RISC-V: Show IPI stats

This patch provides arch_show_interrupts() implementation to
show IPI stats via /proc/interrupts.

Now the contents of /proc/interrupts" will look like below:
           CPU0       CPU1       CPU2       CPU3
  8:         17          7          6         14  SiFive PLIC   8  virtio0
 10:         10         10          9         11  SiFive PLIC  10  ttyS0
IPI0:       170        673        251         79  Rescheduling interrupts
IPI1:         1         12         27          1  Function call interrupts

Signed-off-by: Anup Patel <anup@brainfault.org>
[Atish - Fixed checkpatch errors]
Signed-off-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Palmer Dabbelt <palmer@sifive.com>

Changes since v2:
 - Remove use of IPI_CALL_WAKEUP because it's being removed

Changes since v1:
 - Add stub inline show_ipi_stats() function for !CONFIG_SMP
 - Make ipi_names[] dynamically sized at compile time
 - Minor beautification of ipi_names[] using tabs

Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

3 files changed, 49 insertions, 7 deletions

diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h
index 47fd61dfc897..41aa73b476f4 100644
--- a/arch/riscv/include/asm/smp.h
+++ b/arch/riscv/include/asm/smp.h
@@ -25,8 +25,13 @@
 extern unsigned long __cpuid_to_hartid_map[NR_CPUS];
 #define cpuid_to_hartid_map(cpu)    __cpuid_to_hartid_map[cpu]
 
+struct seq_file;
+
 #ifdef CONFIG_SMP
 
+/* print IPI stats */
+void show_ipi_stats(struct seq_file *p, int prec);
+
 /* SMP initialization hook for setup_arch */
 void __init setup_smp(void);
 
@@ -47,6 +52,10 @@ void riscv_cpuid_to_hartid_mask(const struct cpumask *in, struct cpumask *out);
 
 #else
 
+static inline void show_ipi_stats(struct seq_file *p, int prec)
+{
+}
+
 static inline int riscv_hartid_to_cpuid(int hartid)
 {
         return 0;
diff --git a/arch/riscv/kernel/irq.c b/arch/riscv/kernel/irq.c
index ca4593317e45..48e6b7db83a1 100644
--- a/arch/riscv/kernel/irq.c
+++ b/arch/riscv/kernel/irq.c
@@ -8,6 +8,8 @@
 #include <linux/interrupt.h>
 #include <linux/irqchip.h>
 #include <linux/irqdomain.h>
+#include <linux/seq_file.h>
+#include <asm/smp.h>
 
 /*
  * Possible interrupt causes:
@@ -24,6 +26,12 @@
  */
 #define INTERRUPT_CAUSE_FLAG    (1UL << (__riscv_xlen - 1))
 
+int arch_show_interrupts(struct seq_file *p, int prec)
+{
+        show_ipi_stats(p, prec);
+        return 0;
+}
+
 asmlinkage void __irq_entry do_IRQ(struct pt_regs *regs)
 {
         struct pt_regs *old_regs = set_irq_regs(regs);
diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index 4eac0094f47e..57b1383e5ef7 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -22,22 +22,24 @@
 #include <linux/interrupt.h>
 #include <linux/smp.h>
 #include <linux/sched.h>
+#include <linux/seq_file.h>
 
 #include <asm/sbi.h>
 #include <asm/tlbflush.h>
 #include <asm/cacheflush.h>
 
-/* A collection of single bit ipi messages.  */
-static struct {
-        unsigned long bits ____cacheline_aligned;
-} ipi_data[NR_CPUS] __cacheline_aligned;
-
 enum ipi_message_type {
         IPI_RESCHEDULE,
         IPI_CALL_FUNC,
         IPI_MAX
 };
 
+/* A collection of single bit ipi messages.  */
+static struct {
+        unsigned long stats[IPI_MAX] ____cacheline_aligned;
+        unsigned long bits ____cacheline_aligned;
+} ipi_data[NR_CPUS] __cacheline_aligned;
+
 int riscv_hartid_to_cpuid(int hartid)
 {
         int i = -1;
@@ -67,6 +69,7 @@ int setup_profiling_timer(unsigned int multiplier)
 void riscv_software_interrupt(void)
 {
         unsigned long *pending_ipis = &ipi_data[smp_processor_id()].bits;
+        unsigned long *stats = ipi_data[smp_processor_id()].stats;
 
         /* Clear pending IPI */
         csr_clear(sip, SIE_SSIE);
@@ -81,11 +84,15 @@ void riscv_software_interrupt(void)
                 if (ops == 0)
                         return;
 
-                if (ops & (1 << IPI_RESCHEDULE))
+                if (ops & (1 << IPI_RESCHEDULE)) {
+                        stats[IPI_RESCHEDULE]++;
                         scheduler_ipi();
+                }
 
-                if (ops & (1 << IPI_CALL_FUNC))
+                if (ops & (1 << IPI_CALL_FUNC)) {
+                        stats[IPI_CALL_FUNC]++;
                         generic_smp_call_function_interrupt();
+                }
 
                 BUG_ON((ops >> IPI_MAX) != 0);
 
@@ -111,6 +118,24 @@ send_ipi_message(const struct cpumask *to_whom, enum ipi_message_type operation)
         sbi_send_ipi(cpumask_bits(&hartid_mask));
 }
 
+static const char * const ipi_names[] = {
+        [IPI_RESCHEDULE]        = "Rescheduling interrupts",
+        [IPI_CALL_FUNC]         = "Function call interrupts",
+};
+
+void show_ipi_stats(struct seq_file *p, int prec)
+{
+        unsigned int cpu, i;
+
+        for (i = 0; i < IPI_MAX; i++) {
+                seq_printf(p, "%*s%u:%s", prec - 1, "IPI", i,
+                           prec >= 4 ? " " : "");
+                for_each_online_cpu(cpu)
+                        seq_printf(p, "%10lu ", ipi_data[cpu].stats[i]);
+                seq_printf(p, " %s\n", ipi_names[i]);
+        }
+}
+
 void arch_send_call_function_ipi_mask(struct cpumask *mask)
 {
         send_ipi_message(mask, IPI_CALL_FUNC);