ec/google/chromeec: Add SoC calculation from battery dynamic info

Implement google_chromeec_read_batt_state_of_charge_raw() to
calculate the battery percentage using raw capacity metrics.

Unlike the standard charge state command, this function retrieves data
via EC_CMD_BATTERY_GET_DYNAMIC. It manually calculates the State of
Charge (SoC) by comparing remaining_capacity against full_capacity.

This provides a fallback mechanism for platforms where the high-level
CHARGE_STATE_CMD_GET_STATE command is not implemented or when working
directly with the fuel gauge's dynamic data cache.

Includes:
- Zero-capacity check to prevent division by zero.
- 100% clamping to handle fuel gauge rounding/calibration drift.

Change-Id: I86d6313884762140884762140884762140884762
Signed-off-by: Subrata Banik <subratabanik@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/90615
Reviewed-by: Kapil Porwal <kapilporwal@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/ec/google/chromeec/ec.c

@@ -1884,3 +1884,37 @@ int google_chromeec_read_batt_state_of_charge(uint32_t *state)
 	*state = resp.get_state.batt_state_of_charge;
 	return 0;
 }
+
+/*
+ * Calculates SoC from dynamic battery data.
+ *
+ * This function fetches "dynamic" battery metrics (voltage, current, and capacity)
+ * and manually calculates the percentage. This is often used when the high-level
+ * "Get Charge State" command is unavailable.
+ *
+ * Return: 0 on success, -1 on communication failure or invalid battery data.
+ * Return Value (state): Pointer to store the calculated State of Charge (0-100%).
+ */
+int google_chromeec_read_batt_state_of_charge_raw(uint32_t *state)
+{
+	struct ec_params_battery_dynamic_info params = {
+		.index = 0,
+	};
+	struct ec_response_battery_dynamic_info resp;
+
+	if (ec_cmd_battery_get_dynamic(PLAT_EC, &params, &resp) != 0)
+		return -1;
+
+	if (resp.full_capacity <= 0)
+		return -1;
+
+	uint32_t soc = (uint32_t)resp.remaining_capacity * 100 / (uint32_t)resp.full_capacity;
+
+	/* Clamp the value to 100% (some fuel gauges report slight overflows) */
+	if (soc > 100)
+		soc = 100;
+
+	*state = soc;
+
+	return 0;
+}

src/ec/google/chromeec/ec.h

@@ -546,4 +546,13 @@ void chipset_ioport_range(uint16_t *base, size_t *size);
  */
 int google_chromeec_read_batt_state_of_charge(uint32_t *state);
 
+/*
+ * Reads the current battery charge percentage from EC dynamic info CMD.
+ * This is often used when the high-level "Get Charge State" command is unavailable".
+ *
+ * @param state		Pointer to a uint32_t where the battery state of charge (0-100) will be
+ *			stored.
+ */
+int google_chromeec_read_batt_state_of_charge_raw(uint32_t *state);
+
 #endif /* _EC_GOOGLE_CHROMEEC_EC_H */