stm32h7: add clock enable/disable callbacks

Change-Id: I4c135ba9cbed2c8e607c5f191bb9d82638f9b6b3

firmware/SOURCES

@@ -2019,6 +2019,7 @@ target/arm/rk27xx/ihifi2/audio-ihifi800.c
 target/arm/stm32/crt0-stm32h7.S
 target/arm/stm32/vectors-stm32h7.S
 target/arm/stm32/adc-stm32h7.c
+target/arm/stm32/clock-stm32h7.c
 target/arm/stm32/debug-stm32h7.c
 target/arm/stm32/gpio-stm32h7.c
 target/arm/stm32/i2c-stm32h7.c

firmware/target/arm/stm32/clock-stm32h7.c

@@ -0,0 +1,65 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2025 Aidan MacDonald
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+#include "clock-stm32h7.h"
+#include "mutex.h"
+#include "panic.h"
+#include <stdint.h>
+
+struct stm_clock_state
+{
+    struct mutex mutex;
+    uint8_t refcount[STM_NUM_CLOCKS];
+};
+
+static struct stm_clock_state stm_clocks;
+
+void stm_clock_init(void)
+{
+    mutex_init(&stm_clocks.mutex);
+
+    stm_target_clock_init();
+}
+
+void stm_clock_enable(enum stm_clock clock)
+{
+    mutex_lock(&stm_clocks.mutex);
+
+    if (stm_clocks.refcount[clock] == UINT8_MAX)
+        panicf("%s: clock %d overflow", __func__, (int)clock);
+
+    if (stm_clocks.refcount[clock]++ == 0)
+        stm_target_clock_enable(clock, true);
+
+    mutex_unlock(&stm_clocks.mutex);
+}
+
+void stm_clock_disable(enum stm_clock clock)
+{
+    mutex_lock(&stm_clocks.mutex);
+
+    if (stm_clocks.refcount[clock] == 0)
+        panicf("%s: clock %d underflow", __func__, (int)clock);
+
+    if (--stm_clocks.refcount[clock] == 0)
+        stm_target_clock_enable(clock, false);
+
+    mutex_unlock(&stm_clocks.mutex);
+}

firmware/target/arm/stm32/clock-stm32h7.h

@@ -22,6 +22,18 @@
 #define __CLOCK_STM32H7_H__
 
 #include "system.h"
+#include <stdbool.h>
+
+enum stm_clock
+{
+    STM_CLOCK_SPI1_KER,
+    STM_CLOCK_SPI2_KER,
+    STM_CLOCK_SPI3_KER,
+    STM_CLOCK_SPI4_KER,
+    STM_CLOCK_SPI5_KER,
+    STM_CLOCK_SPI6_KER,
+    STM_NUM_CLOCKS,
+};
 
 /*
  * Implemented by the target to initialize all oscillators,
@@ -30,4 +42,28 @@
  */
 void stm_target_clock_init(void) INIT_ATTR;
 
+/*
+ * Callback to be implemented by the target when the hardware
+ * clock needs to be turned on or off. Clocks are internally
+ * reference counted so only the first / last user will change
+ * the hardware state.
+ *
+ * Only clocks that are actually used need to be implemented,
+ * and unless otherwise noted it is allowed for enable/disable
+ * to be a no-op if the clock is always enabled.
+ */
+void stm_target_clock_enable(enum stm_clock clock, bool enable);
+
+/*
+ * Called from system_init(). Sets up internal book-keeping
+ * and then calls stm_target_clock_init().
+ */
+void stm_clock_init(void) INIT_ATTR;
+
+/*
+ * Enable or disable a clock. Not safe to call from an IRQ handler.
+ */
+void stm_clock_enable(enum stm_clock clock);
+void stm_clock_disable(enum stm_clock clock);
+
 #endif /* __CLOCK_STM32H7_H__ */

firmware/target/arm/stm32/system-stm32h7.c

@@ -69,7 +69,7 @@ void system_init(void)
     stm_enable_caches();
 
     /* Initialize system clocks */
-    stm_target_clock_init();
+    stm_clock_init();
 
     /* TODO: move this */
     systick_init(1000/HZ);