fwk: dogwood: Repurpose "APU_EC_INT" to be a 4th RAM ID bit

We're running out of RAM ID pins going to the AP. This is a problem because
we need a little more RAM options than expected (eg: multi-sourcing).

Since we can't really change the board anymore to add more bits,
we need another method.

Luckly the APU_EC_INT signal going between the EC->AP is unused
(despite its name). It was originally added for some HID interrupts.
We never needed that.
This signal is also not to be confused with the normal EC->AP interrupt
method that happens inband over eSPI,

The proposal is for the AP to use this APU_EC_INT as a 4th RAM ID bit.

How will the EC know when to assert this? We'll use the EC board ID
(toggling between 9 and 10) to disambiguate between the 2 states
for this 4th RAM_ID bit.
NOTE: otherwise board_id 9 and 10 are exactly the same as far as
the EC is concerned.

BRANCH=fwk-dogwood-27111
BUG=https://app.clickup.com/t/86euhhg7k
See https://docs.google.com/presentation/d/1n1WNI4WoaVsPbWK_gPJw2rZpELAfXCdn for more details.
TEST=on dogwood, when board version id = 10, APU_EC_INT will keep low.

Author: LeoCX-Tsai

zephyr/program/framework/dogwood/gpio.dtsi

@@ -6,6 +6,7 @@
 / {
 	aliases {
 		gpio-diagnostic-led4 = &gpio_led4_drv;
+		gpio-mem-id3 = &gpio_mem_id3;
 	};
 
 	named-gpios {
@@ -54,10 +55,15 @@
 			gpios = <&gpio2 7 GPIO_ODR_LOW>;
 		};
 		gpio_apu_ec_int2_l: apu_ec_int2_l {
-			gpios = <&gpio1 5 GPIO_ODR_HIGH>;	/* reserved for HID interrupt */
-		};
-		gpio_apu_ec_int_l: apu_ec_int_l {
-			gpios = <&gpio1 4 GPIO_ODR_HIGH>;	/* reserved for HID interrupt */
+			/* originally reserved for HID interrupt */
+			/* unused currently */
+			gpios = <&gpio1 5 GPIO_ODR_HIGH>;
+		};
+		gpio_mem_id3: mem_id3 {
+			/* On the schematic: APU_EC_INT#_Q */
+			/* originally reserved for HID interrupt, never used for that */
+			/* now used as a 4th RAM_ID bit */
+			gpios = <&gpio1 4 GPIO_ODR_HIGH>;
 		};
 		gpio_argb_dir: argb_dir {
 			gpios = <&gpio3 5 GPIO_OUTPUT_HIGH>;	/* ARGB_DIR */

zephyr/program/framework/dogwood/src/power_sequence.c

@@ -991,6 +991,20 @@ static void power_select_power_signal(void)
 }
 DECLARE_HOOK(HOOK_INIT, power_select_power_signal, HOOK_PRIO_INIT_CHIPSET - 1);
 
+static void apu_ram_select(void)
+{
+	/* We needed an extra MEM_ID toward the APU. Since we can't
+	 * change the schematic, the only other way to do this is
+	 * for the EC to act like a proxy. */
+
+	/* The EC will know the state of MEM_ID3 depending
+	 * on the board version that the EC sees (9 vs 10) */
+
+	if (board_get_version() >= BOARD_VERSION_10)
+		gpio_pin_configure_dt(GPIO_DT_FROM_ALIAS(gpio_mem_id3), GPIO_ODR_LOW);
+}
+DECLARE_HOOK(HOOK_INIT, apu_ram_select, HOOK_PRIO_INIT_ADC + 1);
+
 __override int chipset_in_low_power_mode(void)
 {
 	volatile uint32_t *address;