[PATCH] tpm_tis: TPM_STS_DATA_EXPECT workaround

[Rajiv Andrade <srajiv@linux.vnet.ibm.com>]

Some newer Lenovo models are shipped with a TPM that doesn't seem to set the TPM_STS_DATA_EXPECT status bit
when sending it a burst of data, so the code understands it as a failure and doesn't proceed sending the chip
the intended data. In this patch we bypass this bit check in case the itpm module parameter was set.

This patch is based on Andy Isaacson's one:

http://marc.info/?l=linux-kernel&m=124650185023495&w=2

It was heavily discussed how should we deal with identifying the chip in kernel space, but the required
patch to do so was NACK'd:

http://marc.info/?l=linux-kernel&m=124650186423711&w=2

This way we let the user choose using this workaround or not based on his
observations on this code behavior when trying to use the TPM.

Signed-off-by: Rajiv Andrade <srajiv@linux.vnet.ibm.com>
---
diff --git a/drivers/char/tpm/tpm_tis.c b/drivers/char/tpm/tpm_tis.c
index aec1931..c9990db 100644
--- a/drivers/char/tpm/tpm_tis.c
+++ b/drivers/char/tpm/tpm_tis.c
@@ -257,6 +257,10 @@ out:
 	return size;
 }
 
+static int itpm = 0;
+module_param(itpm, bool, 0444);
+MODULE_PARM_DESC(itpm, "Force iTPM workarounds (found on some Lenovo laptops)");
+
 /*
  * If interrupts are used (signaled by an irq set in the vendor structure)
  * tpm.c can skip polling for the data to be available as the interrupt is
@@ -293,7 +297,7 @@ static int tpm_tis_send(struct tpm_chip *chip, u8 *buf, size_t len)
 		wait_for_stat(chip, TPM_STS_VALID, chip->vendor.timeout_c,
 			      &chip->vendor.int_queue);
 		status = tpm_tis_status(chip);
-		if ((status & TPM_STS_DATA_EXPECT) == 0) {
+		if (!itpm && (status & TPM_STS_DATA_EXPECT) == 0) {
 			rc = -EIO;
 			goto out_err;
 		}
@@ -467,6 +471,10 @@ static int tpm_tis_init(struct device *dev, resource_size_t start,
 		 "1.2 TPM (device-id 0x%X, rev-id %d)\n",
 		 vendor >> 16, ioread8(chip->vendor.iobase + TPM_RID(0)));
 
+	if (itpm) 
+		dev_info(dev, "Intel iTPM workaround enabled\n");
+
+
 	/* Figure out the capabilities */
 	intfcaps =
 	    ioread32(chip->vendor.iobase +