Port bare metal Arctic Tern LPC clock setup to Zephyr firmware

kestrel/src/aquila.h

-// © 2020 Raptor Engineering, LLC
+// © 2020-2022 Raptor Engineering, LLC
 //
 // Released under the terms of the GPL v3
 // See the LICENSE file for full details
@@ -141,6 +141,11 @@
 #define AQUILA_LPC_VUART_WFIFO_FULL_MASK     0x1
 #define AQUILA_LPC_VUART_WFIFO_FULL_SHIFT    24
 
+#define AQUILA_LPC_CLOCK_VALID_MASK    0x1
+#define AQUILA_LPC_CLOCK_VALID_SHIFT   24
+#define AQUILA_LPC_CLK_PLL_RESET_MASK  0x1
+#define AQUILA_LPC_CLK_PLL_RESET_SHIFT 31
+
 #define AQUILA_EV_MASTER_IRQ 0x1
 
 static inline uint32_t read_aquila_register(unsigned long base_address, uint8_t reg)

kestrel/src/kestrel.c

@@ -2319,6 +2319,7 @@ int power_on_chassis(int has_lock)
     int cpu_count = 1;
     int i2c_read_retcode;
     uint8_t byte;
+    uint32_t dword;
 
     if (!has_lock) {
         if (k_sem_take(&chassis_control_semaphore, K_MSEC(10)) != 0) {
@@ -2426,6 +2427,36 @@ int power_on_chassis(int has_lock)
         return -5;
     }
 
+    // Force the LPC clock PLL into reset, if present
+    // If no PLL is present, this operation does nothing
+    dword = read_aquila_register(HOSTLPCSLAVE_BASE, AQUILA_LPC_REG_CONTROL1);
+    dword |= (AQUILA_LPC_CLK_PLL_RESET_MASK << AQUILA_LPC_CLK_PLL_RESET_SHIFT);
+    write_aquila_register(HOSTLPCSLAVE_BASE, AQUILA_LPC_REG_CONTROL1, dword);
+
+    // Enable LPC clock buffer
+    gpio1_out_write(gpio1_out_read() | (0x01 << 12));
+
+    // Wait a few ms for the external clock buffer to stabilize
+    k_usleep(16 * 1000);
+
+    // Bring the LPC PLL back out of reset, if present
+    // If no PLL is present, this operation does nothing
+    dword = read_aquila_register(HOSTLPCSLAVE_BASE, AQUILA_LPC_REG_CONTROL1);
+    dword &= ~(AQUILA_LPC_CLK_PLL_RESET_MASK << AQUILA_LPC_CLK_PLL_RESET_SHIFT);
+    write_aquila_register(HOSTLPCSLAVE_BASE, AQUILA_LPC_REG_CONTROL1, dword);
+
+    // Wait for LPC clock to stabilize
+    uint64_t clock_valid_timer = k_uptime_get();
+    do
+    {
+        if ((k_uptime_get() - clock_valid_timer) > 1000)
+        {
+            printf("LPC clock did not come online, aborting!\n");
+            power_off_chassis(1);
+            return -6;
+        }
+    } while (!((read_aquila_register(HOSTLPCSLAVE_BASE, AQUILA_LPC_REG_STATUS4) >> AQUILA_LPC_CLOCK_VALID_SHIFT) & AQUILA_LPC_CLOCK_VALID_MASK));
+
     host_power_status = HOST_POWER_STATUS_IPLING;
     host_power_status_changed();
     display_character('0' + 2 + host_power_status, 0); // STATUS CODE