From 22c5b3e1dc4e3cf7de3f73ebbf5b59542f207f4b Mon Sep 17 00:00:00 2001
From: Josh Rahm <joshuarahm@gmail.com>
Date: Sun, 17 Nov 2024 23:04:11 -0700
Subject: System clock is sort of working.

It appears the frequency divider does not work. I've followed the data
sheet, but no matter what I set the frequency divider to it appears to
not work. It's possible maybe the GPIO is using an un-divided clock, but
I'm not sure.

Also the 32khz clock does not work I think. It might be an issue with
the board. The waveform is jagged and looks awful.

But I can switch from the HSE to the PLL.
---
 include/clock.h  | 45 +++++++++++++++++++++++++++++++++++++++++++++
 include/system.h | 14 ++++++++++++++
 2 files changed, 59 insertions(+)
 create mode 100644 include/clock.h
 create mode 100644 include/system.h

(limited to 'include')

diff --git a/include/clock.h b/include/clock.h
new file mode 100644
index 0000000..42e2edd
--- /dev/null
+++ b/include/clock.h
@@ -0,0 +1,45 @@
+#pragma once
+
+#include <stdint.h>
+enum clock_selection {
+  CLOCK_SELECTION_PLL = 0,
+  CLOCK_SELECTION_LSE,
+  CLOCK_SELECTION_LSI,
+  CLOCK_SELECTION_HSE,
+};
+
+typedef struct {
+  enum clock_selection sel;
+
+  union {
+    /* Divisor for the PLL. If set to 0, the default value of 5 is used. */
+    uint8_t pll_clock_divisor;
+
+    /* Divisor for the HSE. If set to 0, the default value of 5 is used. */
+    uint8_t hse_clock_divisor;
+  };
+} clock_cfg_t;
+
+// Called when the system clock is changed.
+typedef struct {
+  void (*on_clk_change)(const clock_cfg_t* cfg);
+} clock_chg_evt_listener_t;
+
+/* Set the system clock configuration. */
+int set_system_clock(const clock_cfg_t* clk_cfg);
+
+/* Returns the clock configuration the system is currently in. */
+int get_system_clock(clock_cfg_t* out);
+
+/* Returns the frequency for the provided clock config.  */
+uint32_t get_clock_freq(const clock_cfg_t* clk_cfg);
+
+void configure_lse(void);
+
+#define on_system_clock_changed(name)                                          \
+  void on_system_clock_changed__##name(const clock_cfg_t*);             \
+  __attribute__((                                                              \
+      __section__(".clock_change_listeners"))) clock_chg_evt_listener_t name = \
+      ((clock_chg_evt_listener_t){.on_clk_change =                             \
+                                      on_system_clock_changed__##name});       \
+  void on_system_clock_changed__##name
diff --git a/include/system.h b/include/system.h
new file mode 100644
index 0000000..ca29ade
--- /dev/null
+++ b/include/system.h
@@ -0,0 +1,14 @@
+#pragma once
+
+#include <stdint.h>
+
+#define SAFE_ACCESS_SIG_REG (*((volatile uint32_t*)0x40001040))
+
+#define SAFE_ACCESS_1 0x57
+#define SAFE_ACCESS_2 0xA8
+
+inline static void enter_safe_mode()
+{
+  SAFE_ACCESS_SIG_REG = SAFE_ACCESS_1;
+  SAFE_ACCESS_SIG_REG = SAFE_ACCESS_2;
+}
-- 
cgit