drivers/i2c/tpm/cr50: Simplify and increase init delay to 30 seconds

The Cr50 i2c driver provides separate entry points for probing and
initialization, but probing function does not really do much.

It also claims and releases locality on every coreboot stage, but
there is no need for this - locality should be definitely claimed
after reset and then it could be retained through the boot process.

On top of that the driver does not properly account for long time it
could take the Cr50 chip to come around to reset processing if TPM
reset request was posted during a lengthy TPM operation.

This patch addresses the issues as follows:

  - tpm_vendor_probe() and tpm_vendor_cleanup() become noops, kept
    around to conform to the expected driver API.
  - tpm_vendor_init() invokes a function to process TPM reset only in
    the first stage using TPM (typically verstage), the function
    checks if locality is claimed and if so - waits for it to be
    released, which indicates that TPM reset processing is over.
  - before claiming locality check if it is already taken, and if so -
    just proceed.

BRANCH=none
BUG=b:65867313, b:68729265
TEST=Verified that reef no longer hangs during EC reboot and
     firmware_Cr50ClearTPMOwner (not yet merged) tests.

Change-Id: Iba8445caf1342e3a5fefcb2664b0759a1a8e84e3
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://review.coreboot.org/22554
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

1 files changed, 73 insertions, 75 deletions

diff --git a/src/drivers/i2c/tpm/cr50.c b/src/drivers/i2c/tpm/cr50.c
index 9cc9e95ffb..8b0ea32269 100644
--- a/src/drivers/i2c/tpm/cr50.c
+++ b/src/drivers/i2c/tpm/cr50.c
@@ -170,57 +170,88 @@ static int cr50_i2c_write(struct tpm_chip *chip,
 	return cr50_i2c_wait_tpm_ready(chip);
 }
 
-static int check_locality(struct tpm_chip *chip, int loc)
+/*
+ * Cr50 processes reset requests asynchronously and consceivably could be busy
+ * executing a long command and not reacting to the reset pulse for a while.
+ *
+ * This function will make sure that the AP does not proceed with boot until
+ * TPM finished reset processing.
+ */
+static int process_reset(struct tpm_chip *chip)
 {
-	uint8_t mask = TPM_ACCESS_VALID | TPM_ACCESS_ACTIVE_LOCALITY;
-	uint8_t buf;
+	struct stopwatch sw;
+	uint8_t access;
+
+	/*
+	 * Locality is released by TPM reset.
+	 *
+	 * If locality is taken at this point, this could be due to the fact
+	 * that the TPM is performing a long operation and has not processed
+	 * reset request yet. We'll wait up to CR50_TIMEOUT_INIT_MS and see if
+	 * it releases locality when reset is processed.
+	 */
+	stopwatch_init_msecs_expire(&sw, CR50_TIMEOUT_INIT_MS);
+	do {
+		int rv;
+		const uint8_t mask =
+			TPM_ACCESS_VALID | TPM_ACCESS_ACTIVE_LOCALITY;
+
+		rv = cr50_i2c_read(chip, TPM_ACCESS(0),
+				   &access, sizeof(access));
+		if (rv || ((access & mask) == mask)) {
+			/*
+			 * Don't bombard the chip with traffic, let it keep
+			 * processing the command.
+			 */
+			mdelay(2);
+			continue;
+		}
 
-	if (cr50_i2c_read(chip, TPM_ACCESS(loc), &buf, 1) < 0)
-		return -1;
+		printk(BIOS_INFO, "TPM ready after %ld ms\n",
+		       stopwatch_duration_msecs(&sw));
 
-	if ((buf & mask) == mask) {
-		chip->vendor.locality = loc;
-		return loc;
-	}
+		return 0;
+	} while (!stopwatch_expired(&sw));
+
+	printk(BIOS_ERR,
+	       "TPM failed to reset after %ld ms, status: %#x\n",
+	       stopwatch_duration_msecs(&sw), access);
 
 	return -1;
 }
 
-static void release_locality(struct tpm_chip *chip, int force)
+/*
+ * Locality could be already claimed (if this is a later coreboot stage and
+ * the RO did not release it), or not yet claimed, if this is verstage or the
+ * older RO did release it.
+ */
+static int claim_locality(struct tpm_chip *chip)
 {
-	uint8_t mask = TPM_ACCESS_VALID | TPM_ACCESS_REQUEST_PENDING;
-	uint8_t addr = TPM_ACCESS(chip->vendor.locality);
-	uint8_t buf;
+	uint8_t access;
+	const uint8_t mask = TPM_ACCESS_VALID | TPM_ACCESS_ACTIVE_LOCALITY;
 
-	if (cr50_i2c_read(chip, addr, &buf, 1) < 0)
-		return;
+	if (cr50_i2c_read(chip, TPM_ACCESS(0), &access, sizeof(access)))
+		return -1;
 
-	if (force || (buf & mask) == mask) {
-		buf = TPM_ACCESS_ACTIVE_LOCALITY;
-		cr50_i2c_write(chip, addr, &buf, 1);
+	if ((access & mask) == mask) {
+		printk(BIOS_INFO, "Locality already claimed\n");
+		return 0;
 	}
 
-	chip->vendor.locality = 0;
-}
-
-static int request_locality(struct tpm_chip *chip, int loc)
-{
-	uint8_t buf = TPM_ACCESS_REQUEST_USE;
-	struct stopwatch sw;
-
-	if (check_locality(chip, loc) >= 0)
-		return loc;
+	access = TPM_ACCESS_REQUEST_USE;
+	if (cr50_i2c_write(chip, TPM_ACCESS(0),
+			   &access, sizeof(access)))
+		return -1;
 
-	if (cr50_i2c_write(chip, TPM_ACCESS(loc), &buf, 1) < 0)
+	if (cr50_i2c_read(chip, TPM_ACCESS(0), &access, sizeof(access)))
 		return -1;
 
-	stopwatch_init_msecs_expire(&sw, CR50_TIMEOUT_LONG_MS);
-	while (check_locality(chip, loc) < 0) {
-		if (stopwatch_expired(&sw))
-			return -1;
-		mdelay(CR50_TIMEOUT_SHORT_MS);
+	if ((access & mask) != mask) {
+		printk(BIOS_INFO, "Failed to claim locality.\n");
+		return -1;
 	}
-	return loc;
+
+	return 0;
 }
 
 /* cr50 requires all 4 bytes of status register to be read */
@@ -419,38 +450,6 @@ static void cr50_vendor_init(struct tpm_chip *chip)
 
 int tpm_vendor_probe(unsigned int bus, uint32_t addr)
 {
-	struct tpm_inf_dev *tpm_dev = car_get_var_ptr(&g_tpm_dev);
-	struct tpm_chip probe_chip;
-	struct stopwatch sw;
-	uint8_t buf = 0;
-	int ret;
-	long sw_run_duration = CR50_TIMEOUT_INIT_MS;
-
-	tpm_dev->bus = bus;
-	tpm_dev->addr = addr;
-
-	cr50_vendor_init(&probe_chip);
-
-	/* Wait for TPM_ACCESS register ValidSts bit to be set */
-	stopwatch_init_msecs_expire(&sw, sw_run_duration);
-	do {
-		ret = cr50_i2c_read(&probe_chip, TPM_ACCESS(0), &buf, 1);
-		if (!ret && (buf & TPM_STS_VALID)) {
-			sw_run_duration = stopwatch_duration_msecs(&sw);
-			break;
-		}
-		mdelay(CR50_TIMEOUT_SHORT_MS);
-	} while (!stopwatch_expired(&sw));
-
-	printk(BIOS_INFO,
-	       "%s: ValidSts bit %s(%d) in TPM_ACCESS register after %ld ms\n",
-	       __func__, (buf & TPM_STS_VALID) ? "set" : "clear",
-	       (buf & TPM_STS_VALID) >> 7, sw_run_duration);
-
-	/* Claim failure if the ValidSts (bit 7) is clear */
-	if (!(buf & TPM_STS_VALID))
-		return -1;
-
 	return 0;
 }
 
@@ -469,16 +468,20 @@ int tpm_vendor_init(struct tpm_chip *chip, unsigned int bus, uint32_t dev_addr)
 
 	cr50_vendor_init(chip);
 
-	if (request_locality(chip, 0) != 0)
+	if (ENV_VERSTAGE || ENV_BOOTBLOCK)
+		if (process_reset(chip))
+			return -1;
+
+	if (claim_locality(chip))
 		return -1;
 
 	/* Read four bytes from DID_VID register */
 	if (cr50_i2c_read(chip, TPM_DID_VID(0), (uint8_t *)&vendor, 4) < 0)
-		goto out_err;
+		return -1;
 
 	if (vendor != CR50_DID_VID) {
 		printk(BIOS_DEBUG, "Vendor ID 0x%08x not recognized\n", vendor);
-		goto out_err;
+		return -1;
 	}
 
 	printk(BIOS_DEBUG, "cr50 TPM 2.0 (i2c %u:0x%02x id 0x%x)\n",
@@ -486,13 +489,8 @@ int tpm_vendor_init(struct tpm_chip *chip, unsigned int bus, uint32_t dev_addr)
 
 	chip->is_open = 1;
 	return 0;
-
-out_err:
-	release_locality(chip, 1);
-	return -1;
 }
 
 void tpm_vendor_cleanup(struct tpm_chip *chip)
 {
-	release_locality(chip, 1);
 }