[debug] remove lib/debug and move to the top/ module

Most of the functions for this was declared in a top level lk/ include
space, so go ahead and move it there.

A few exceptions:
- Moved spin() over to platform/time.h and platform/time.c since the
function more logically belongs to platform/time.h.  Any users of
spin() will need to update their headers to include platform/time.h
instead.

- Renamed spin_cycles() to arm_cm_spin_cycles() and moved over into
arm/cm.h since it is currently defined in arch/arm-m and only used for
targets that implicitly are for arm-m.

app/mdebug/jtag.c

@@ -22,6 +22,7 @@
 #include <printf.h>
 
 #include <platform.h>
+#include <platform/time.h>
 #include <arch/arm.h>
 #include <kernel/thread.h>
 

app/tests/thread_tests.c

@@ -17,6 +17,7 @@
 #include <kernel/semaphore.h>
 #include <kernel/event.h>
 #include <platform.h>
+#include <platform/time.h>
 #include <arch/atomic.h>
 
 static int sleep_thread(void *arg) {

arch/arm/arm-m/include/arch/arm/cm.h

@@ -177,6 +177,8 @@ static inline bool arm_cm_is_preempt_triggered(void) {
     return SCB->ICSR & SCB_ICSR_PENDSVSET_Msk;
 }
 
+void arm_cm_spin_cycles(uint32_t cycles);
+
 /* systick */
 void arm_cm_systick_init(uint32_t mhz);
 

arch/arm/arm-m/spin_cycles.c

@@ -11,7 +11,7 @@
 __ALIGNED(8) __NAKED
 #if     (__CORTEX_M >= 0x03) || (CORTEX_SC >= 300)
 
-void spin_cycles(uint32_t cycles) {
+void arm_cm_spin_cycles(uint32_t cycles) {
     asm (
         /* 4 cycles per loop, subtract out 8 cycles for the overhead of the next
          * 4 instructions, plus the call into and return from the function.
@@ -48,7 +48,7 @@ void spin_cycles(uint32_t cycles) {
 
 #else
 /* Cortex-M0 & Cortex-M0+    */
-void spin_cycles(uint32_t cycles) {
+void arm_cm_spin_cycles(uint32_t cycles) {
     asm (
         /* 4 cycles per loop, subtract out 8 cycles for the overhead of the next
          * 4 instructions, plus the call into and return from the function.

dev/gpio_i2c/gpio_i2c.c

@@ -40,28 +40,28 @@ static gpio_i2c_state_t gpio_i2c_states[GPIO_I2C_BUS_COUNT];
  ******************************************************************************/
 static inline void send_start(const gpio_i2c_info_t *i) {
     gpio_config(i->sda, GPIO_OUTPUT);
-    spin_cycles(i->qcd);
+    arm_cm_spin_cycles(i->qcd);
     gpio_config(i->scl, GPIO_OUTPUT);
-    spin_cycles(i->hcd);
+    arm_cm_spin_cycles(i->hcd);
 }
 
 static inline void send_stop(const gpio_i2c_info_t *i) {
     gpio_config(i->sda, GPIO_OUTPUT);
     gpio_config(i->scl, GPIO_I2C_INPUT);
-    spin_cycles(i->qcd);
+    arm_cm_spin_cycles(i->qcd);
     gpio_config(i->sda, GPIO_I2C_INPUT);
 }
 
 static inline void send_restart(const gpio_i2c_info_t *i) {
     gpio_config(i->scl, GPIO_I2C_INPUT);
-    spin_cycles(i->qcd);
+    arm_cm_spin_cycles(i->qcd);
     send_start(i);
 }
 
 static inline void send_nack(const gpio_i2c_info_t *i) {
-    spin_cycles(i->hcd);
+    arm_cm_spin_cycles(i->hcd);
     gpio_config(i->scl, GPIO_I2C_INPUT);
-    spin_cycles(i->hcd);
+    arm_cm_spin_cycles(i->hcd);
     gpio_config(i->scl, GPIO_OUTPUT);
     gpio_config(i->sda, GPIO_I2C_INPUT);
 }
@@ -86,19 +86,19 @@ static inline bool send_byte(const gpio_i2c_info_t *i, uint32_t b) {
          * here in order to hit that timing, they are welcome to add a spin
          * right here.
          */
-        spin_cycles(i->hcd);
+        arm_cm_spin_cycles(i->hcd);
         gpio_config(i->scl, GPIO_I2C_INPUT);
-        spin_cycles(i->hcd);
+        arm_cm_spin_cycles(i->hcd);
         gpio_config(i->scl, GPIO_OUTPUT);
     }
 
     gpio_config(i->sda, GPIO_I2C_INPUT);
-    spin_cycles(i->hcd);
+    arm_cm_spin_cycles(i->hcd);
     gpio_config(i->scl, GPIO_I2C_INPUT);
-    spin_cycles(i->hcd);
+    arm_cm_spin_cycles(i->hcd);
     ret = (0 == gpio_get(i->sda));
     gpio_config(i->scl, GPIO_OUTPUT);
-    spin_cycles(i->hcd);
+    arm_cm_spin_cycles(i->hcd);
 
     return ret;
 }
@@ -108,16 +108,16 @@ static inline void recv_byte(const gpio_i2c_info_t *i, uint8_t *b) {
 
     for (size_t j = 0; j < 7; ++j) {
         gpio_config(i->scl, GPIO_I2C_INPUT);
-        spin_cycles(i->hcd);
+        arm_cm_spin_cycles(i->hcd);
         if (gpio_get(i->sda))
             tmp |= 1;
         tmp <<= 1;
         gpio_config(i->scl, GPIO_OUTPUT);
-        spin_cycles(i->hcd);
+        arm_cm_spin_cycles(i->hcd);
     }
 
     gpio_config(i->scl, GPIO_I2C_INPUT);
-    spin_cycles(i->hcd);
+    arm_cm_spin_cycles(i->hcd);
     if (gpio_get(i->sda))
         tmp |= 1;
     gpio_config(i->scl, GPIO_OUTPUT);

kernel/rules.mk

@@ -4,7 +4,6 @@ MODULE := $(LOCAL_DIR)
 
 MODULE_DEPS := \
 	lib/libc \
-	lib/debug \
 	lib/heap
 
 MODULE_SRCS := \

lib/debug/rules.mk

@@ -1,8 +0,0 @@
-LOCAL_DIR := $(GET_LOCAL_DIR)
-
-MODULE := $(LOCAL_DIR)
-
-MODULE_SRCS += \
-	$(LOCAL_DIR)/debug.c
-
-include make/module.mk

lib/debugcommands/rules.mk

@@ -3,7 +3,6 @@ LOCAL_DIR := $(GET_LOCAL_DIR)
 MODULE := $(LOCAL_DIR)
 
 MODULE_DEPS += \
-	lib/debug \
 	lib/console
 
 MODULE_SRCS += \

platform/include/platform/time.h

@@ -22,5 +22,8 @@ lk_time_t current_time(void);
 /* Time in units of microseconds */
 lk_bigtime_t current_time_hires(void);
 
+/* spin the cpu for a period of (short) time */
+void spin(uint32_t usecs);
+
 __END_CDECLS
 

platform/lpc43xx/init.c

@@ -44,7 +44,7 @@ void platform_early_init(void) {
     // Enable, HF=0 BYPASS=0
     writel(0, XTAL_OSC_CTRL);
     // Wait
-    spin_cycles(3000); // 250uS @ 12MHz
+    arm_cm_spin_cycles(3000); // 250uS @ 12MHz
 
     // PLL1: 12MHz -> N=(/2) -> M=(x32) -> P=(/2)   96MHz
     cfg = PLL1_CTRL_NSEL_2 | PLL1_CTRL_PSEL_1 | PLL1_CTRL_MSEL(32) |
@@ -56,7 +56,7 @@ void platform_early_init(void) {
 
     // when moving from < 90 MHz to > 110MHz, must spend 50uS
     // at 90-110MHz before shifting to high speeds
-    spin_cycles(4800); // 50uS @ 96MHz
+    arm_cm_spin_cycles(4800); // 50uS @ 96MHz
 
     // disable P divider  192MHz
     writel(cfg | PLL1_CTRL_DIRECT, PLL1_CTRL);

platform/rules.mk

@@ -6,7 +6,8 @@ MODULE := $(LOCAL_DIR)
 MODULE_SRCS += \
 	$(LOCAL_DIR)/debug.c \
 	$(LOCAL_DIR)/init.c \
-	$(LOCAL_DIR)/power.c
+	$(LOCAL_DIR)/power.c \
+	$(LOCAL_DIR)/time.c \
 
 MODULE_OPTIONS := extra_warnings
 

platform/stm32f7xx/sdram.c

@@ -41,6 +41,7 @@
 #include <dev/gpio.h>
 #include <platform/stm32.h>
 #include <platform/sdram.h>
+#include <platform/time.h>
 
 /*
  * sdram initialization sequence, taken from

platform/time.c

@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) 2025 Travis Geiselbrecht
+ *
+ * Use of this source code is governed by a MIT-style
+ * license that can be found in the LICENSE file or at
+ * https://opensource.org/licenses/MIT
+ */
+#include <platform/time.h>
+
+void spin(uint32_t usecs) {
+    lk_bigtime_t start = current_time_hires();
+
+    while ((current_time_hires() - start) < usecs)
+        ;
+}

top/debug.c

@@ -18,13 +18,6 @@
 #include <platform/debug.h>
 #include <kernel/spinlock.h>
 
-void spin(uint32_t usecs) {
-    lk_bigtime_t start = current_time_hires();
-
-    while ((current_time_hires() - start) < usecs)
-        ;
-}
-
 void panic(const char *fmt, ...) {
     printf("panic (caller %p): ", __GET_CALLER());
 

top/include/lk/debug.h

@@ -56,10 +56,4 @@ void panic(const char *fmt, ...) __PRINTFLIKE(1, 2) __NO_RETURN;
 #define PANIC_UNIMPLEMENTED panic("%s:%d unimplemented\n", __PRETTY_FUNCTION__, __LINE__)
 #define PANIC_UNIMPLEMENTED_MSG(x...) panic("%s:%d unimplemented: %s\n", __PRETTY_FUNCTION__, __LINE__, x)
 
-/* spin the cpu for a period of (short) time */
-void spin(uint32_t usecs);
-
-/* spin the cpu for a certain number of cpu cycles */
-void spin_cycles(uint32_t usecs);
-
 __END_CDECLS

top/rules.mk

@@ -11,6 +11,7 @@ MODULE_DEPS := \
 	target
 
 MODULE_SRCS := \
+	$(LOCAL_DIR)/debug.c \
 	$(LOCAL_DIR)/init.c \
 	$(LOCAL_DIR)/main.c \