drivers/tpm/spi: Refactor out some cr50-specific logic

Mainboards accessing the cr50 over an I2C bus may want to reuse some of
the same firmware version and BOARD_CFG logic, therefore refactor this
logic out into a bus-agnostic file, drivers/tpm/cr50.c. This file uses
the new tis_vendor_read/write() functions in order to access the cr50
regardless of the bus which is physically used. In order to leave SPI
devices intact, the tis_vendor_* functions are added to the SPI driver.

BUG=b:202246591
TEST=boot to OS on google/dratini, see the same FW version and board_cfg
console prints as before the change.

Signed-off-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Change-Id: Ie68618cbe026a2b9221f93d0fe41d0b2054e8091
Reviewed-on: https://review.coreboot.org/c/coreboot/+/61977
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Subrata Banik <subratabanik@google.com>

src/drivers/tpm/Makefile.inc

@@ -5,3 +5,9 @@ ramstage-$(CONFIG_HAVE_ACPI_TABLES) += ppi.c
 else
 ramstage-$(CONFIG_HAVE_ACPI_TABLES) += ppi_stub.c
 endif
+
+bootblock-$(CONFIG_TPM_CR50) += cr50.c
+verstage-$(CONFIG_TPM_CR50) += cr50.c
+romstage-$(CONFIG_TPM_CR50) += cr50.c
+ramstage-$(CONFIG_TPM_CR50) += cr50.c
+postcar-$(CONFIG_TPM_CR50) += cr50.c

src/drivers/tpm/cr50.c

@@ -0,0 +1,195 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+
+#include <drivers/spi/tpm/tpm.h>
+#include <security/tpm/tis.h>
+#include <string.h>
+#include <types.h>
+
+#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)
+
+static struct cr50_firmware_version cr50_firmware_version;
+
+enum cr50_register {
+	CR50_FW_VER_REG,
+	CR50_BOARD_CFG_REG,
+};
+
+#define CR50_FW_VER_REG_SPI		(TPM_LOCALITY_0_SPI_BASE + 0xf90)
+#define CR50_BOARD_CFG_REG_SPI		(TPM_LOCALITY_0_SPI_BASE + 0xfe0)
+
+/* Return register address, which depends on the bus type, or -1 for error. */
+static int get_reg_addr(enum cr50_register reg)
+{
+	if (CONFIG(SPI_TPM)) {
+		switch (reg) {
+		case CR50_FW_VER_REG:
+			return CR50_FW_VER_REG_SPI;
+		case CR50_BOARD_CFG_REG:
+			return CR50_BOARD_CFG_REG_SPI;
+		default:
+			return -1;
+		}
+	}
+
+
+	return -1;
+}
+
+static bool 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 true;
+
+	printk(BIOS_INFO, "Cr50 firmware does not support CR50_BOARD_CFG, version: %d.%d.%d\n",
+	       version->epoch, version->major, version->minor);
+
+	return false;
+}
+
+/*
+ * 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 value;
+
+	if (!cr50_fw_supports_board_cfg(&cr50_firmware_version))
+		return 0;
+
+	const cb_err_t ret = tis_vendor_read(get_reg_addr(CR50_BOARD_CFG_REG), &value,
+					     sizeof(value));
+	if (ret != CB_SUCCESS) {
+		printk(BIOS_INFO, "Error reading from cr50\n");
+		return 0;
+	}
+
+	return value & CR50_BOARD_CFG_FEATUREBITS_MASK;
+}
+
+/**
+ * Set the BOARD_CFG register on the TPM chip to a particular compile-time constant value.
+ */
+cb_err_t cr50_set_board_cfg(void)
+{
+	uint32_t value;
+	cb_err_t ret;
+
+	if (!cr50_fw_supports_board_cfg(&cr50_firmware_version))
+		return CB_ERR;
+
+	/* Set the CR50_BOARD_CFG register, for e.g. asking cr50 to use longer ready pulses. */
+	ret = tis_vendor_read(get_reg_addr(CR50_BOARD_CFG_REG), &value, sizeof(value));
+	if (ret != CB_SUCCESS) {
+		printk(BIOS_INFO, "Error reading from cr50\n");
+		return CB_ERR;
+	}
+
+	if ((value & CR50_BOARD_CFG_FEATUREBITS_MASK) == CR50_BOARD_CFG_VALUE) {
+		printk(BIOS_INFO, "Current CR50_BOARD_CFG = 0x%08x, matches desired = 0x%08x\n",
+		       value, CR50_BOARD_CFG_VALUE);
+		return CB_SUCCESS;
+	}
+
+	if (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, "Current CR50_BOARD_CFG = 0x%08x, does not match"
+		       "desired = 0x%08x\n", value, CR50_BOARD_CFG_VALUE);
+		return CB_ERR;
+	}
+
+	printk(BIOS_INFO, "Current CR50_BOARD_CFG = 0x%08x, setting to 0x%08x\n",
+	       value, CR50_BOARD_CFG_VALUE);
+	value = CR50_BOARD_CFG_VALUE;
+
+	ret = tis_vendor_write(get_reg_addr(CR50_BOARD_CFG_REG), &value, sizeof(value));
+	if (ret != CB_SUCCESS) {
+		printk(BIOS_ERR, "Error writing to cr50\n");
+		return ret;
+	}
+
+	return CB_SUCCESS;
+}
+
+bool cr50_is_long_interrupt_pulse_enabled(void)
+{
+	return !!(cr50_get_board_cfg() & CR50_BOARD_CFG_100US_READY_PULSE);
+}
+
+static cb_err_t 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 CB_ERR_ARG;
+	number += 6; /* Skip past the colon. */
+
+	epoch = skip_atoi(&number);
+	if (*number++ != '.')
+		return CB_ERR_ARG;
+	major = skip_atoi(&number);
+	if (*number++ != '.')
+		return CB_ERR_ARG;
+	minor = skip_atoi(&number);
+
+	ver->epoch = epoch;
+	ver->major = major;
+	ver->minor = minor;
+	return CB_SUCCESS;
+}
+
+cb_err_t cr50_get_firmware_version(struct cr50_firmware_version *version)
+{
+	if (cr50_firmware_version.epoch || cr50_firmware_version.major ||
+	    cr50_firmware_version.minor)
+		goto success;
+
+	int chunk_count = 0;
+	size_t chunk_size = 50;
+	char version_str[301];
+	int addr = get_reg_addr(CR50_FW_VER_REG);
+
+	/*
+	 * Does not really matter what's written, this just makes sure
+	 * the version is reported from the beginning.
+	 */
+	tis_vendor_write(addr, &chunk_size, 1);
+
+	/*
+	 * Read chunk_size bytes at a time, last chunk will be zero padded.
+	 */
+	do {
+		uint8_t *buf = (uint8_t *)version_str + chunk_count * chunk_size;
+		tis_vendor_read(addr, buf, 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) != CB_SUCCESS) {
+		printk(BIOS_ERR, "Did not recognize Cr50 version format\n");
+		return CB_ERR;
+	}
+
+success:
+	*version = cr50_firmware_version;
+	return CB_SUCCESS;
+}

src/drivers/tpm/cr50.h

@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+
+#ifndef __DRIVERS_TPM_CR50_H__
+#define __DRIVERS_TPM_CR50_H__
+
+#include <types.h>
+
+/* Structure describing the elements of Cr50 firmware version. */
+struct cr50_firmware_version {
+	int epoch;
+	int major;
+	int minor;
+};
+
+/* Indicates whether Cr50 ready pulses are guaranteed to be at least 100us. */
+bool cr50_is_long_interrupt_pulse_enabled(void);
+
+/* Get the Cr50 firmware version information. */
+cb_err_t cr50_get_firmware_version(struct cr50_firmware_version *version);
+
+/* Set the BOARD_CFG register depending on Cr50 Kconfigs */
+cb_err_t cr50_set_board_cfg(void);
+
+#endif /* __DRIVERS_TPM_CR50_H__ */