mb/starlabs/starbook/adl: Add an option to enable Hot Plug

Some third-party SSDs, from Samsung and WD, such as the 990 Pro and
WD Black 850X aren't initialised by coreboot, seemingly as coreboot
is too quick; debug builds work, and enabling hotplug does.

Add a cmos option `pci_hot_plug`, defaulting to enabled to allow these
SSDs to work.

Signed-off-by: Sean Rhodes <sean@starlabs.systems>
Change-Id: I680211bc87153a5e6005d58040a94725c0973451
Reviewed-on: https://review.coreboot.org/c/coreboot/+/73092
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/mainboard/starlabs/starbook/cmos.default

@@ -12,6 +12,7 @@ wireless=Enable
 webcam=Enable
 microphone=Enable
 legacy_8254_timer=Disable
+pci_hot_plug=Disable
 # EC
 kbl_timeout=30 seconds
 fn_ctrl_swap=Disable

src/mainboard/starlabs/starbook/cmos.layout

@@ -28,6 +28,7 @@ entries
 512	1	e	1	webcam
 520	1	e	1	microphone
 528	1	e	1	legacy_8254_timer
+536	1	e	1	pci_hot_plug
 
 # coreboot config options: EC
 600	3	e	4	kbl_timeout

src/mainboard/starlabs/starbook/variants/adl/Makefile.inc

@@ -7,3 +7,4 @@ romstage-y += romstage.c
 ramstage-y += devtree.c
 ramstage-y += gpio.c
 ramstage-y += hda_verb.c
+ramstage-y += ramstage.c

src/mainboard/starlabs/starbook/variants/adl/ramstage.c

@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <option.h>
+#include <soc/ramstage.h>
+
+
+void mainboard_silicon_init_params(FSP_S_CONFIG *supd)
+{
+	/*
+	 * Enable Hot Plug on RP5 to slow down coreboot so that
+	 * third-party drives are detected.
+	 */
+	if (get_uint_option("pci_hot_plug", 0) == 1)
+		supd->PcieRpHotPlug[4] = 1;
+}