rp2/mphalport: Implement mp_hal_ticks_cpu for RISCV using mcycle.

dpgeorge · dpgeorge · commit bf79bfa9cbb5 · 2024-08-09T01:23:07.000+10:00
Signed-off-by: Damien George &lt;damien@micropython.org&gt;
diff --git a/ports/rp2/mphalport.c b/ports/rp2/mphalport.c
@@ -125,6 +125,17 @@ mp_uint_t mp_hal_stdout_tx_strn(const char *str, mp_uint_t len) {
     return did_write ? ret : 0;
 }
 
+#if PICO_RISCV
+__attribute__((naked)) mp_uint_t mp_hal_ticks_cpu(void) {
+    __asm volatile (
+        "li a0, 4\n" // mask value to uninhibit mcycle counter
+        "csrw mcountinhibit, a0\n" // uninhibit mcycle counter
+        "csrr a0, mcycle\n" // get mcycle counter
+        "ret\n"
+    );
+}
+#endif
+
 void mp_hal_delay_us(mp_uint_t us) {
     // Avoid calling sleep_us() and invoking the alarm pool by splitting long
     // sleeps into an optional longer sleep and a shorter busy-wait
diff --git a/ports/rp2/mphalport.h b/ports/rp2/mphalport.h
@@ -92,11 +92,15 @@ static inline mp_uint_t mp_hal_ticks_ms(void) {
     return to_ms_since_boot(get_absolute_time());
 }
 
+#if PICO_ARM
 static inline mp_uint_t mp_hal_ticks_cpu(void) {
     // ticks_cpu() is defined as using the highest-resolution timing source
     // in the system. This is usually a CPU clock, but doesn't have to be.
     return time_us_32();
 }
+#elif PICO_RISCV
+mp_uint_t mp_hal_ticks_cpu(void);
+#endif
 
 static inline mp_uint_t mp_hal_get_cpu_freq(void) {
     return clock_get_hz(clk_sys);

Original file line number	Diff line number	Diff line change
`@@ -92,11 +92,15 @@ static inline mp_uint_t mp_hal_ticks_ms(void) {`
`92`	`92`	`return to_ms_since_boot(get_absolute_time());`
`93`	`93`	`}`
`94`	`94`
	`95`	`+#if PICO_ARM`
`95`	`96`	`static inline mp_uint_t mp_hal_ticks_cpu(void) {`
`96`	`97`	`// ticks_cpu() is defined as using the highest-resolution timing source`
`97`	`98`	`// in the system. This is usually a CPU clock, but doesn't have to be.`
`98`	`99`	`return time_us_32();`
`99`	`100`	`}`
	`101`	`+#elif PICO_RISCV`
	`102`	`+mp_uint_t mp_hal_ticks_cpu(void);`
	`103`	`+#endif`
`100`	`104`
`101`	`105`	`static inline mp_uint_t mp_hal_get_cpu_freq(void) {`
`102`	`106`	`return clock_get_hz(clk_sys);`