt machine using Linux RISC-V S-mode
>  3. QEMU RV64 virt machine using Linux RISC-V M-mode (i.e. NoMMU)
>
> Changes since v1:
>  - Rebased series on Linux-5.8-rc2
>  - Added pr_warn() for case where ipi_ops not available in PATCH1
>  - Updated ipi_inject() prototype to use "struct cpumask *" in PATCH1
>  - Updated CLINT_TIMER kconfig option to depend on RISCV_M_MODE in PATCH4
>  - Added riscv,clint0 compatible string in DT bindings document
>
> Anup Patel (5):
>   RISC-V: Add mechanism to provide custom IPI operations
>   RISC-V: Remove CLINT related code
>   clocksource/drivers/timer-riscv: Remove MMIO related stuff
>   clocksource/drivers: Add CLINT timer driver
>   dt-bindings: timer: Add CLINT bindings

This all generally LGTM, though I haven't been through the code line-by-line
yet.  It touches a bunch of trees, so I'd prefer to have some Acks before
merging -- I'll dig through the RISC-V specific stuff, but the new CLINT driver
probhably deserves a look from one of the clocksource folks.

I think the only issue is that the port will be broken between patch 2 and 4,
as at that point we won't have an M-mode timer driver.  I think it shouldn't be
too much to just reorder these, LMK if you want to do it or you want me to.

Thanks!

>
>  .../bindings/timer/sifive,clint.txt           |  34 +++
>  arch/riscv/Kconfig                            |   2 +-
>  arch/riscv/include/asm/clint.h                |  39 ---
>  arch/riscv/include/asm/smp.h                  |  11 +
>  arch/riscv/include/asm/timex.h                |  28 +--
>  arch/riscv/kernel/Makefile                    |   2 +-
>  arch/riscv/kernel/clint.c                     |  44 ----
>  arch/riscv/kernel/sbi.c                       |  14 ++
>  arch/riscv/kernel/setup.c                     |   2 -
>  arch/riscv/kernel/smp.c                       |  44 ++--
>  arch/riscv/kernel/smpboot.c                   |   4 +-
>  drivers/clocksource/Kconfig                   |  12 +-
>  drivers/clocksource/Makefile                  |   1 +
>  drivers/clocksource/timer-clint.c             | 229 ++++++++++++++++++
>  drivers/clocksource/timer-riscv.c             |  17 +-
>  include/linux/cpuhotplug.h                    |   1 +
>  16 files changed, 337 insertions(+), 147 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/timer/sifive,clint.txt
>  delete mode 100644 arch/riscv/include/asm/clint.h
>  delete mode 100644 arch/riscv/kernel/clint.c
>  create mode 100644 drivers/clocksource/timer-clint.c

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Re: [PATCH v2 5/5] dt-bindings: timer: Add CLINT bindings

[Rob Herring]

On Sat, Jun 27, 2020 at 09:49:57PM +0530, Anup Patel wrote:
> We add DT bindings documentation for CLINT device.
> 
> Signed-off-by: Anup Patel <anup.patel@wdc.com>
> Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
> ---
>  .../bindings/timer/sifive,clint.txt           | 34 +++++++++++++++++++
>  1 file changed, 34 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/timer/sifive,clint.txt

Bindings should be in DT schema format now.

> 
> diff --git a/Documentation/devicetree/bindings/timer/sifive,clint.txt b/Documentation/devicetree/bindings/timer/sifive,clint.txt
> new file mode 100644
> index 000000000000..45b75347a7d5
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/timer/sifive,clint.txt
> @@ -0,0 +1,34 @@
> +SiFive Core Local Interruptor (CLINT)
> +-------------------------------------
> +
> +SiFive (and other RISC-V) SOCs include an implementation of the SiFive Core
> +Local Interruptor (CLINT) for M-mode timer and inter-processor interrupts.
> +
> +It directly connects to the timer and inter-processor interrupt lines of
> +various HARTs (or CPUs) so RISC-V per-HART (or per-CPU) local interrupt
> +controller is the parent interrupt controller for CLINT device.
> +
> +The clock frequency of CLINT is specified via "timebase-frequency" DT
> +property of "/cpus" DT node. The "timebase-frequency" DT property is
> +described in: Documentation/devicetree/bindings/riscv/cpus.yaml
> +
> +Required properties:
> +- compatible : should be "riscv,clint0" or "sifive,clint-1.0.0". A specific

A new versioning scheme from SiFive? To review, we don't do version 
numbers unless there's a well defined and documented scheme. IOW, one 
that's not s/w folks just making up v1, v2, v3, etc.

> +  string identifying the actual implementation can be added if implementation
> +  specific worked arounds are needed.
> +- reg : Should contain 1 register range (address and length).
> +- interrupts-extended : Specifies which HARTs (or CPUs) are connected to
> +  the CLINT.  Each node pointed to should be a riscv,cpu-intc node, which
> +  has a riscv node as parent.
> +
> +Example:
> +
> +	clint@2000000 {
> +		compatible = "sifive,clint-1.0.0", "sifive,fu540-c000-clint";

Doesn't match the binding.

> +		interrupts-extended = <
> +			&cpu1-intc 3 &cpu1-intc 7
> +			&cpu2-intc 3 &cpu2-intc 7
> +			&cpu3-intc 3 &cpu3-intc 7
> +			&cpu4-intc 3 &cpu4-intc 7>;
> +		reg = <0x2000000 0x4000000>;
> +	};
> -- 
> 2.25.1
> 

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Re: [PATCH v2 5/5] dt-bindings: timer: Add CLINT bindings

[Anup Patel]

On Tue, Jul 14, 2020 at 8:07 AM Rob Herring <robh@kernel.org> wrote:
>
> On Sat, Jun 27, 2020 at 09:49:57PM +0530, Anup Patel wrote:
> > We add DT bindings documentation for CLINT device.
> >
> > Signed-off-by: Anup Patel <anup.patel@wdc.com>
> > Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
> > ---
> >  .../bindings/timer/sifive,clint.txt           | 34 +++++++++++++++++++
> >  1 file changed, 34 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/timer/sifive,clint.txt
>
> Bindings should be in DT schema format now.

Okay, will update.

>
> >
> > diff --git a/Documentation/devicetree/bindings/timer/sifive,clint.txt b/Documentation/devicetree/bindings/timer/sifive,clint.txt
> > new file mode 100644
> > index 000000000000..45b75347a7d5
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/timer/sifive,clint.txt
> > @@ -0,0 +1,34 @@
> > +SiFive Core Local Interruptor (CLINT)
> > +-------------------------------------
> > +
> > +SiFive (and other RISC-V) SOCs include an implementation of the SiFive Core
> > +Local Interruptor (CLINT) for M-mode timer and inter-processor interrupts.
> > +
> > +It directly connects to the timer and inter-processor interrupt lines of
> > +various HARTs (or CPUs) so RISC-V per-HART (or per-CPU) local interrupt
> > +controller is the parent interrupt controller for CLINT device.
> > +
> > +The clock frequency of CLINT is specified via "timebase-frequency" DT
> > +property of "/cpus" DT node. The "timebase-frequency" DT property is
> > +described in: Documentation/devicetree/bindings/riscv/cpus.yaml
> > +
> > +Required properties:
> > +- compatible : should be "riscv,clint0" or "sifive,clint-1.0.0". A specific
>
> A new versioning scheme from SiFive? To review, we don't do version
> numbers unless there's a well defined and documented scheme. IOW, one
> that's not s/w folks just making up v1, v2, v3, etc.

The "riscv,clint0" is already used by various RISC-V systems (including QEMU).

The "sifive,clint-1.0.0" is for being consistent with the PLIC
versioning scheme.

There is no clear documentation of CLINT versioning scheme. I think it's best
to just drop "sifive,clint-1.0.0" . Agree ??

>
> > +  string identifying the actual implementation can be added if implementation
> > +  specific worked arounds are needed.
> > +- reg : Should contain 1 register range (address and length).
> > +- interrupts-extended : Specifies which HARTs (or CPUs) are connected to
> > +  the CLINT.  Each node pointed to should be a riscv,cpu-intc node, which
> > +  has a riscv node as parent.
> > +
> > +Example:
> > +
> > +     clint@2000000 {
> > +             compatible = "sifive,clint-1.0.0", "sifive,fu540-c000-clint";
>
> Doesn't match the binding.

Okay, will update.

>
> > +             interrupts-extended = <
> > +                     &cpu1-intc 3 &cpu1-intc 7
> > +                     &cpu2-intc 3 &cpu2-intc 7
> > +                     &cpu3-intc 3 &cpu3-intc 7
> > +                     &cpu4-intc 3 &cpu4-intc 7>;
> > +             reg = <0x2000000 0x4000000>;
> > +     };
> > --
> > 2.25.1
> >

Regards,
Anup

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Re: [PATCH v2 0/5] Dedicated CLINT timer driver

[Anup Patel]

On Tue, Jul 14, 2020 at 4:32 AM Palmer Dabbelt <palmer@dabbelt.com> wrote:
>
> On Sat, 27 Jun 2020 09:19:52 PDT (-0700), Anup Patel wrote:
> > The current RISC-V timer driver is convoluted and implements two
> > distinct timers:
> >  1. S-mode timer: This is for Linux RISC-V S-mode with MMU. The
> >     clocksource is implemented using TIME CSR and clockevent device
> >     is implemented using SBI Timer calls.
> >  2. M-mode timer: This is for Linux RISC-V M-mode without MMU. The
> >     clocksource is implemented using CLINT MMIO time register and
> >     clockevent device is implemented using CLINT MMIO timecmp registers.
> >
> > This patchset removes clint related code from RISC-V timer driver and
> > arch/riscv directory. Instead, the series adds a dedicated MMIO based
> > CLINT driver under drivers/clocksource directory which can be used by
> > Linux RISC-V M-mode (i.e NoMMU Linux RISC-V).
> >
> > The patchset is based up Linux-5.8-rc2 and can be found at riscv_clint_v2
> > branch of: https://github.com/avpatel/linux.git
> >
> > This series is tested on:
> >  1. QEMU RV64 virt machine using Linux RISC-V S-mode
> >  2. QEMU RV32 virt machine using Linux RISC-V S-mode
> >  3. QEMU RV64 virt machine using Linux RISC-V M-mode (i.e. NoMMU)
> >
> > Changes since v1:
> >  - Rebased series on Linux-5.8-rc2
> >  - Added pr_warn() for case where ipi_ops not available in PATCH1
> >  - Updated ipi_inject() prototype to use "struct cpumask *" in PATCH1
> >  - Updated CLINT_TIMER kconfig option to depend on RISCV_M_MODE in PATCH4
> >  - Added riscv,clint0 compatible string in DT bindings document
> >
> > Anup Patel (5):
> >   RISC-V: Add mechanism to provide custom IPI operations
> >   RISC-V: Remove CLINT related code
> >   clocksource/drivers/timer-riscv: Remove MMIO related stuff
> >   clocksource/drivers: Add CLINT timer driver
> >   dt-bindings: timer: Add CLINT bindings
>
> This all generally LGTM, though I haven't been through the code line-by-line
> yet.  It touches a bunch of trees, so I'd prefer to have some Acks before
> merging -- I'll dig through the RISC-V specific stuff, but the new CLINT driver
> probhably deserves a look from one of the clocksource folks.
>
> I think the only issue is that the port will be broken between patch 2 and 4,
> as at that point we won't have an M-mode timer driver.  I think it shouldn't be
> too much to just reorder these, LMK if you want to do it or you want me to.

Okay, I will try your suggestion to reorder patches. There is another minor
build issue reported by test bots which I will fix as well.

I will send v3 in a couple of days before end-of-week.

Regards,
Anup

>
> Thanks!
>
> >
> >  .../bindings/timer/sifive,clint.txt           |  34 +++
> >  arch/riscv/Kconfig                            |   2 +-
> >  arch/riscv/include/asm/clint.h                |  39 ---
> >  arch/riscv/include/asm/smp.h                  |  11 +
> >  arch/riscv/include/asm/timex.h                |  28 +--
> >  arch/riscv/kernel/Makefile                    |   2 +-
> >  arch/riscv/kernel/clint.c                     |  44 ----
> >  arch/riscv/kernel/sbi.c                       |  14 ++
> >  arch/riscv/kernel/setup.c                     |   2 -
> >  arch/riscv/kernel/smp.c                       |  44 ++--
> >  arch/riscv/kernel/smpboot.c                   |   4 +-
> >  drivers/clocksource/Kconfig                   |  12 +-
> >  drivers/clocksource/Makefile                  |   1 +
> >  drivers/clocksource/timer-clint.c             | 229 ++++++++++++++++++
> >  drivers/clocksource/timer-riscv.c             |  17 +-
> >  include/linux/cpuhotplug.h                    |   1 +
> >  16 files changed, 337 insertions(+), 147 deletions(-)
> >  create mode 100644 Documentation/devicetree/bindings/timer/sifive,clint.txt
> >  delete mode 100644 arch/riscv/include/asm/clint.h
> >  delete mode 100644 arch/riscv/kernel/clint.c
> >  create mode 100644 drivers/clocksource/timer-clint.c

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Re: [PATCH v2 5/5] dt-bindings: timer: Add CLINT bindings

[Rob Herring]

On Mon, Jul 13, 2020 at 9:47 PM Anup Patel <anup@brainfault.org> wrote:
>
> On Tue, Jul 14, 2020 at 8:07 AM Rob Herring <robh@kernel.org> wrote:
> >
> > On Sat, Jun 27, 2020 at 09:49:57PM +0530, Anup Patel wrote:
> > > We add DT bindings documentation for CLINT device.
> > >
> > > Signed-off-by: Anup Patel <anup.patel@wdc.com>
> > > Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
> > > ---
> > >  .../bindings/timer/sifive,clint.txt           | 34 +++++++++++++++++++
> > >  1 file changed, 34 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/timer/sifive,clint.txt
> >
> > Bindings should be in DT schema format now.
>
> Okay, will update.
>
> >
> > >
> > > diff --git a/Documentation/devicetree/bindings/timer/sifive,clint.txt b/Documentation/devicetree/bindings/timer/sifive,clint.txt
> > > new file mode 100644
> > > index 000000000000..45b75347a7d5
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/timer/sifive,clint.txt
> > > @@ -0,0 +1,34 @@
> > > +SiFive Core Local Interruptor (CLINT)
> > > +-------------------------------------
> > > +
> > > +SiFive (and other RISC-V) SOCs include an implementation of the SiFive Core
> > > +Local Interruptor (CLINT) for M-mode timer and inter-processor interrupts.
> > > +
> > > +It directly connects to the timer and inter-processor interrupt lines of
> > > +various HARTs (or CPUs) so RISC-V per-HART (or per-CPU) local interrupt
> > > +controller is the parent interrupt controller for CLINT device.
> > > +
> > > +The clock frequency of CLINT is specified via "timebase-frequency" DT
> > > +property of "/cpus" DT node. The "timebase-frequency" DT property is
> > > +described in: Documentation/devicetree/bindings/riscv/cpus.yaml
> > > +
> > > +Required properties:
> > > +- compatible : should be "riscv,clint0" or "sifive,clint-1.0.0". A specific
> >
> > A new versioning scheme from SiFive? To review, we don't do version
> > numbers unless there's a well defined and documented scheme. IOW, one
> > that's not s/w folks just making up v1, v2, v3, etc.
>
> The "riscv,clint0" is already used by various RISC-V systems (including QEMU).

Not my problem that undocumented bindings are being used.

> The "sifive,clint-1.0.0" is for being consistent with the PLIC
> versioning scheme.

Where is that documented? This is what I expect you to be following or
updating to match:

Documentation/devicetree/bindings/sifive/sifive-blocks-ip-versioning.txt

>
> There is no clear documentation of CLINT versioning scheme. I think it's best
> to just drop "sifive,clint-1.0.0" . Agree ??

No, because then you are left with a very generic compatible string.
You need something specific enough to handle any implementation
features/quirks/bugs without needing a DT update. Typically, this
means a per SoC compatible string for a block as even the same IP
version can have different integration quirks.

Rob

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