stm32: add hibernate support using stm32f100 standby mode

Implement the EC hibernate mode by using the stm32f100 standby low power
mode.

As we cannot de-activate the watchdog during long hibernation, the
following workaround is implemented:
we are woken-up once by the watchdog and go back to hibernate if we
detect that condition.

Signed-off-by: Vincent Palatin <vpalatin@chromium.org>

BRANCH=spring
BUG=chrome-os-partner:19595
TEST=on Spring with rework on the EC wake-up pin,
type "hibernate 10" and see the EC console going blank for 10s, then
booting with reset cause equals to "hibernate".
Press Alt+VolUp+H, then wake-up the system by pressing power key.

Change-Id: I28150e69817ae80314f52977ec6b62750017c2c4
Reviewed-on: https://gerrit.chromium.org/gerrit/58086
Tested-by: Vincent Palatin <vpalatin@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Reviewed-by: Vic Yang <victoryang@chromium.org>
Commit-Queue: Vincent Palatin <vpalatin@chromium.org>

2 files changed, 58 insertions, 14 deletions

diff --git a/chip/stm32/clock-stm32f100.c b/chip/stm32/clock-stm32f100.c
index 0dd63f456b..58c51e0a94 100644
--- a/chip/stm32/clock-stm32f100.c
+++ b/chip/stm32/clock-stm32f100.c
@@ -73,12 +73,12 @@ static void finalize_rtc_write(void)
 		;
 }
 
-uint32_t set_rtc_alarm(unsigned delay_us)
+uint32_t set_rtc_alarm(unsigned delay_s, unsigned delay_us)
 {
 	unsigned rtc_t0, rtc_t1;
 
 	rtc_t0 = ((uint32_t)STM32_RTC_CNTH << 16) | STM32_RTC_CNTL;
-	rtc_t1 = rtc_t0 + delay_us / US_PER_RTC_TICK;
+	rtc_t1 = rtc_t0 + delay_us / US_PER_RTC_TICK + delay_s * RTC_FREQ;
 
 	prepare_rtc_write();
 	/* set RTC alarm timestamp (using the 40kHz counter ) */
@@ -168,6 +168,26 @@ static void config_hispeed_clock(void)
 		;
 }
 
+void __enter_hibernate(uint32_t seconds, uint32_t microseconds)
+{
+	if (seconds || microseconds)
+		set_rtc_alarm(seconds, microseconds);
+
+	/* interrupts off now */
+	asm volatile("cpsid i");
+
+	/* enable the wake up pin */
+	STM32_PWR_CSR |= (1<<8);
+	STM32_PWR_CR |= 0xe;
+	CPU_SCB_SYSCTRL |= 0x4;
+	/* go to Standby mode */
+	asm("wfi");
+
+	/* we should never reach that point */
+	while (1)
+		;
+}
+
 #ifdef CONFIG_LOW_POWER_IDLE
 
 #ifdef CONFIG_FORCE_CONSOLE_RESUME
@@ -217,7 +237,8 @@ void __idle(void)
 			/* set deep sleep bit */
 			CPU_SCB_SYSCTRL |= 0x4;
 
-			rtc_t0 = set_rtc_alarm(next_delay - STOP_MODE_LATENCY);
+			rtc_t0 = set_rtc_alarm(0,
+					       next_delay - STOP_MODE_LATENCY);
 			asm("wfi");
 
 			CPU_SCB_SYSCTRL &= ~0x4;
diff --git a/chip/stm32/system.c b/chip/stm32/system.c
index 18e9edf044..0530624b06 100644
--- a/chip/stm32/system.c
+++ b/chip/stm32/system.c
@@ -57,6 +57,29 @@ static int bkpdata_write(enum bkpdata_index index, uint16_t value)
 	return EC_SUCCESS;
 }
 
+void __no_hibernate(uint32_t seconds, uint32_t microseconds)
+{
+	/*
+	 * Hibernate not implemented on this platform.
+	 *
+	 * Until then, treat this as a request to hard-reboot.
+	 */
+	cprintf(CC_SYSTEM, "[%T hibernate not supported, so rebooting]\n");
+	cflush();
+	system_reset(SYSTEM_RESET_HARD);
+}
+
+void __enter_hibernate(uint32_t seconds, uint32_t microseconds)
+	__attribute__((weak, alias("__no_hibernate")));
+
+void system_hibernate(uint32_t seconds, uint32_t microseconds)
+{
+	/* Flush console before hibernating */
+	cflush();
+	/* chip specific standby mode */
+	__enter_hibernate(seconds, microseconds);
+}
+
 static void check_reset_cause(void)
 {
 	uint32_t flags = bkpdata_read(BKPDATA_INDEX_SAVED_RESET_FLAGS);
@@ -98,19 +121,19 @@ static void check_reset_cause(void)
 	if (!flags && (raw_cause & 0xfe000000))
 		flags |= RESET_FLAG_OTHER;
 
-	system_set_reset_flags(flags);
-}
-
-void system_hibernate(uint32_t seconds, uint32_t microseconds)
-{
 	/*
-	 * TODO: implement hibernate.
-	 *
-	 * Until then, treat this as a request to hard-reboot.
+	 * WORKAROUND: as we cannot de-activate the watchdog during
+	 * long hibernation, we are woken-up once by the watchdog and
+	 * go back to hibernate if we detect that condition, without
+	 * watchdog initialized this time.
+	 * The RTC deadline (if any) is already set.
 	 */
-	cprintf(CC_SYSTEM, "[%T hibernate not supported, so rebooting]\n");
-	cflush();
-	system_reset(SYSTEM_RESET_HARD);
+	if ((flags & (RESET_FLAG_HIBERNATE | RESET_FLAG_WATCHDOG)) ==
+		     (RESET_FLAG_HIBERNATE | RESET_FLAG_WATCHDOG)) {
+		__enter_hibernate(0, 0);
+	}
+
+	system_set_reset_flags(flags);
 }
 
 void system_pre_init(void)