RISC-V: Add mechanism to provide custom IPI operations

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>
Tested-by: Emil Renner Berhing <kernel@esmil.dk>
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/include/asm/clint.h

@@ -6,34 +6,9 @@
 #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 */

arch/riscv/include/asm/smp.h

@@ -15,6 +15,11 @@
 struct seq_file;
 extern unsigned long boot_cpu_hartid;
 
+struct riscv_ipi_ops {
+	void (*ipi_inject)(const struct cpumask *target);
+	void (*ipi_clear)(void);
+};
+
 #ifdef CONFIG_SMP
 /*
  * Mapping between linux logical cpu index and hartid.
@@ -40,6 +45,12 @@ 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);
 
+/* Set custom IPI operations */
+void riscv_set_ipi_ops(struct riscv_ipi_ops *ops);
+
+/* Clear IPI for current CPU */
+void riscv_clear_ipi(void);
+
 /* Secondary hart entry */
 asmlinkage void smp_callin(void);
 
@@ -81,6 +92,14 @@ static inline void riscv_cpuid_to_hartid_mask(const struct cpumask *in,
 	cpumask_set_cpu(boot_cpu_hartid, out);
 }
 
+static inline void riscv_set_ipi_ops(struct riscv_ipi_ops *ops)
+{
+}
+
+static inline void riscv_clear_ipi(void)
+{
+}
+
 #endif /* CONFIG_SMP */
 
 #if defined(CONFIG_HOTPLUG_CPU) && (CONFIG_SMP)

arch/riscv/kernel/clint.c

@@ -5,11 +5,11 @@
 
 #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>
-#include <asm/smp.h>
 
 /*
  * This is the layout used by the SiFive clint, which is also shared by the qemu
@@ -21,6 +21,24 @@
 
 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;
@@ -40,5 +58,6 @@ void clint_init_boot_cpu(void)
 	riscv_time_cmp = base + CLINT_TIME_CMP_OFF;
 	riscv_time_val = base + CLINT_TIME_VAL_OFF;
 
-	clint_clear_ipi(boot_cpu_hartid);
+	clint_clear_ipi();
+	riscv_set_ipi_ops(&clint_ipi_ops);
 }

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;
 }

arch/riscv/kernel/smp.c

@@ -86,9 +86,25 @@ 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();
@@ -96,33 +112,22 @@ 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");
 }
 
 #ifdef CONFIG_IRQ_WORK
@@ -140,7 +145,7 @@ void handle_IPI(struct pt_regs *regs)
 
 	irq_enter();
 
-	clear_ipi();
+	riscv_clear_ipi();
 
 	while (true) {
 		unsigned long ops;

arch/riscv/kernel/smpboot.c

@@ -147,8 +147,7 @@ asmlinkage __visible void smp_callin(void)
 	struct mm_struct *mm = &init_mm;
 	unsigned int curr_cpuid = smp_processor_id();
 
-	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);