vc/google/chromeos: Implement splash text for low-battery/off-mode boot

This patch adds platform-level support for dynamic splash screen text
rendering on ChromeOS devices. This implementation interfaces with the
ChromeEC to retrieve battery state-of-charge and charging status,
formatting these into human-readable strings during the bootsplash
stage.

TEST=Able to build and boot google/fatcat.

Change-Id: I5dc57d60cd6be0dc9c79668a8b1560d421e4d6cc
Signed-off-by: Subrata Banik <subratabanik@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/91095
Reviewed-by: Kapil Porwal <kapilporwal@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/vendorcode/google/chromeos/Makefile.mk

@@ -24,6 +24,7 @@ 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
+ramstage-$(CONFIG_FRAMEBUFFER_SPLASH_TEXT) += splash_text.c
 ramstage-$(CONFIG_CHROMEOS_PVMFW_CBMEM) += pvmfw_cbmem.c
 
 # Add logo to the cbfs image

src/vendorcode/google/chromeos/splash_text.c

@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <bootsplash.h>
+#include <console/console.h>
+#include <ec/google/chromeec/ec.h>
+#include <stdio.h>
+#include <string.h>
+
+static bool get_battery_status_msg(char *msg, size_t msg_max)
+{
+	uint32_t batt_pct;
+
+	if (google_chromeec_read_batt_state_of_charge(&batt_pct)) {
+		printk(BIOS_WARNING, "Failed to get battery level\n");
+		return false;
+	}
+
+	if (google_chromeec_is_critically_low_on_battery()) {
+		snprintf(msg, msg_max, "%u%%", batt_pct);
+	} else if (google_chromeec_is_charger_present()) {
+		if (batt_pct == 100)
+			snprintf(msg, msg_max, "Charged");
+		else
+			snprintf(msg, msg_max, "Charging: %u%%", batt_pct);
+	}
+
+	return true;
+}
+
+bool platform_get_splash_text(enum bootsplash_type logo_type, char *msg, size_t msg_max)
+{
+	if (!CONFIG(EC_GOOGLE_CHROMEEC) || !msg || msg_max == 0)
+		return false;
+
+	memset(msg, 0, msg_max);
+
+	if (logo_type == BOOTSPLASH_LOW_BATTERY || logo_type == BOOTSPLASH_OFF_MODE_CHARGING)
+		return get_battery_status_msg(msg, msg_max);
+
+	return false;
+}