echoplayer: implement reboot using RTC_OUT pin

commit 319fdcc506791e5c5d3a2c8d080de1f6b803ff67
Author: Aidan MacDonald <[email protected]>
Date:   Thu Jan 15 00:07:50 2026 +0000

    echoplayer: implement reboot using RTC_OUT pin
    
    Change-Id: Ibeda362030c2885abe1366fb3256e925ea27538c

diff --git a/firmware/reggen/stm32h743.regs b/firmware/reggen/stm32h743.regs
index c6c25cdf4a..df8d7235ae 100644
--- a/firmware/reggen/stm32h743.regs
+++ b/firmware/reggen/stm32h743.regs
@@ -587,6 +587,10 @@ RTC @ 0x58004000 : block {
         14 00 PREDIV_S
     }
 
+    WUTR @ 0x14 : reg {
+        15 00 VALUE
+    }
+
     WPR @ 0x24 : reg {
         07 00 KEY : { 0xCA = KEY1; 0x53 = KEY2 }
     }
diff --git a/firmware/target/arm/stm32/echoplayer/power-echoplayer.c b/firmware/target/arm/stm32/echoplayer/power-echoplayer.c
index 667cd99731..63bf173d33 100644
--- a/firmware/target/arm/stm32/echoplayer/power-echoplayer.c
+++ b/firmware/target/arm/stm32/echoplayer/power-echoplayer.c
@@ -21,6 +21,8 @@
 #include "power.h"
 #include "mutex.h"
 #include "gpio-stm32h7.h"
+#include "system-echoplayer.h"
+#include "regs/cortex-m/cm_scb.h"
 
 static struct mutex power_1v8_lock;
 static int power_1v8_refcount;
@@ -68,23 +70,34 @@ void power_init(void)
 
 void power_off(void)
 {
+    /*
+     * Disable power and reset to the bootloader immediately.
+     * The system can't really be powered off as long as USB
+     * is plugged or the power button is pressed -- it's the
+     * bootloader's job to monitor those inputs and decide
+     * when the system needs to "really" power on.
+     */
     gpio_set_level(GPIO_CPU_POWER_ON, 0);
 
-    /* TODO: reset to bootloader if USB is plugged in */
-    while (1)
-        core_idle();
+    reg_writef(CM_SCB_AIRCR, VECTKEY_V(KEY), SYSRESETREQ(1));
+    while (1);
 }
 
 void system_reboot(void)
 {
     /*
-     * TODO: support reboot
-     *
-     * For R1-Rev1 PCBs doing a CPU reset will cut power when
-     * running on battery (because cpu_power_on is no longer
-     * being driven high). The RTC alarm could be used to wake
-     * the system instead.
+     * Disable IRQs to ensure an errant panic can't disturb
+     * the RTC reconfig.
+     */
+    disable_irq();
+
+    /*
+     * Configure RTC_OUT pin to keep power enabled during
+     * reset and then do a normal power off. If this fails
+     * to reset back to the bootloader then the RTC_OUT
+     * pin will go low automatically after some timeout.
      */
+    echoplayer_set_rtcout_mode(ECHOPLAYER_RTCOUT_REBOOT);
     power_off();
 }
 
diff --git a/firmware/target/arm/stm32/echoplayer/system-echoplayer.c b/firmware/target/arm/stm32/echoplayer/system-echoplayer.c
index 6a980f983e..3686ffb55b 100644
--- a/firmware/target/arm/stm32/echoplayer/system-echoplayer.c
+++ b/firmware/target/arm/stm32/echoplayer/system-echoplayer.c
@@ -22,8 +22,11 @@
 #include "button.h"
 #include "gpio-stm32h7.h"
 #include "clock-echoplayer.h"
+#include "system-echoplayer.h"
 #include "regs/stm32h743/fmc.h"
+#include "regs/stm32h743/pwr.h"
 #include "regs/stm32h743/rcc.h"
+#include "regs/stm32h743/rtc.h"
 #include "regs/cortex-m/cm_scb.h"
 
 #define F_INPUT      GPIOF_INPUT(GPIO_PULL_DISABLED)
@@ -207,9 +210,47 @@ void system_init(void)
     /* Configure GPIOs and start FMC */
     gpio_init();
     fmc_init();
+
+    /* Disable RTC_OUT pin */
+    echoplayer_set_rtcout_mode(ECHOPLAYER_RTCOUT_DISABLED);
 }
 
 void system_exception_wait(void)
 {
     while (button_read_device() != (BUTTON_POWER | BUTTON_START));
 }
+
+void echoplayer_set_rtcout_mode(enum echoplayer_rtcout_mode mode)
+{
+    reg_writef(RCC_APB4ENR, RTCAPBEN(1));
+    reg_writef(PWR_CR1, DBP(1));
+
+    reg_writef(RTC_WPR, KEY_V(KEY1));
+    reg_writef(RTC_WPR, KEY_V(KEY2));
+
+    reg_writef(RTC_OR, OUT_RMP(0), ALARM_TYPE_V(PUSH_PULL));
+
+    switch (mode)
+    {
+    case ECHOPLAYER_RTCOUT_REBOOT:
+        /*
+         * Use the inverted wakeup timer output to keep power
+         * enabled during reset. If, somehow, the system does
+         * not reset properly then the wakeup timer will drive
+         * the RTC_OUT pin low after 1 second and cut power.
+         */
+        while (!reg_readf(RTC_ISR, WUTWF));
+        reg_writef(RTC_ISR, WUTF(0));
+        reg_writef(RTC_WUTR, VALUE(STM32_LSE_FREQ / 8));
+        reg_writef(RTC_CR, OSEL_V(WAKEUP), POL(1), WUCKSEL(0), WUTE(1));
+        break;
+
+    case ECHOPLAYER_RTCOUT_DISABLED:
+    default:
+        reg_writef(RTC_CR, OSEL_V(DISABLED), POL(0), WUTE(0));
+        break;
+    }
+
+    reg_writef(RTC_WPR, KEY(0));
+    reg_writef(PWR_CR1, DBP(0));
+}
diff --git a/firmware/target/arm/stm32/echoplayer/system-echoplayer.h b/firmware/target/arm/stm32/echoplayer/system-echoplayer.h
new file mode 100644
index 0000000000..3f93d84e30
--- /dev/null
+++ b/firmware/target/arm/stm32/echoplayer/system-echoplayer.h
@@ -0,0 +1,32 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2026 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.
+ *
+ ****************************************************************************/
+#ifndef __SYSTEM_ECHOPLAYER_H__
+#define __SYSTEM_ECHOPLAYER_H__
+
+enum echoplayer_rtcout_mode
+{
+    ECHOPLAYER_RTCOUT_DISABLED,
+    ECHOPLAYER_RTCOUT_REBOOT,
+};
+
+void echoplayer_set_rtcout_mode(enum echoplayer_rtcout_mode mode);
+
+#endif /* __SYSTEM_ECHOPLAYER_H__ */
-- 
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