Index: head/sys/dev/tpm/tpm_tis.c
===================================================================
--- head/sys/dev/tpm/tpm_tis.c
+++ head/sys/dev/tpm/tpm_tis.c
@@ -386,12 +386,11 @@
 	mask = TPM_STS_CMD_RDY;
 	sc->intr_type = TPM_INT_STS_CMD_RDY;
 
-	OR4(sc, TPM_STS, TPM_STS_CMD_RDY);
+	WR4(sc, TPM_STS, TPM_STS_CMD_RDY);
 	bus_barrier(sc->mem_res, TPM_STS, 4, BUS_SPACE_BARRIER_WRITE);
 	if (!tpm_wait_for_u32(sc, TPM_STS, mask, mask, TPM_TIMEOUT_B))
 		return (false);
 
-	AND4(sc, TPM_STS, ~TPM_STS_CMD_RDY);
 	return (true);
 }