1 files changed, 28 insertions, 0 deletions
diff --git a/src/soc/amd/common/block/cpu/smm/smm_helper.c b/src/soc/amd/common/block/cpu/smm/smm_helper.c
new file mode 100644
index 0000000000..bf01b8b965
--- /dev/null
+++ b/src/soc/amd/common/block/cpu/smm/smm_helper.c
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <amdblocks/smm.h>
+#include <console/console.h>
+#include <cpu/x86/msr.h>
+#include <cpu/amd/msr.h>
+
+/*
+ * For data stored in TSEG, ensure TValid is clear so R/W access can reach
+ * the DRAM when not in SMM.
+ */
+void clear_tvalid(void)
+{
+	msr_t hwcr = rdmsr(HWCR_MSR);
+	msr_t mask = rdmsr(SMM_MASK_MSR);
+	int tvalid = !!(mask.lo & SMM_TSEG_VALID);
+
+	if (hwcr.lo & SMM_LOCK) {
+		if (!tvalid) /* not valid but locked means still accessible */
+			return;
+
+		printk(BIOS_ERR, "Error: can't clear TValid, already locked\n");
+		return;
+	}
+
+	mask.lo &= ~SMM_TSEG_VALID;
+	wrmsr(SMM_MASK_MSR, mask);
+}