mb/google/bluey: Implement slow-to-fast charging transition logic

Update the charging flow to support a transition from slow charging
to fast charging based on the battery threshold.

Key changes:
- Pass boot_mode to launch_charger_applet() to allow mode-specific
  power management.
- In LB_BOOT_MODE_LOW_BATTERY_CHARGING, if the battery is above the
  critical threshold, issue an AP power-off to trigger a transition
  from slow to fast charging mode.
- Update handle_low_power_charging_boot() to default to slow charging
  for low-battery charging boots.

BUG=b:497622018
TEST=Verified Bluey correctly switches from slow charging to fast
charging once critical battery threshold is exceeded.

Change-Id: Ic65ab99360496c92a91795fce1352159066ab94e
Signed-off-by: Subrata Banik <subratabanik@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/91912
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kapil Porwal <kapilporwal@google.com>

src/mainboard/google/bluey/board.h

@@ -4,6 +4,7 @@
 #define MAINBOARD_GOOGLE_BLUEY_BOARD_H
 
 #include <assert.h>
+#include <commonlib/coreboot_tables.h>
 #include <gpio.h>
 
 #define GPIO_AP_EC_INT		GPIO(67)
@@ -66,6 +67,7 @@ void configure_dam_on_system_state_change(bool poweron);
 void enable_slow_battery_charging(void);
 void disable_slow_battery_charging(void);
 void launch_charger_applet(void);
+bool platform_get_battery_soc_information(uint32_t *batt_pct);
 void enable_fast_battery_charging(void);
 
 #endif /* MAINBOARD_GOOGLE_BLUEY_BOARD_H */

src/mainboard/google/bluey/charging.c

@@ -61,6 +61,7 @@
 
 #define DELAY_CHARGING_APPLET_MS 2000 /* 2sec */
 #define CHARGING_RAIL_STABILIZATION_DELAY_MS 3000 /* 3sec */
+#define LOW_BATTERY_CHARGING_LOOP_EXIT_MS (10 * 60 * 1000) /* 10min */
 #define DELAY_CHARGING_ACTIVE_LB_MS 4000 /* 4sec */
 
 enum charging_status {
@@ -162,6 +163,7 @@ void launch_charger_applet(void)
 	static const long charging_enable_timeout_ms = CHARGING_RAIL_STABILIZATION_DELAY_MS;
 	struct stopwatch sw;
 	bool has_crossed_threshold = false;
+	bool has_entered_low_battery_mode = false;
 
 	printk(BIOS_INFO, "Inside %s. Initiating charging\n", __func__);
 
@@ -191,10 +193,37 @@ void launch_charger_applet(void)
 	}
 	printk(BIOS_INFO, "Charging ready after %lld ms\n", stopwatch_duration_msecs(&sw));
 
+	static const long low_battery_charging_timeout_ms = LOW_BATTERY_CHARGING_LOOP_EXIT_MS;
+	uint32_t batt_pct;
+	if (!platform_get_battery_soc_information(&batt_pct)) {
+		printk(BIOS_WARNING, "Failed to get battery level\n");
+		return;
+	}
+	/*
+	 * If the battery is at 0%, enter low-battery charging mode and
+	 * start a timeout timer to prevent getting stuck in a dead-loop
+	 * if the battery fails to charge.
+	 *
+	 * FIXME: b/497622018
+	 */
+	if (!batt_pct) {
+		has_entered_low_battery_mode = true;
+		stopwatch_init_msecs_expire(&sw, low_battery_charging_timeout_ms);
+	}
+
 	do {
 		/* Add static delay before reading the charging applet pre-requisites */
 		mdelay(DELAY_CHARGING_APPLET_MS);
 
+		if (has_entered_low_battery_mode) {
+			if (stopwatch_expired(&sw)) {
+				printk(BIOS_INFO, "Issuing power-off as switching from slow charging "
+						"to fast charging mode.\n");
+				configure_dam_on_system_state_change(false);
+				google_chromeec_ap_poweroff();
+			}
+		}
+
 		/*
 		 * Issue a shutdown if not charging.
 		 */
@@ -328,3 +357,14 @@ void enable_fast_battery_charging(void)
 		printk(BIOS_ERR, "LPASS bring-up failed; skipping fast charging.\n");
 	}
 }
+
+bool platform_get_battery_soc_information(uint32_t *batt_pct)
+{
+	if (!CONFIG(EC_GOOGLE_CHROMEEC))
+		return false;
+
+	if (google_chromeec_read_batt_state_of_charge(batt_pct))
+		return false;
+
+	return true;
+}

src/mainboard/google/bluey/mainboard.c

@@ -192,7 +192,22 @@ static void handle_low_power_charging_boot(void)
 	if (!pll_init_and_set(apss_ncc0, L_VAL_710P4MHz))
 		printk(BIOS_DEBUG, "CPU Frequency set to 710MHz\n");
 
-	enable_fast_battery_charging();
+	uint32_t batt_pct;
+	if (!platform_get_battery_soc_information(&batt_pct)) {
+		printk(BIOS_WARNING, "Failed to get battery level\n");
+		return;
+	}
+
+	/*
+	 * Use slow charging for a completely depleted battery (0% SoC)
+	 * to ensure stability; otherwise, enable fast charging.
+	 *
+	 * FIXME: b/497622018
+	 */
+	if (!batt_pct)
+		enable_slow_battery_charging();
+	else
+		enable_fast_battery_charging();
 
 	/*
 	 * Disable the lightbar for Low-Battery or Off-Mode charging sequences.

src/mainboard/google/bluey/romstage.c

@@ -105,15 +105,6 @@ int qclib_mainboard_override(struct qclib_cb_if_table *table)
 	return 0;
 }
 
-static void platform_dump_battery_soc_information(void)
-{
-	uint32_t batt_pct;
-	if (google_chromeec_read_batt_state_of_charge(&batt_pct))
-		printk(BIOS_WARNING, "Failed to get battery level\n");
-	else
-		printk(BIOS_INFO, "Battery state-of-charge %d%%\n", batt_pct);
-}
-
 static void early_setup_usb_typec(void)
 {
 	gpio_output(GPIO_USB_C1_RETIMER_RESET_L, 0);
@@ -158,8 +149,13 @@ void platform_romstage_main(void)
 	/* Watchdog must be checked first to avoid erasing watchdog info later. */
 	check_wdog();
 
-	if (CONFIG(EC_GOOGLE_CHROMEEC) && CONFIG(CONSOLE_SERIAL))
-		platform_dump_battery_soc_information();
+	if (CONFIG(EC_GOOGLE_CHROMEEC) && CONFIG(CONSOLE_SERIAL)) {
+		uint32_t batt_pct;
+		if (platform_get_battery_soc_information(&batt_pct))
+			printk(BIOS_INFO, "Battery state-of-charge %d%%\n", batt_pct);
+		else
+			printk(BIOS_WARNING, "Failed to get battery level\n");
+	}
 
 	if (!qclib_check_dload_mode())
 		shrm_fw_load_reset();