vc/google/chromeos: Implement platform callback for critical shutdown

This commit implements `platform_is_low_battery_shutdown_needed` and
callback for ChromeOS.

- platform_is_low_battery_shutdown_needed: API to check if low battery
   shutdown is needed.

BUG=b:339673254
TEST=Verified low battery boot event logging and controlled shutdown.

Change-Id: I119f80a45c045a6095cae98f179c755a2e948e9c
Signed-off-by: Subrata Banik <subratabanik@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/86228
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>
Reviewed-by: Julius Werner <jwerner@chromium.org>

src/vendorcode/google/chromeos/Makefile.mk

@@ -19,7 +19,10 @@ verstage-y += watchdog.c
 romstage-y += watchdog.c
 ramstage-y += watchdog.c
 
+romstage-$(CONFIG_PLATFORM_HAS_EARLY_LOW_BATTERY_INDICATOR) += battery.c
 romstage-$(CONFIG_CHROMEOS_DRAM_PART_NUMBER_IN_CBI) += dram_part_num_override.c
+
+ramstage-$(CONFIG_PLATFORM_HAS_LOW_BATTERY_INDICATOR) += battery.c
 ramstage-$(CONFIG_CHROMEOS_FW_SPLASH_SCREEN) += splash.c
 
 # Add logo to the cbfs image

src/vendorcode/google/chromeos/battery.c

@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <ec/google/chromeec/ec.h>
+#include <fsp/api.h>
+
+/*
+ * Check if low battery shutdown is needed
+ *
+ * This function checks if the system needs to shut down due to a critically low
+ * battery level. It performs the following actions:
+ *
+ * 1. If Chrome EC is not supported, returns false (no shutdown needed).
+ * 2. Uses static variables to cache the result and avoid repeated checks.
+ * 3. If the battery level has not been checked yet:
+ *    - Queries the Chrome EC to determine if the battery is below the critical threshold.
+ *    - If the battery is below the threshold, sets the result to true.
+ * 4. Returns the cached result.
+ */
+bool platform_is_low_battery_shutdown_needed(void)
+{
+	if (!CONFIG(EC_GOOGLE_CHROMEEC))
+		return false;
+
+	static bool result = false;
+	static bool checked = false;
+
+	if (!checked) {
+		if (google_chromeec_is_below_critical_threshold())
+			result = true;
+		checked = true;
+	}
+
+	return result;
+}