mb/google/brya: Check if descriptor is writable

Copy the `is_descriptor_writeable()` function from the `intel/adlrvp`
mainboard and use it in the `configure_pmc_descriptor()` function. With
this change, this function is now identical for both mainboards.

Change-Id: I2ff39682ed98c6b8bc60cc2218f36f4934b9903c
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/60939
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Subrata Banik <subratabanik@google.com>
Reviewed-by: Sheng Lean Tan <sheng.tan@9elements.com>

1 files changed, 30 insertions, 0 deletions

diff --git a/src/mainboard/google/brya/bootblock.c b/src/mainboard/google/brya/bootblock.c
index 1651337c49..bd7100a8dc 100644
--- a/src/mainboard/google/brya/bootblock.c
+++ b/src/mainboard/google/brya/bootblock.c
@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0-or-later */
 
+#include <arch/mmio.h>
 #include <baseboard/variants.h>
 #include <bootblock_common.h>
 #include <console/console.h>
@@ -13,6 +14,32 @@
 #define SI_DESC_REGION_SZ	4096
 #define PMC_DESC_7_BYTE3	0xc32
 
+/* Flash Master 1 : HOST/BIOS */
+#define FLMSTR1			0x80
+
+/* Flash signature Offset */
+#define FLASH_SIGN_OFFSET	0x10
+#define FLMSTR_WR_SHIFT_V2	20
+#define FLASH_VAL_SIGN		0xFF0A55A
+
+/* It checks whether host(Flash Master 1) has write access to the Descriptor Region or not */
+static int is_descriptor_writeable(uint8_t *desc)
+{
+	/* Check flash has valid signature */
+	if (read32((void *)(desc + FLASH_SIGN_OFFSET)) != FLASH_VAL_SIGN) {
+		printk(BIOS_DEBUG, "Flash Descriptor is not valid\n");
+		return 0;
+	}
+
+	/* Check host has write access to the Descriptor Region */
+	if (!((read32((void *)(desc + FLMSTR1)) >> FLMSTR_WR_SHIFT_V2) & BIT(0))) {
+		printk(BIOS_DEBUG, "Host doesn't have write access to Descriptor Region\n");
+		return 0;
+	}
+
+	return 1;
+}
+
 /* It updates PMC Descriptor in the Descriptor Region */
 static void configure_pmc_descriptor(void)
 {
@@ -29,6 +56,9 @@ static void configure_pmc_descriptor(void)
 		return;
 	}
 
+	if (!is_descriptor_writeable(si_desc_buf))
+		return;
+
 	if (si_desc_buf[PMC_DESC_7_BYTE3] != 0x40) {
 		printk(BIOS_DEBUG, "Update of PMC Descriptor is not required!\n");
 		return;