clocksource: timer-riscv: Don't enable/disable timer interrupt

Currently, we enable/disable timer interrupt at runtime to start/stop
timer events. This makes timer interrupt state go out-of-sync with
the Linux interrupt subsystem.

To address the above issue, we can stop a per-HART timer interrupt
by setting U64_MAX in timecmp CSR (or sbi_set_timer()) at the time
of handling timer interrupt.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Link: https://lore.kernel.org/r/20230710131902.1459180-2-apatel@ventanamicro.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
index da3071b387eb59f6c003fcd7e58062d114d5c54a..f2ea2b3d2d43e0327a71d570bb81f34964dd2bbe 100644 (file)
--- a/drivers/clocksource/timer-riscv.c
+++ b/drivers/clocksource/timer-riscv.c
@@ -22,6 +22,7 @@
 #include <linux/io-64-nonatomic-lo-hi.h>
 #include <linux/interrupt.h>
 #include <linux/of_irq.h>
+#include <linux/limits.h>
 #include <clocksource/timer-riscv.h>
 #include <asm/smp.h>
 #include <asm/hwcap.h>
@@ -31,12 +32,22 @@
 static DEFINE_STATIC_KEY_FALSE(riscv_sstc_available);
 static bool riscv_timer_cannot_wake_cpu;
 
+static void riscv_clock_event_stop(void)
+{
+       if (static_branch_likely(&riscv_sstc_available)) {
+               csr_write(CSR_STIMECMP, ULONG_MAX);
+               if (IS_ENABLED(CONFIG_32BIT))
+                       csr_write(CSR_STIMECMPH, ULONG_MAX);
+       } else {
+               sbi_set_timer(U64_MAX);
+       }
+}
+
 static int riscv_clock_next_event(unsigned long delta,
                struct clock_event_device *ce)
 {
        u64 next_tval = get_cycles64() + delta;
 
-       csr_set(CSR_IE, IE_TIE);
        if (static_branch_likely(&riscv_sstc_available)) {
 #if defined(CONFIG_32BIT)
                csr_write(CSR_STIMECMP, next_tval & 0xFFFFFFFF);
@@ -119,7 +130,7 @@ static irqreturn_t riscv_timer_interrupt(int irq, void *dev_id)
 {
        struct clock_event_device *evdev = this_cpu_ptr(&riscv_clock_event);
 
-       csr_clear(CSR_IE, IE_TIE);
+       riscv_clock_event_stop();
        evdev->event_handler(evdev);
 
        return IRQ_HANDLED;