diff --git a/src/drivers/pc80/tpm.c b/src/drivers/pc80/tpm.c
index 17e1ed7..c7b5081 100644
--- a/src/drivers/pc80/tpm.c
+++ b/src/drivers/pc80/tpm.c
@@ -127,13 +127,31 @@
 	const struct device_name* dev_names;
 };
 
+static const struct device_name atmel_devices[] = {
+	{0x3204, "AT97SC3204"},
+	{0xffff}
+};
+
 static const struct device_name infineon_devices[] = {
-	{0xb, "SLB9635 TT 1.2"},
-	{0}
+	{0x000b, "SLB9635 TT 1.2"},
+	{0xffff}
+};
+
+static const struct device_name nuvoton_devices[] = {
+	{0x00fe, "NPCT420AA V2"},
+	{0xffff}
+};
+
+static const struct device_name stmicro_devices[] = {
+	{0x0000, "ST33ZP24" },
+	{0xffff}
 };
 
 static const struct vendor_name vendor_names[] = {
+	{0x1114, "Atmel", atmel_devices},
 	{0x15d1, "Infineon", infineon_devices},
+	{0x1050, "Nuvoton", nuvoton_devices},
+	{0x104a, "ST Microelectronics", stmicro_devices},
 };
 
 /*
@@ -208,6 +226,44 @@
 }
 
 /*
+ * PC Client Specific TPM Interface Specification section 11.2.12:
+ *
+ *  Software must be prepared to send two writes of a "1" to command ready
+ *  field: the first to indicate successful read of all the data, thus
+ *  clearing the data from the ReadFIFO and freeing the TPM's resources,
+ *  and the second to indicate to the TPM it is about to send a new command.
+ *
+ * In practice not all TPMs behave the same so it is necessary to be
+ * flexible when trying to set command ready.
+ *
+ * Returns 0 on success if the TPM is ready for transactions.
+ * Returns TPM_TIMEOUT_ERR if the command ready bit does not get set.
+ */
+static int tis_command_ready(u8 locality)
+{
+	u32 status;
+
+	/* 1st attempt to set command ready */
+	tpm_write(TIS_STS_COMMAND_READY, locality, TIS_REG_STS);
+
+	/* Wait for response */
+	status = tpm_read(locality, TIS_REG_STS);
+
+	/* Check if command ready is set yet */
+	if (status & TIS_STS_COMMAND_READY)
+		return 0;
+
+	/* 2nd attempt to set command ready */
+	tpm_write(TIS_STS_COMMAND_READY, locality, TIS_REG_STS);
+
+	/* Wait for command ready to get set */
+	status = tis_wait_reg(TIS_REG_STS, locality,
+			      TIS_STS_COMMAND_READY, TIS_STS_COMMAND_READY);
+
+	return (status == TPM_TIMEOUT_ERR) ? TPM_TIMEOUT_ERR : 0;
+}
+
+/*
  * Probe the TPM device and try determining its manufacturer/device name.
  *
  * Returns 0 on success (the device is found or was found during an earlier
@@ -215,15 +271,17 @@
  */
 static u32 tis_probe(void)
 {
-	u32 didvid = tpm_read(0, TIS_REG_DID_VID);
-	int i;
 	const char *device_name = "unknown";
 	const char *vendor_name = device_name;
+	const struct device_name *dev;
+	u32 didvid;
 	u16 vid, did;
+	int i;
 
 	if (vendor_dev_id)
 		return 0;  /* Already probed. */
 
+	didvid = tpm_read(0, TIS_REG_DID_VID);
 	if (!didvid || (didvid == 0xffffffff)) {
 		printf("%s: No TPM device found\n", __FUNCTION__);
 		return TPM_DRIVER_ERR;
@@ -238,11 +296,13 @@
 		u16 known_did;
 		if (vid == vendor_names[i].vendor_id) {
 			vendor_name = vendor_names[i].vendor_name;
+		} else {
+			continue;
 		}
-		while ((known_did = vendor_names[i].dev_names[j].dev_id) != 0) {
+		dev = &vendor_names[i].dev_names[j];
+		while ((known_did = dev->dev_id) != 0xffff) {
 			if (known_did == did) {
-				device_name =
-					vendor_names[i].dev_names[j].dev_name;
+				device_name = dev->dev_name;
 				break;
 			}
 			j++;
@@ -250,7 +310,7 @@
 		break;
 	}
 	/* this will have to be converted into debug printout */
-	TPM_DEBUG("Found TPM %s by %s\n", device_name, vendor_name);
+	printf("Found TPM %s by %s\n", device_name, vendor_name);
 	return 0;
 }
 
@@ -446,7 +506,8 @@
 	}
 
 	/* Tell the TPM that we are done. */
-	tpm_write(TIS_STS_COMMAND_READY, locality, TIS_REG_STS);
+	if (tis_command_ready(locality) == TPM_TIMEOUT_ERR)
+		return TPM_DRIVER_ERR;
 
 	*len = offset;
 	return 0;
@@ -492,7 +553,11 @@
 		return TPM_DRIVER_ERR;
 	}
 
-	tpm_write(TIS_STS_COMMAND_READY, locality, TIS_REG_STS);
+	/* Certain TPMs seem to need some delay here or they hang... */
+	udelay(10);
+
+	if (tis_command_ready(locality) == TPM_TIMEOUT_ERR)
+		return TPM_DRIVER_ERR;
 
 	return 0;
 }