mb/google/brya/brya0: Manually probe fw_config for DB_LTE

In order to use the USB WWAN module in USB mode (as opposed to PCIe),
the PCIe RP must be turned off at the FSP level. The `probe` statement
in the devicetree unfortunately takes effect too late, because the UPDs
for disabling/enabling PCIE RP belong to FSP-M (romstage), whereas
fw_config probing for devicetree is done in ramstage.

Add a new variant-specific file which will handle manually setting the
UPD based on FW_CONFIG instead.

BUG=b:180166408
TEST=set CBI FW_CONFIG field to LTE_USB, see message in console,
set field to LTE_PCIE, do not see message in console.

Change-Id: Ica2f64ec99fa547e233012dc201577a14f6aa7d7
Signed-off-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/54633
Reviewed-by: EricR Lai <ericr_lai@compal.corp-partner.google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/google/brya/romstage.c

@@ -17,4 +17,6 @@ void mainboard_memory_init_params(FSPM_UPD *memupd)
 	};
 
 	memcfg_init(&memupd->FspmConfig, mem_config, &spd_info, half_populated);
+
+	variant_update_fspm_upds(memupd);
 }

src/mainboard/google/brya/variants/baseboard/include/baseboard/variants.h

@@ -3,6 +3,7 @@
 #ifndef __BASEBOARD_VARIANTS_H__
 #define __BASEBOARD_VARIANTS_H__
 
+#include <fsp/api.h>
 #include <soc/gpio.h>
 #include <soc/meminit.h>
 #include <stdint.h>
@@ -19,4 +20,6 @@ const struct mb_cfg *variant_memory_params(void);
 int variant_memory_sku(void);
 bool variant_is_half_populated(void);
 
+void variant_update_fspm_upds(FSPM_UPD *memupd);
+
 #endif /*__BASEBOARD_VARIANTS_H__ */

src/mainboard/google/brya/variants/brya0/Makefile.inc

@@ -0,0 +1,2 @@
+romstage-y += variant.c
+ramstage-y += variant.c

src/mainboard/google/brya/variants/brya0/overridetree.cb

@@ -122,9 +122,6 @@ chip soc/intel/alderlake
 				device generic 0 on end
 			end
 		end
-		device ref pcie_rp6 on
-			probe DB_LTE LTE_PCIE
-		end
 		device ref pcie_rp8 on
 			chip soc/intel/common/block/pcie/rtd3
 				register "enable_gpio" = "ACPI_GPIO_OUTPUT_ACTIVE_HIGH(GPP_H13)"

src/mainboard/google/brya/variants/brya0/variant.c

@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <baseboard/variants.h>
+#include <console/console.h>
+#include <fw_config.h>
+
+void variant_update_fspm_upds(FSPM_UPD *memupd)
+{
+	if (fw_config_probe(FW_CONFIG(DB_LTE, LTE_USB))) {
+		FSP_M_CONFIG *m_cfg = &memupd->FspmConfig;
+		printk(BIOS_INFO, "Disabling PCIe RP 6 UPD for USB WWAN\n");
+		m_cfg->PcieRpEnableMask &= ~BIT(5);
+	}
+}