PATCH: Google security chip, additional DID:VID

* PATCH: Google security chip, additional DID:VID
@ 2022-04-04 23:00 Jes Klinke
  2022-04-04 23:21 ` Eric Biggers
  0 siblings, 1 reply; 4+ messages in thread
From: Jes Klinke @ 2022-04-04 23:00 UTC (permalink / raw)
  To: Peter Huewe; +Cc: linux-integrity

Hello Peter,

I am a firmware engineer working on the TPM chip in Chromebooks (known
as cr50).  As we plan to deploy a new codebase on our TPM chips, we
will have them present a new DID:VID value, but otherwise follow the
same protocol as the existing implementations.

The below patch has the effect of accepting one additional numerical
value, and logging one of two messages, depending on the value.
Unfortunately, I had to reverse the indentation, so the diff appears
to touch more lines than it needed to do.

I am unsure which procedure to follow, as this is my first kernel
patch.  Let me know if posting the patch inline like this is not the
way to go.

Regards
Jes Bodi Klinke

diff --git a/drivers/char/tpm/tpm_tis_i2c_cr50.c
b/drivers/char/tpm/tpm_tis_i2c_cr50.c
index f6c0affbb4567..e5fb1ecc8fa2e 100644
--- a/drivers/char/tpm/tpm_tis_i2c_cr50.c
+++ b/drivers/char/tpm/tpm_tis_i2c_cr50.c
@@ -31,6 +31,7 @@
 #define TPM_CR50_TIMEOUT_SHORT_MS 2 /* Short timeout during transactions */
 #define TPM_CR50_TIMEOUT_NOIRQ_MS 20 /* Timeout for TPM ready without IRQ */
 #define TPM_CR50_I2C_DID_VID 0x00281ae0L /* Device and vendor ID reg value */
+#define TPM_TI50_I2C_DID_VID 0x504a6666L /* Device and vendor ID reg value */
 #define TPM_CR50_I2C_MAX_RETRIES 3 /* Max retries due to I2C errors */
 #define TPM_CR50_I2C_RETRY_DELAY_LO 55 /* Min usecs between retries on I2C */
 #define TPM_CR50_I2C_RETRY_DELAY_HI 65 /* Max usecs between retries on I2C */
@@ -742,16 +743,20 @@ static int tpm_cr50_i2c_probe(struct i2c_client *client)
  }

  vendor = le32_to_cpup((__le32 *)buf);
- if (vendor != TPM_CR50_I2C_DID_VID) {
- dev_err(dev, "Vendor ID did not match! ID was %08x\n", vendor);
- tpm_cr50_release_locality(chip, true);
- return -ENODEV;
+ if (vendor == TPM_CR50_I2C_DID_VID) {
+ dev_info(dev, "cr50 TPM 2.0 (i2c 0x%02x irq %d id 0x%x)\n",
+ client->addr, client->irq, vendor >> 16);
+ return tpm_chip_register(chip);
+ }
+ if (vendor == TPM_TI50_I2C_DID_VID) {
+ dev_info(dev, "ti50 TPM 2.0 (i2c 0x%02x irq %d id 0x%x)\n",
+ client->addr, client->irq, vendor >> 16);
+ return tpm_chip_register(chip);
  }

- dev_info(dev, "cr50 TPM 2.0 (i2c 0x%02x irq %d id 0x%x)\n",
- client->addr, client->irq, vendor >> 16);
-
- return tpm_chip_register(chip);
+ dev_err(dev, "Vendor ID did not match! ID was %08x\n", vendor);
+ tpm_cr50_release_locality(chip, true);
+ return -ENODEV;
 }

 /**

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