[PATCH v4 6/6] tpm: add driver for cr50 on SPI

Stephen Boyd
2019-08-12T22:36:38Z

From: Andrey Pronin <apronin@chromium.org>

Add TPM2.0 PTP FIFO compatible SPI interface for chips with Cr50
firmware. The firmware running on the currently supported H1
Secure Microcontroller requires a special driver to handle its
specifics:

- need to ensure a certain delay between spi transactions, or else
the chip may miss some part of the next transaction;
- if there is no spi activity for some time, it may go to sleep,
and needs to be waken up before sending further commands;
- access to vendor-specific registers.

Signed-off-by: Andrey Pronin <apronin@chromium.org>
Cc: Andrey Pronin <apronin@chromium.org>
Cc: Duncan Laurie <dlaurie@chromium.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Alexander Steffen <Alexander.Steffen@infineon.com>
[swboyd@chromium.org: Replace boilerplate with SPDX tag, drop
suspended bit and remove ifdef checks in cr50.h, push tpm.h
include into cr50.c, migrate to functions exported from tpm_tis_spi.h]
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
---
drivers/char/tpm/Kconfig | 9 +
drivers/char/tpm/Makefile | 1 +
drivers/char/tpm/cr50_spi.c | 372 ++++++++++++++++++++++++++++++++++++
3 files changed, 382 insertions(+)
create mode 100644 drivers/char/tpm/cr50_spi.c

diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
index 88a3c06fc153..1fb23f145ef6 100644
--- a/drivers/char/tpm/Kconfig
+++ b/drivers/char/tpm/Kconfig
@@ -114,6 +114,15 @@ config TCG_ATMEL
will be accessible from within Linux. To compile this driver
as a module, choose M here; the module will be called tpm_atmel.

+config TCG_CR50_SPI
+ tristate "Cr50 SPI Interface"
+ depends on TCG_TIS_SPI
+ ---help---
+ If you have a H1 secure module running Cr50 firmware on SPI bus,
+ say Yes and it will be accessible from within Linux. To compile
+ this driver as a module, choose M here; the module will be called
+ cr50_spi.
+
config TCG_INFINEON
tristate "Infineon Technologies TPM Interface"
depends on PNP
diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
index a01c4cab902a..4713e52ce1b0 100644
--- a/drivers/char/tpm/Makefile
+++ b/drivers/char/tpm/Makefile
@@ -27,6 +27,7 @@ obj-$(CONFIG_TCG_TIS_I2C_INFINEON) += tpm_i2c_infineon.o
obj-$(CONFIG_TCG_TIS_I2C_NUVOTON) += tpm_i2c_nuvoton.o
obj-$(CONFIG_TCG_NSC) += tpm_nsc.o
obj-$(CONFIG_TCG_ATMEL) += tpm_atmel.o
+obj-$(CONFIG_TCG_CR50_SPI) += cr50_spi.o
obj-$(CONFIG_TCG_INFINEON) += tpm_infineon.o
obj-$(CONFIG_TCG_IBMVTPM) += tpm_ibmvtpm.o
obj-$(CONFIG_TCG_TIS_ST33ZP24) += st33zp24/
diff --git a/drivers/char/tpm/cr50_spi.c b/drivers/char/tpm/cr50_spi.c
new file mode 100644
index 000000000000..a163864e9c63
--- /dev/null
+++ b/drivers/char/tpm/cr50_spi.c
@@ -0,0 +1,372 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2016 Google, Inc
+ *
+ * This device driver implements a TCG PTP FIFO interface over SPI for chips
+ * with Cr50 firmware.
+ * It is based on tpm_tis_spi driver by Peter Huewe and Christophe Ricard.
+ */
+
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/pm.h>
+#include <linux/spi/spi.h>
+#include <linux/wait.h>
+
+#include "tpm_tis_core.h"
+#include "tpm_tis_spi.h"
+
+/*
+ * Cr50 timing constants:
+ * - can go to sleep not earlier than after CR50_SLEEP_DELAY_MSEC.
+ * - needs up to CR50_WAKE_START_DELAY_USEC to wake after sleep.
+ * - requires waiting for "ready" IRQ, if supported; or waiting for at least
+ * CR50_NOIRQ_ACCESS_DELAY_MSEC between transactions, if IRQ is not supported.
+ * - waits for up to CR50_FLOW_CONTROL for flow control 'ready' indication.
+ */
+#define CR50_SLEEP_DELAY_MSEC 1000
+#define CR50_WAKE_START_DELAY_USEC 1000
+#define CR50_NOIRQ_ACCESS_DELAY msecs_to_jiffies(2)
+#define CR50_READY_IRQ_TIMEOUT msecs_to_jiffies(TPM2_TIMEOUT_A)
+#define CR50_FLOW_CONTROL msecs_to_jiffies(TPM2_TIMEOUT_A)
+#define MAX_IRQ_CONFIRMATION_ATTEMPTS 3
+
+#define TPM_CR50_FW_VER(l) (0x0f90 | ((l) << 12))
+#define TPM_CR50_MAX_FW_VER_LEN 64
+
+struct cr50_spi_phy {
+ struct tpm_tis_spi_phy spi_phy;
+
+ struct mutex time_track_mutex;
+ unsigned long last_access;
+ unsigned long wake_after;
+
+ unsigned long access_delay;
+
+ struct completion ready;
+
+ unsigned int irq_confirmation_attempt;
+ bool irq_needs_confirmation;
+ bool irq_confirmed;
+};
+
+static inline struct cr50_spi_phy *to_cr50_spi_phy(struct tpm_tis_spi_phy *phy)
+{
+ return container_of(phy, struct cr50_spi_phy, spi_phy);
+}
+
+/*
+ * The cr50 interrupt handler just signals waiting threads that the
+ * interrupt was asserted. It does not do any processing triggered
+ * by interrupts but is instead used to avoid fixed delays.
+ */
+static irqreturn_t cr50_spi_irq_handler(int dummy, void *dev_id)
+{
+ struct cr50_spi_phy *cr50_phy = dev_id;
+
+ cr50_phy->irq_confirmed = true;
+ complete(&cr50_phy->ready);
+
+ return IRQ_HANDLED;
+}
+
+/*
+ * Cr50 needs to have at least some delay between consecutive
+ * transactions. Make sure we wait.
+ */
+static void cr50_ensure_access_delay(struct cr50_spi_phy *phy)
+{
+ unsigned long allowed_access = phy->last_access + phy->access_delay;
+ unsigned long time_now = jiffies;
+ struct device *dev = &phy->spi_phy.spi_device->dev;
+
+ /*
+ * Note: There is a small chance, if Cr50 is not accessed in a few days,
+ * that time_in_range will not provide the correct result after the wrap
+ * around for jiffies. In this case, we'll have an unneeded short delay,
+ * which is fine.
+ */
+ if (time_in_range_open(time_now, phy->last_access, allowed_access)) {
+ unsigned long remaining, timeout = allowed_access - time_now;
+
+ remaining = wait_for_completion_timeout(&phy->ready, timeout);
+ if (!remaining && phy->irq_confirmed)
+ dev_warn(dev, "Timeout waiting for TPM ready IRQ\n");
+ }
+
+ if (phy->irq_needs_confirmation) {
+ unsigned int attempt = ++phy->irq_confirmation_attempt;
+
+ if (phy->irq_confirmed) {
+ phy->irq_needs_confirmation = false;
+ phy->access_delay = CR50_READY_IRQ_TIMEOUT;
+ dev_info(dev, "TPM ready IRQ confirmed on attempt %u\n",
+ attempt);
+ } else if (attempt > MAX_IRQ_CONFIRMATION_ATTEMPTS) {
+ phy->irq_needs_confirmation = false;
+ dev_warn(dev, "IRQ not confirmed - will use delays\n");
+ }
+ }
+}
+
+/*
+ * Cr50 might go to sleep if there is no SPI activity for some time and
+ * miss the first few bits/bytes on the bus. In such case, wake it up
+ * by asserting CS and give it time to start up.
+ */
+static bool cr50_needs_waking(struct cr50_spi_phy *phy)
+{
+ /*
+ * Note: There is a small chance, if Cr50 is not accessed in a few days,
+ * that time_in_range will not provide the correct result after the wrap
+ * around for jiffies. In this case, we'll probably timeout or read
+ * incorrect value from TPM_STS and just retry the operation.
+ */
+ return !time_in_range_open(jiffies, phy->last_access, phy->wake_after);
+}
+
+static void cr50_wake_if_needed(struct cr50_spi_phy *cr50_phy)
+{
+ struct tpm_tis_spi_phy *phy = &cr50_phy->spi_phy;
+
+ if (cr50_needs_waking(cr50_phy)) {
+ /* Assert CS, wait 1 msec, deassert CS */
+ struct spi_transfer spi_cs_wake = { .delay_usecs = 1000 };
+
+ spi_sync_transfer(phy->spi_device, &spi_cs_wake, 1);
+ /* Wait for it to fully wake */
+ usleep_range(CR50_WAKE_START_DELAY_USEC,
+ CR50_WAKE_START_DELAY_USEC * 2);
+ }
+
+ /* Reset the time when we need to wake Cr50 again */
+ cr50_phy->wake_after = jiffies + msecs_to_jiffies(CR50_SLEEP_DELAY_MSEC);
+}
+
+/*
+ * Flow control: clock the bus and wait for cr50 to set LSB before
+ * sending/receiving data. TCG PTP spec allows it to happen during
+ * the last byte of header, but cr50 never does that in practice,
+ * and earlier versions had a bug when it was set too early, so don't
+ * check for it during header transfer.
+ */
+static int cr50_spi_flow_control(struct tpm_tis_spi_phy *phy,
+ struct spi_transfer *spi_xfer)
+{
+ struct device *dev = &phy->spi_device->dev;
+ unsigned long timeout = jiffies + CR50_FLOW_CONTROL;
+ struct spi_message m;
+ int ret;
+
+ spi_xfer->len = 1;
+
+ do {
+ spi_message_init(&m);
+ spi_message_add_tail(spi_xfer, &m);
+ ret = spi_sync_locked(phy->spi_device, &m);
+ if (ret < 0)
+ return ret;
+
+ if (time_after(jiffies, timeout)) {
+ dev_warn(dev, "Timeout during flow control\n");
+ return -EBUSY;
+ }
+ } while (!(phy->iobuf[0] & 0x01));
+
+ return 0;
+}
+
+static void cr50_spi_reinit_completion(struct tpm_tis_spi_phy *phy)
+{
+ struct cr50_spi_phy *cr50_phy = to_cr50_spi_phy(phy);
+ reinit_completion(&cr50_phy->ready);
+}
+
+static int tpm_tis_spi_cr50_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
+ u8 *in, const u8 *out)
+{
+ struct tpm_tis_spi_phy *phy = to_tpm_tis_spi_phy(data);
+ struct cr50_spi_phy *cr50_phy = to_cr50_spi_phy(phy);
+ int ret;
+
+ mutex_lock(&cr50_phy->time_track_mutex);
+ /*
+ * Do this outside of spi_bus_lock in case cr50 is not the
+ * only device on that spi bus.
+ */
+ cr50_ensure_access_delay(cr50_phy);
+ cr50_wake_if_needed(cr50_phy);
+
+ ret = tpm_tis_spi_transfer(data, addr, len, in, out);
+
+ cr50_phy->last_access = jiffies;
+ mutex_unlock(&cr50_phy->time_track_mutex);
+
+ return ret;
+}
+
+static int tpm_tis_spi_cr50_read_bytes(struct tpm_tis_data *data, u32 addr,
+ u16 len, u8 *result)
+{
+ return tpm_tis_spi_cr50_transfer(data, addr, len, result, NULL);
+}
+
+static int tpm_tis_spi_cr50_write_bytes(struct tpm_tis_data *data, u32 addr,
+ u16 len, const u8 *value)
+{
+ return tpm_tis_spi_cr50_transfer(data, addr, len, NULL, value);
+}
+
+static const struct tpm_tis_phy_ops tpm_spi_cr50_phy_ops = {
+ .read_bytes = tpm_tis_spi_cr50_read_bytes,
+ .write_bytes = tpm_tis_spi_cr50_write_bytes,
+ .read16 = tpm_tis_spi_read16,
+ .read32 = tpm_tis_spi_read32,
+ .write32 = tpm_tis_spi_write32,
+};
+
+static void cr50_print_fw_version(struct tpm_tis_data *data)
+{
+ struct tpm_tis_spi_phy *phy = to_tpm_tis_spi_phy(data);
+ int i, len = 0;
+ char fw_ver[TPM_CR50_MAX_FW_VER_LEN + 1];
+ char fw_ver_block[4];
+
+ /*
+ * Write anything to TPM_CR50_FW_VER to start from the beginning
+ * of the version string
+ */
+ tpm_tis_write8(data, TPM_CR50_FW_VER(data->locality), 0);
+
+ /* Read the string, 4 bytes at a time, until we get '\0' */
+ do {
+ tpm_tis_read_bytes(data, TPM_CR50_FW_VER(data->locality), 4,
+ fw_ver_block);
+ for (i = 0; i < 4 && fw_ver_block[i]; ++len, ++i)
+ fw_ver[len] = fw_ver_block[i];
+ } while (i == 4 && len < TPM_CR50_MAX_FW_VER_LEN);
+ fw_ver[len] = '\0';
+
+ dev_info(&phy->spi_device->dev, "Cr50 firmware version: %s\n", fw_ver);
+}
+
+static int cr50_spi_probe(struct spi_device *spi)
+{
+ struct tpm_tis_spi_phy *phy;
+ struct cr50_spi_phy *cr50_phy;
+ int ret;
+ struct tpm_chip *chip;
+
+ cr50_phy = devm_kzalloc(&spi->dev, sizeof(*cr50_phy), GFP_KERNEL);
+ if (!cr50_phy)
+ return -ENOMEM;
+
+ phy = &cr50_phy->spi_phy;
+ phy->flow_control = cr50_spi_flow_control;
+ phy->pre_transfer = cr50_spi_reinit_completion;
+
+ cr50_phy->access_delay = CR50_NOIRQ_ACCESS_DELAY;
+
+ mutex_init(&cr50_phy->time_track_mutex);
+ cr50_phy->wake_after = jiffies;
+ cr50_phy->last_access = jiffies;
+
+ init_completion(&cr50_phy->ready);
+ if (spi->irq > 0) {
+ ret = devm_request_irq(&spi->dev, spi->irq, cr50_spi_irq_handler,
+ IRQF_TRIGGER_RISING | IRQF_ONESHOT,
+ "cr50_spi", cr50_phy);
+ if (ret < 0) {
+ if (ret == -EPROBE_DEFER)
+ return ret;
+ dev_warn(&spi->dev, "Requesting IRQ %d failed: %d\n",
+ spi->irq, ret);
+ /*
+ * This is not fatal, the driver will fall back to
+ * delays automatically, since ready will never
+ * be completed without a registered irq handler.
+ * So, just fall through.
+ */
+ } else {
+ /*
+ * IRQ requested, let's verify that it is actually
+ * triggered, before relying on it.
+ */
+ cr50_phy->irq_needs_confirmation = true;
+ }
+ } else {
+ dev_warn(&spi->dev,
+ "No IRQ - will use delays between transactions.\n");
+ }
+
+ ret = tpm_tis_spi_init(spi, phy, -1, &tpm_spi_cr50_phy_ops);
+ if (ret)
+ return ret;
+
+ cr50_print_fw_version(&phy->priv);
+
+ chip = dev_get_drvdata(&spi->dev);
+ chip->flags |= TPM_CHIP_FLAG_FIRMWARE_POWER_MANAGED;
+
+ return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int cr50_spi_resume(struct device *dev)
+{
+ struct tpm_chip *chip = dev_get_drvdata(dev);
+ struct tpm_tis_data *data = dev_get_drvdata(&chip->dev);
+ struct tpm_tis_spi_phy *phy = to_tpm_tis_spi_phy(data);
+ struct cr50_spi_phy *cr50_phy = to_cr50_spi_phy(phy);
+
+ /*
+ * Jiffies not increased during suspend, so we need to reset
+ * the time to wake Cr50 after resume.
+ */
+ cr50_phy->wake_after = jiffies;
+
+ return tpm_tis_resume(dev);
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(cr50_spi_pm, tpm_pm_suspend, cr50_spi_resume);
+
+static int cr50_spi_remove(struct spi_device *dev)
+{
+ struct tpm_chip *chip = spi_get_drvdata(dev);
+
+ tpm_chip_unregister(chip);
+ tpm_tis_remove(chip);
+ return 0;
+}
+
+static const struct spi_device_id cr50_spi_id[] = {
+ { "cr50", 0 },
+ {}
+};
+MODULE_DEVICE_TABLE(spi, cr50_spi_id);
+
+#ifdef CONFIG_OF
+static const struct of_device_id of_cr50_spi_match[] = {
+ { .compatible = "google,cr50", },
+ {}
+};
+MODULE_DEVICE_TABLE(of, of_cr50_spi_match);
+#endif
+
+static struct spi_driver cr50_spi_driver = {
+ .driver = {
+ .name = "cr50_spi",
+ .pm = &cr50_spi_pm,
+ .of_match_table = of_match_ptr(of_cr50_spi_match),
+ },
+ .probe = cr50_spi_probe,
+ .remove = cr50_spi_remove,
+ .id_table = cr50_spi_id,
+};
+module_spi_driver(cr50_spi_driver);
+
+MODULE_DESCRIPTION("Cr50 TCG PTP FIFO SPI driver");
+MODULE_LICENSE("GPL v2");
--
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