mb/google/guybrush: disable KBRSTEN

GPIO129 is muxed with KBRST, so setting GPIO129 to low causes reset
when KBRSTEN is set to 1. Since reset value of KBRSTEN is 1 we need a
logic to clear it.

BUG=b:183340503
TEST=build

Signed-off-by: Kangheui Won <khwon@chromium.org>
Change-Id: I194e8432a14d6105f6bcf12111647f5aad4e2de2
Reviewed-on: https://review.coreboot.org/c/coreboot/+/51727
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martinroth@google.com>
Reviewed-by: Raul Rangel <rrangel@chromium.org>

src/mainboard/google/guybrush/mainboard.c

@@ -1,9 +1,11 @@
 /* SPDX-License-Identifier: GPL-2.0-or-later */
 
+#include <amdblocks/acpimmio.h>
 #include <amdblocks/amd_pci_util.h>
 #include <baseboard/variants.h>
 #include <device/device.h>
 #include <soc/acpi.h>
+#include <soc/southbridge.h>
 #include <variant/ec.h>
 #include <vendorcode/google/chromeos/chromeos.h>
 
@@ -88,6 +90,16 @@ static void mainboard_configure_gpios(void)
 {
 	size_t base_num_gpios, override_num_gpios;
 	const struct soc_amd_gpio *base_gpios, *override_gpios;
+	u32 reg;
+
+	/*
+	 * Disable KBRST feature
+	 * KBRSTEN is set to 1 on reset and this causes system reset
+	 * if GPIO 129 is configured as GPO_LOW.
+	 * */
+	reg = pm_read8(PM_RST_CTRL1);
+	reg &= ~KBRSTEN;
+	pm_write8(PM_RST_CTRL1, reg);
 
 	base_gpios = variant_base_gpio_table(&base_num_gpios);
 	override_gpios = variant_override_gpio_table(&override_num_gpios);

src/soc/amd/cezanne/include/soc/southbridge.h

@@ -54,6 +54,7 @@
 #define   PM_ACPI_RTC_WAKE_EN		BIT(29)
 #define PM_RST_CTRL1			0xbe
 #define   SLPTYPE_CONTROL_EN		BIT(5)
+#define   KBRSTEN			BIT(4)
 #define PM_LPC_GATING			0xec
 #define   PM_LPC_AB_NO_BYPASS_EN	BIT(2)
 #define   PM_LPC_A20_EN			BIT(1)