/* * Copyright 2016 The Chromium OS Authors. All rights reserved. * Use of this source code is governed by a BSD-style license that can be * found in the LICENSE file. * * This is a driver for a SPI interfaced TPM2 device. * * It assumes that the required SPI interface has been initialized before the * driver is started. A 'sruct spi_slave' pointer passed at initialization is * used to direct traffic to the correct SPI interface. This dirver does not * provide a way to instantiate multiple TPM devices. Also, to keep things * simple, the driver unconditionally uses of TPM locality zero. * * References to documentation are based on the TCG issued "TPM Profile (PTP) * Specification Revision 00.43". */ #include #include #include #include #include #include #include #include #include #include "tpm.h" #define TPM_LOCALITY_0_SPI_BASE 0x00d40000 /* Assorted TPM2 registers for interface type FIFO. */ #define TPM_ACCESS_REG (TPM_LOCALITY_0_SPI_BASE + 0) #define TPM_STS_REG (TPM_LOCALITY_0_SPI_BASE + 0x18) #define TPM_DATA_FIFO_REG (TPM_LOCALITY_0_SPI_BASE + 0x24) #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_TIMEOUT_INIT_MS 30000 /* Very long timeout for TPM init */ /* SPI slave structure for TPM device. */ static struct spi_slave g_spi_slave CAR_GLOBAL; /* Cached TPM device identification. */ static struct tpm2_info g_tpm_info CAR_GLOBAL; /* * TODO(vbendeb): make CONFIG_DEBUG_TPM an int to allow different level of * debug traces. Right now it is either 0 or 1. */ static const int debug_level_ = CONFIG_DEBUG_TPM; /* * SPI frame header for TPM transactions is 4 bytes in size, it is described * in section "6.4.6 Spi Bit Protocol". */ typedef struct { unsigned char body[4]; } spi_frame_header; void tpm2_get_info(struct tpm2_info *info) { *info = car_get_var(g_tpm_info); } __weak int tis_plat_irq_status(void) { static int warning_displayed CAR_GLOBAL; if (!car_get_var(warning_displayed)) { printk(BIOS_WARNING, "WARNING: tis_plat_irq_status() not implemented, wasting 10ms to wait on Cr50!\n"); car_set_var(warning_displayed, 1); } mdelay(10); return 1; } /* * TPM may trigger a IRQ after finish processing previous transfer. * Waiting for this IRQ to sync TPM status. * * Returns 1 on success, 0 on failure (timeout). */ static int tpm_sync(void) { struct stopwatch sw; stopwatch_init_msecs_expire(&sw, 10); while (!tis_plat_irq_status()) { if (stopwatch_expired(&sw)) { printk(BIOS_ERR, "Timeout wait for TPM IRQ!\n"); return 0; } } return 1; } /* * Each TPM2 SPI transaction starts the same: CS is asserted, the 4 byte * header is sent to the TPM, the master waits til TPM is ready to continue. * * Returns 1 on success, 0 on failure (TPM SPI flow control timeout.) */ static int start_transaction(int read_write, size_t bytes, unsigned int addr) { spi_frame_header header; uint8_t byte; int i; struct stopwatch sw; static int tpm_sync_needed CAR_GLOBAL; static struct stopwatch wake_up_sw CAR_GLOBAL; struct spi_slave *spi_slave = car_get_var_ptr(&g_spi_slave); /* * First Cr50 access in each coreboot stage where TPM is used will be * prepended by a wake up pulse on the CS line. */ int wakeup_needed = 1; /* Wait for TPM to finish previous transaction if needed */ if (car_get_var(tpm_sync_needed)) { tpm_sync(); /* * During the first invocation of this function on each stage * this if () clause code does not run (as tpm_sync_needed * value is zero), during all following invocations the * stopwatch below is guaranteed to be started. */ if (!stopwatch_expired(car_get_var_ptr(&wake_up_sw))) wakeup_needed = 0; } else { car_set_var(tpm_sync_needed, 1); } if (wakeup_needed) { /* Just in case Cr50 is asleep. */ spi_claim_bus(spi_slave); udelay(1); spi_release_bus(spi_slave); udelay(100); } /* * The Cr50 on H1 does not go to sleep for 1 second after any * SPI slave activity, let's be conservative and limit the * window to 900 ms. */ stopwatch_init_msecs_expire(car_get_var_ptr(&wake_up_sw), 900); /* * The first byte of the frame header encodes the transaction type * (read or write) and transfer size (set to lentgh - 1), limited to * 64 bytes. */ header.body[0] = (read_write ? 0x80 : 0) | 0x40 | (bytes - 1); /* The rest of the frame header is the TPM register address. */ for (i = 0; i < 3; i++) header.body[i + 1] = (addr >> (8 * (2 - i))) & 0xff; /* CS assert wakes up the slave. */ spi_claim_bus(spi_slave); /* * The TCG TPM over SPI specification introduces the notion of SPI * flow control (Section "6.4.5 Flow Control"). * * Again, the slave (TPM device) expects each transaction to start * with a 4 byte header trasmitted by master. The header indicates if * the master needs to read or write a register, and the register * address. * * If the slave needs to stall the transaction (for instance it is not * ready to send the register value to the master), it sets the MOSI * line to 0 during the last clock of the 4 byte header. In this case * the master is supposed to start polling the SPI bus, one byte at * time, until the last bit in the received byte (transferred during * the last clock of the byte) is set to 1. * * Due to some SPI controllers' shortcomings (Rockchip comes to * mind...) we trasmit the 4 byte header without checking the byte * transmitted by the TPM during the transaction's last byte. * * We know that cr50 is guaranteed to set the flow control bit to 0 * during the header transfer, but real TPM2 might be fast enough not * to require to stall the master, this would present an issue. * crosbug.com/p/52132 has been opened to track this. */ spi_xfer(spi_slave, header.body, sizeof(header.body), NULL, 0); /* * Now poll the bus until TPM removes the stall bit. Give it up to 100 * ms to sort it out - it could be saving stuff in nvram at some * point. */ stopwatch_init_msecs_expire(&sw, 100); do { if (stopwatch_expired(&sw)) { printk(BIOS_ERR, "TPM flow control failure\n"); spi_release_bus(spi_slave); return 0; } spi_xfer(spi_slave, NULL, 0, &byte, 1); } while (!(byte & 1)); return 1; } /* * Print out the contents of a buffer, if debug is enabled. Skip registers * other than FIFO, unless debug_level_ is 2. */ static void trace_dump(const char *prefix, uint32_t reg, size_t bytes, const uint8_t *buffer, int force) { static char prev_prefix CAR_GLOBAL; static unsigned prev_reg CAR_GLOBAL; static int current_char CAR_GLOBAL; const int BYTES_PER_LINE = 32; int *current_char_ptr = car_get_var_ptr(¤t_char); if (!force) { if (!debug_level_) return; if ((debug_level_ < 2) && (reg != TPM_DATA_FIFO_REG)) return; } /* * Do not print register address again if the last dump print was for * that register. */ if ((car_get_var(prev_prefix) != *prefix) || (car_get_var(prev_reg) != reg)) { car_set_var(prev_prefix, *prefix); car_set_var(prev_reg, reg); printk(BIOS_DEBUG, "\n%s %2.2x:", prefix, reg); *current_char_ptr = 0; } if ((reg != TPM_DATA_FIFO_REG) && (bytes == 4)) { /* * This must be a regular register address, print the 32 bit * value. */ printk(BIOS_DEBUG, " %8.8x", *(const uint32_t *)buffer); } else { int i; /* * Data read from or written to FIFO or not in 4 byte * quantiites is printed byte at a time. */ for (i = 0; i < bytes; i++) { if (*current_char_ptr && !(*current_char_ptr % BYTES_PER_LINE)) { printk(BIOS_DEBUG, "\n "); *current_char_ptr = 0; } (*current_char_ptr)++; printk(BIOS_DEBUG, " %2.2x", buffer[i]); } } } /* * Once transaction is initiated and the TPM indicated that it is ready to go, * write the actual bytes to the register. */ static void write_bytes(const void *buffer, size_t bytes) { struct spi_slave *spi_slave = car_get_var_ptr(&g_spi_slave); spi_xfer(spi_slave, buffer, bytes, NULL, 0); } /* * Once transaction is initiated and the TPM indicated that it is ready to go, * read the actual bytes from the register. */ static void read_bytes(void *buffer, size_t bytes) { struct spi_slave *spi_slave = car_get_var_ptr(&g_spi_slave); spi_xfer(spi_slave, NULL, 0, buffer, bytes); } /* * To write a register, start transaction, transfer data to the TPM, deassert * CS when done. * * Returns one to indicate success, zero to indicate failure. */ static int tpm2_write_reg(unsigned int reg_number, const void *buffer, size_t bytes) { struct spi_slave *spi_slave = car_get_var_ptr(&g_spi_slave); trace_dump("W", reg_number, bytes, buffer, 0); if (!start_transaction(false, bytes, reg_number)) return 0; write_bytes(buffer, bytes); spi_release_bus(spi_slave); return 1; } /* * To read a register, start transaction, transfer data from the TPM, deassert * CS when done. * * Returns one to indicate success, zero to indicate failure. In case of * failure zero out the user buffer. */ static int tpm2_read_reg(unsigned int reg_number, void *buffer, size_t bytes) { struct spi_slave *spi_slave = car_get_var_ptr(&g_spi_slave); if (!start_transaction(true, bytes, reg_number)) { memset(buffer, 0, bytes); return 0; } read_bytes(buffer, bytes); spi_release_bus(spi_slave); trace_dump("R", reg_number, bytes, buffer, 0); return 1; } /* * Status register is accessed often, wrap reading and writing it into * dedicated functions. */ static int read_tpm_sts(uint32_t *status) { return tpm2_read_reg(TPM_STS_REG, status, sizeof(*status)); } static int write_tpm_sts(uint32_t status) { return tpm2_write_reg(TPM_STS_REG, &status, sizeof(status)); } /* * The TPM may limit the transaction bytes count (burst count) below the 64 * bytes max. The current value is available as a field of the status * register. */ static uint32_t get_burst_count(void) { uint32_t status; read_tpm_sts(&status); return (status & TPM_STS_BURST_COUNT_MASK) >> TPM_STS_BURST_COUNT_SHIFT; } static uint8_t tpm2_read_access_reg(void) { uint8_t access; tpm2_read_reg(TPM_ACCESS_REG, &access, sizeof(access)); /* We do not care about access establishment bit state. Ignore it. */ return access & ~TPM_ACCESS_ESTABLISHMENT; } static void tpm2_write_access_reg(uint8_t cmd) { /* Writes to access register can set only 1 bit at a time. */ assert (!(cmd & (cmd - 1))); tpm2_write_reg(TPM_ACCESS_REG, &cmd, sizeof(cmd)); } static int tpm2_claim_locality(void) { uint8_t access; struct stopwatch sw; /* * 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 { access = tpm2_read_access_reg(); if (access & TPM_ACCESS_ACTIVE_LOCALITY) { /* * Don't bombard the chip with traffic, let it keep * processing the command. */ mdelay(2); continue; } /* * Ok, the locality is free, TPM must be reset, let's claim * it. */ tpm2_write_access_reg(TPM_ACCESS_REQUEST_USE); access = tpm2_read_access_reg(); if (access != (TPM_ACCESS_VALID | TPM_ACCESS_ACTIVE_LOCALITY)) { break; } printk(BIOS_INFO, "TPM ready after %ld ms\n", stopwatch_duration_msecs(&sw)); return 1; } while (!stopwatch_expired(&sw)); printk(BIOS_ERR, "Failed to claim locality 0 after %ld ms, status: %#x\n", stopwatch_duration_msecs(&sw), access); return 0; } /* Device/vendor ID values of the TPM devices this driver supports. */ static const uint32_t supported_did_vids[] = { 0x00281ae0 /* H1 based Cr50 security chip. */ }; int tpm2_init(struct spi_slave *spi_if) { uint32_t did_vid, status; uint8_t cmd; int retries; struct tpm2_info *tpm_info = car_get_var_ptr(&g_tpm_info); struct spi_slave *spi_slave = car_get_var_ptr(&g_spi_slave); memcpy(spi_slave, spi_if, sizeof(*spi_if)); /* clear any pending IRQs */ tis_plat_irq_status(); /* * 150 ms should be enough to synchronize with the TPM even under the * worst nested reset request conditions. In vast majority of cases * there would be no wait at all. */ printk(BIOS_INFO, "Probing TPM: "); for (retries = 15; retries > 0; retries--) { int i; /* In case of failure to read div_vid is set to zero. */ tpm2_read_reg(TPM_DID_VID_REG, &did_vid, sizeof(did_vid)); for (i = 0; i < ARRAY_SIZE(supported_did_vids); i++) if (did_vid == supported_did_vids[i]) break; /* TPM is up and ready. */ if (i < ARRAY_SIZE(supported_did_vids)) break; /* TPM might be resetting, let's retry in a bit. */ mdelay(10); printk(BIOS_INFO, "."); } if (!retries) { printk(BIOS_ERR, "\n%s: Failed to connect to the TPM\n", __func__); return -1; } printk(BIOS_INFO, " done!\n"); if (ENV_VERSTAGE || ENV_BOOTBLOCK) /* * Claim locality 0, do it only during the first * initialization after reset. */ if (!tpm2_claim_locality()) return -1; read_tpm_sts(&status); if ((status & TPM_STS_FAMILY_MASK) != TPM_STS_FAMILY_TPM_2_0) { printk(BIOS_ERR, "unexpected TPM family value, status: %#x\n", status); return -1; } /* * Locality claimed, read the revision value and set up the tpm_info * structure. */ tpm2_read_reg(TPM_RID_REG, &cmd, sizeof(cmd)); tpm_info->vendor_id = did_vid & 0xffff; tpm_info->device_id = did_vid >> 16; tpm_info->revision = cmd; printk(BIOS_INFO, "Connected to device vid:did:rid of %4.4x:%4.4x:%2.2x\n", 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) { 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: "); /* * Does not really matter what's written, this just makes sure * the version is reported from the beginning. */ tpm2_write_reg(TPM_FW_VER, &chunk_size, 1); /* Print it out in sizeof(vstr) - 1 byte chunks. */ vstr[chunk_size] = 0; 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"); } return 0; } /* * This is in seconds, certain TPM commands, like key generation, can take * long time to complete. * * Returns one to indicate success, zero (not yet implemented) to indicate * failure. */ #define MAX_STATUS_TIMEOUT 120 static int wait_for_status(uint32_t status_mask, uint32_t status_expected) { uint32_t status; struct stopwatch sw; stopwatch_init_usecs_expire(&sw, MAX_STATUS_TIMEOUT * 1000 * 1000); do { udelay(1000); if (stopwatch_expired(&sw)) { printk(BIOS_ERR, "failed to get expected status %x\n", status_expected); return false; } read_tpm_sts(&status); } while ((status & status_mask) != status_expected); return 1; } enum fifo_transfer_direction { fifo_transmit = 0, fifo_receive = 1 }; /* Union allows to avoid casting away 'const' on transmit buffers. */ union fifo_transfer_buffer { uint8_t *rx_buffer; const uint8_t *tx_buffer; }; /* * Transfer requested number of bytes to or from TPM FIFO, accounting for the * current burst count value. */ static void fifo_transfer(size_t transfer_size, union fifo_transfer_buffer buffer, enum fifo_transfer_direction direction) { size_t transaction_size; size_t burst_count; size_t handled_so_far = 0; do { do { /* Could be zero when TPM is busy. */ burst_count = get_burst_count(); } while (!burst_count); transaction_size = transfer_size - handled_so_far; transaction_size = MIN(transaction_size, burst_count); /* * The SPI frame header does not allow to pass more than 64 * bytes. */ transaction_size = MIN(transaction_size, 64); if (direction == fifo_receive) tpm2_read_reg(TPM_DATA_FIFO_REG, buffer.rx_buffer + handled_so_far, transaction_size); else tpm2_write_reg(TPM_DATA_FIFO_REG, buffer.tx_buffer + handled_so_far, transaction_size); handled_so_far += transaction_size; } while (handled_so_far != transfer_size); } size_t tpm2_process_command(const void *tpm2_command, size_t command_size, void *tpm2_response, size_t max_response) { uint32_t status; uint32_t expected_status_bits; size_t payload_size; size_t bytes_to_go; const uint8_t *cmd_body = tpm2_command; uint8_t *rsp_body = tpm2_response; union fifo_transfer_buffer fifo_buffer; const int HEADER_SIZE = 6; struct tpm2_info *tpm_info = car_get_var_ptr(&g_tpm_info); /* Do not try using an uninitialized TPM. */ if (!tpm_info->vendor_id) return 0; /* Skip the two byte tag, read the size field. */ payload_size = read_be32(cmd_body + 2); /* Sanity check. */ if (payload_size != command_size) { printk(BIOS_ERR, "Command size mismatch: encoded %zd != requested %zd\n", payload_size, command_size); trace_dump("W", TPM_DATA_FIFO_REG, command_size, cmd_body, 1); printk(BIOS_DEBUG, "\n"); return 0; } /* Let the TPM know that the command is coming. */ write_tpm_sts(TPM_STS_COMMAND_READY); /* * TPM commands and responses written to and read from the FIFO * register (0x24) are datagrams of variable size, prepended by a 6 * byte header. * * The specification description of the state machine is a bit vague, * but from experience it looks like there is no need to wait for the * sts.expect bit to be set, at least with the 9670 and cr50 devices. * Just write the command into FIFO, making sure not to exceed the * burst count or the maximum PDU size, whatever is smaller. */ fifo_buffer.tx_buffer = cmd_body; fifo_transfer(command_size, fifo_buffer, fifo_transmit); /* Now tell the TPM it can start processing the command. */ write_tpm_sts(TPM_STS_GO); /* Now wait for it to report that the response is ready. */ expected_status_bits = TPM_STS_VALID | TPM_STS_DATA_AVAIL; if (!wait_for_status(expected_status_bits, expected_status_bits)) { /* * If timed out, which should never happen, let's at least * print out the offending command. */ trace_dump("W", TPM_DATA_FIFO_REG, command_size, cmd_body, 1); printk(BIOS_DEBUG, "\n"); return 0; } /* * The response is ready, let's read it. First we read the FIFO * payload header, to see how much data to expect. The response header * size is fixed to six bytes, the total payload size is stored in * network order in the last four bytes. */ tpm2_read_reg(TPM_DATA_FIFO_REG, rsp_body, HEADER_SIZE); /* Find out the total payload size, skipping the two byte tag. */ payload_size = read_be32(rsp_body + 2); if (payload_size > max_response) { /* * TODO(vbendeb): at least drain the FIFO here or somehow let * the TPM know that the response can be dropped. */ printk(BIOS_ERR, " TPM response too long (%zd bytes)", payload_size); return 0; } /* * Now let's read all but the last byte in the FIFO to make sure the * status register is showing correct flow control bits: 'more data' * until the last byte and then 'no more data' once the last byte is * read. */ bytes_to_go = payload_size - 1 - HEADER_SIZE; fifo_buffer.rx_buffer = rsp_body + HEADER_SIZE; fifo_transfer(bytes_to_go, fifo_buffer, fifo_receive); /* Verify that there is still data to read. */ read_tpm_sts(&status); if ((status & expected_status_bits) != expected_status_bits) { printk(BIOS_ERR, "unexpected intermediate status %#x\n", status); return 0; } /* Read the last byte of the PDU. */ tpm2_read_reg(TPM_DATA_FIFO_REG, rsp_body + payload_size - 1, 1); /* Terminate the dump, if enabled. */ if (debug_level_) printk(BIOS_DEBUG, "\n"); /* Verify that 'data available' is not asseretd any more. */ read_tpm_sts(&status); if ((status & expected_status_bits) != TPM_STS_VALID) { printk(BIOS_ERR, "unexpected final status %#x\n", status); return 0; } /* Move the TPM back to idle state. */ write_tpm_sts(TPM_STS_COMMAND_READY); return payload_size; }