drivers/spi/tpm: Enable long cr50 ready pulses for Tiger Lake systems

For Volteer (and future Tiger Lake boards) we can enable mode S0i3.4
only if we know that the Cr50 is generating 100us interrupt pulses.
We have to do so, because the SoC is not guaranteed to detect pulses
shorter than 100us in S0i3.4 substate.

A new Kconfig setting CR50_USE_LONG_INTERRUPT_PULSES controls new code
running in verstage, which will program a new Cr50 register, provided that
Cr50 firmware is new enough to support the register.

BUG=b:154333137
TEST=util/abuild/abuild -t GOOGLE_VOLTEER -c max -x

Signed-off-by: Jes Bodi Klinke <jbk@chromium.org>
Change-Id: If83188fd09fe69c2cda4ce1a8bf5b2efe1ca86da
Reviewed-on: https://review.coreboot.org/c/coreboot/+/43741
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Julius Werner <jwerner@chromium.org>

3 files changed, 147 insertions, 25 deletions

diff --git a/src/drivers/spi/tpm/tpm.c b/src/drivers/spi/tpm/tpm.c
index 4263dce523..bc40e852a2 100644
--- a/src/drivers/spi/tpm/tpm.c
+++ b/src/drivers/spi/tpm/tpm.c
@@ -31,6 +31,15 @@
 #define TPM_DID_VID_REG   (TPM_LOCALITY_0_SPI_BASE + 0xf00)
 #define TPM_RID_REG       (TPM_LOCALITY_0_SPI_BASE + 0xf04)
 #define TPM_FW_VER	  (TPM_LOCALITY_0_SPI_BASE + 0xf90)
+#define CR50_BOARD_CFG     (TPM_LOCALITY_0_SPI_BASE + 0xfe0)
+
+#define CR50_BOARD_CFG_LOCKBIT_MASK 0x80000000U
+#define CR50_BOARD_CFG_FEATUREBITS_MASK 0x3FFFFFFFU
+
+#define CR50_BOARD_CFG_100US_READY_PULSE 0x00000001U
+#define CR50_BOARD_CFG_VALUE \
+		(CONFIG(CR50_USE_LONG_INTERRUPT_PULSES) \
+		 ? CR50_BOARD_CFG_100US_READY_PULSE : 0)
 
 #define CR50_TIMEOUT_INIT_MS 30000 /* Very long timeout for TPM init */
 
@@ -39,6 +48,12 @@ static struct spi_slave spi_slave;
 
 /* Cached TPM device identification. */
 static struct tpm2_info tpm_info;
+struct cr50_firmware_version {
+	int epoch;
+	int major;
+	int minor;
+};
+static struct cr50_firmware_version cr50_firmware_version;
 
 /*
  * TODO(vbendeb): make CONFIG(DEBUG_TPM) an int to allow different level of
@@ -421,12 +436,109 @@ static int tpm2_claim_locality(void)
 	return 0;
 }
 
+static int cr50_parse_fw_version(const char *version_str, struct cr50_firmware_version *ver)
+{
+	int epoch, major, minor;
+
+	char *number = strstr(version_str, " RW_A:");
+	if (!number)
+		number = strstr(version_str, " RW_B:");
+	if (!number)
+		return -1;
+	number += 6; /* Skip past the colon. */
+
+	epoch = skip_atoi(&number);
+	if (*number++ != '.')
+		return -2;
+	major = skip_atoi(&number);
+	if (*number++ != '.')
+		return -2;
+	minor = skip_atoi(&number);
+
+	ver->epoch = epoch;
+	ver->major = major;
+	ver->minor = minor;
+	return 0;
+}
+
+static int cr50_fw_supports_board_cfg(struct cr50_firmware_version *version)
+{
+	/* Cr50 supports the CR50_BOARD_CFG register from version 0.5.5 / 0.6.5
+	 * and onwards. */
+	if (version->epoch > 0 || version->major >= 7
+	    || (version->major >= 5 && version->minor >= 5))
+		return 1;
+	printk(BIOS_INFO, "Cr50 firmware does not support CR50_BOARD_CFG, version: %d.%d.%d\n",
+	       version->epoch, version->major, version->minor);
+	return 0;
+}
+
+/**
+ * Set the BOARD_CFG register on the TPM chip to a particular compile-time constant value.
+ */
+static void cr50_set_board_cfg(void)
+{
+	uint32_t board_cfg_value;
+	if (!cr50_fw_supports_board_cfg(&cr50_firmware_version))
+		return;
+	/* Set the CR50_BOARD_CFG register, for e.g. asking cr50 to use longer ready pulses. */
+	if (!tpm2_read_reg(CR50_BOARD_CFG, &board_cfg_value, sizeof(board_cfg_value))) {
+		printk(BIOS_INFO, "Error reading from cr50\n");
+		return;
+	}
+	if ((board_cfg_value & CR50_BOARD_CFG_FEATUREBITS_MASK) == CR50_BOARD_CFG_VALUE) {
+		printk(BIOS_INFO,
+		       "Current CR50_BOARD_CFG = 0x%08x, matches desired = 0x%08x\n",
+		       board_cfg_value, CR50_BOARD_CFG_VALUE);
+		return;
+	}
+	if (board_cfg_value & CR50_BOARD_CFG_LOCKBIT_MASK) {
+		/* The high bit is set, meaning that the Cr50 is already locked on a particular
+		 * value for the register, but not the one we wanted. */
+		printk(BIOS_ERR,
+		       "ERROR: Current CR50_BOARD_CFG = 0x%08x, does not match desired = 0x%08x\n",
+		       board_cfg_value, CR50_BOARD_CFG_VALUE);
+		return;
+	}
+	printk(BIOS_INFO, "Current CR50_BOARD_CFG = 0x%08x, setting to 0x%08x\n",
+	       board_cfg_value, CR50_BOARD_CFG_VALUE);
+	board_cfg_value = CR50_BOARD_CFG_VALUE;
+	if (!tpm2_write_reg(CR50_BOARD_CFG, &board_cfg_value, sizeof(board_cfg_value)))
+		printk(BIOS_INFO, "Error writing to cr50\n");
+}
+
+/*
+ * Expose method to read the CR50_BOARD_CFG register, will return zero if
+ * register not supported by Cr50 firmware.
+ */
+static uint32_t cr50_get_board_cfg(void)
+{
+	uint32_t board_cfg_value;
+	if (!cr50_fw_supports_board_cfg(&cr50_firmware_version))
+		return 0;
+	if (!tpm2_read_reg(CR50_BOARD_CFG, &board_cfg_value, sizeof(board_cfg_value))) {
+		printk(BIOS_INFO, "Error reading from cr50\n");
+		return 0;
+	}
+	return board_cfg_value & CR50_BOARD_CFG_FEATUREBITS_MASK;
+}
+
+bool cr50_is_long_interrupt_pulse_enabled(void)
+{
+	return cr50_get_board_cfg() & CR50_BOARD_CFG_100US_READY_PULSE;
+}
+
 /* Device/vendor ID values of the TPM devices this driver supports. */
 static const uint32_t supported_did_vids[] = {
 	0x00281ae0,  /* H1 based Cr50 security chip. */
 	0x0000104a   /* ST33HTPH2E32 */
 };
 
+static int first_access_this_boot(void)
+{
+	return ENV_SEPARATE_VERSTAGE || ENV_BOOTBLOCK || !CONFIG(VBOOT);
+}
+
 int tpm2_init(struct spi_slave *spi_if)
 {
 	uint32_t did_vid, status;
@@ -471,7 +583,7 @@ int tpm2_init(struct spi_slave *spi_if)
 	printk(BIOS_INFO, " done!\n");
 
 	// FIXME: Move this to tpm_setup()
-	if (ENV_SEPARATE_VERSTAGE || ENV_BOOTBLOCK || !CONFIG(VBOOT))
+	if (first_access_this_boot())
 		/*
 		 * Claim locality 0, do it only during the first
 		 * initialization after reset.
@@ -502,18 +614,10 @@ int tpm2_init(struct spi_slave *spi_if)
 	       tpm_info.vendor_id, tpm_info.device_id, tpm_info.revision);
 
 	/* Let's report device FW version if available. */
-	if (tpm_info.vendor_id == 0x1ae0) {
+	if (CONFIG(TPM_CR50) && tpm_info.vendor_id == 0x1ae0) {
 		int chunk_count = 0;
-		size_t chunk_size;
-		/*
-		 * let's read 50 bytes at a time; leave room for the trailing
-		 * zero.
-		 */
-		char vstr[51];
-
-		chunk_size = sizeof(vstr) - 1;
-
-		printk(BIOS_INFO, "Firmware version: ");
+		size_t chunk_size = 50;
+		char version_str[301];
 
 		/*
 		 * Does not really matter what's written, this just makes sure
@@ -521,20 +625,28 @@ int tpm2_init(struct spi_slave *spi_if)
 		 */
 		tpm2_write_reg(TPM_FW_VER, &chunk_size, 1);
 
-		/* Print it out in sizeof(vstr) - 1 byte chunks. */
-		vstr[chunk_size] = 0;
+		/*
+		 * Read chunk_size bytes at a time, last chunk will be zero padded.
+		 */
 		do {
-			tpm2_read_reg(TPM_FW_VER, vstr, chunk_size);
-			printk(BIOS_INFO, "%s", vstr);
-
-			/*
-			 * While string is not over, and is no longer than 300
-			 * characters.
-			 */
-		} while (vstr[chunk_size - 1] &&
-			 (chunk_count++ < (300 / chunk_size)));
-
-		printk(BIOS_INFO, "\n");
+			tpm2_read_reg(TPM_FW_VER,
+				      version_str + chunk_count * chunk_size,
+				      chunk_size);
+			if (!version_str[++chunk_count * chunk_size - 1])
+				/* Zero padding detected: end of string. */
+				break;
+			/* Check if there is enough room for reading one more chunk. */
+		} while (chunk_count * chunk_size < sizeof(version_str) - chunk_size);
+		version_str[chunk_count * chunk_size] = '\0';
+		printk(BIOS_INFO, "Firmware version: %s\n", version_str);
+		if (cr50_parse_fw_version(version_str, &cr50_firmware_version)) {
+			printk(BIOS_ERR, "Did not recognize Cr50 version format\n");
+			return -1;
+		}
+		if (CR50_BOARD_CFG_VALUE) {
+			if (first_access_this_boot())
+				cr50_set_board_cfg();
+		}
 	}
 	return 0;
 }
diff --git a/src/drivers/spi/tpm/tpm.h b/src/drivers/spi/tpm/tpm.h
index be98ed05df..b3e3f45ee9 100644
--- a/src/drivers/spi/tpm/tpm.h
+++ b/src/drivers/spi/tpm/tpm.h
@@ -41,4 +41,7 @@ size_t tpm2_process_command(const void *tpm2_command, size_t command_size,
 /* Get information about previously initialized TPM device. */
 void tpm2_get_info(struct tpm2_info *info);
 
+/* Indicates whether Cr50 ready pulses are guaranteed to be at least 100us. */
+bool cr50_is_long_interrupt_pulse_enabled(void);
+
 #endif  /* ! __COREBOOT_SRC_DRIVERS_SPI_TPM_TPM_H */
diff --git a/src/security/tpm/tss/vendor/cr50/Kconfig b/src/security/tpm/tss/vendor/cr50/Kconfig
index f606459d65..52c73859d8 100644
--- a/src/security/tpm/tss/vendor/cr50/Kconfig
+++ b/src/security/tpm/tss/vendor/cr50/Kconfig
@@ -12,4 +12,11 @@ config POWER_OFF_ON_CR50_UPDATE
 	help
 	  Power off machine while waiting for CR50 update to take effect.
 
+config CR50_USE_LONG_INTERRUPT_PULSES
+	bool
+	default n
+	help
+	  Whether to request longer interrupt pulses using Cr50 BOARD_CFG register.
+	  If the Cr50 firmware is too old, it will not be able to honor the request.
+
 endif