[PATCH 2/2] tpm: add driver for cr50 on SPI

Andrey Pronin
2016-07-15T02:21:05Z

Add TCG TPM2.0 PTP FIFO compatible interface for Cr50 chip on SPI bus.

Signed-off-by: Andrey Pronin <apronin@chromium.org>
---
drivers/char/tpm/Kconfig | 9 +
drivers/char/tpm/Makefile | 1 +
drivers/char/tpm/cr50_spi.c | 409 ++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 419 insertions(+)
create mode 100644 drivers/char/tpm/cr50_spi.c

diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
index 9faa0b1..6773a06 100644
--- a/drivers/char/tpm/Kconfig
+++ b/drivers/char/tpm/Kconfig
@@ -100,6 +100,15 @@ 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 "TCG PTP FIFO Compliant Interface over SPI for Cr50"
+ depends on SPI
+ select TCG_TIS_CORE
+ ---help---
+ If you have a Cr50 chip 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 a385fb8..b346306 100644
--- a/drivers/char/tpm/Makefile
+++ b/drivers/char/tpm/Makefile
@@ -20,6 +20,7 @@ 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 0000000..0672434
--- /dev/null
+++ b/drivers/char/tpm/cr50_spi.c
@@ -0,0 +1,409 @@
+/*
+ * Copyright (C) 2016 Google, Inc
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2, as published by
+ * the Free Software Foundation.
+ *
+ * This device driver implements a TCG PTP FIFO compliant interface over SPI
+ * for Cr50 devices.
+ * It is based on cr50_spi driver by Peter Huewe and Christophe Ricard.
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/slab.h>
+#include <linux/interrupt.h>
+#include <linux/wait.h>
+#include <linux/freezer.h>
+
+#include <linux/module.h>
+#include <linux/spi/spi.h>
+#include <linux/gpio.h>
+#include <linux/of_irq.h>
+#include <linux/of_gpio.h>
+#include <linux/tpm.h>
+#include "tpm.h"
+#include "tpm_tis_core.h"
+
+#define MAX_SPI_FRAMESIZE 64
+
+/* Cr50 default timing constants:
+ * - can go to sleep not earlier than after CR50_SLEEP_DELAY_MSEC
+ * - needs up to CR50_WAKE_START_DELAY_MSEC to wake after sleep
+ * - requires at least CR50_ACCESS_DELAY_MSEC between transactions
+ */
+#define CR50_DFT_SLEEP_DELAY_MSEC 1000
+#define CR50_DFT_WAKE_START_DELAY_MSEC 60
+#define CR50_DFT_ACCESS_DELAY_MSEC 2
+
+#define TPM_CR50_FW_VER(l) (0x0F90 | ((l) << 12))
+#define TPM_CR50_MAX_FW_VER_LEN 64
+
+struct cr50_spi_phy {
+ struct tpm_tis_data priv;
+ struct spi_device *spi_device;
+
+ struct mutex time_track_mutex;
+ unsigned long last_access_jiffies;
+ unsigned long wake_after_jiffies;
+
+ unsigned long access_delay_jiffies;
+ unsigned long sleep_delay_jiffies;
+ unsigned int wake_start_delay_msec;
+};
+
+static inline struct cr50_spi_phy *to_cr50_spi_phy(struct tpm_tis_data *data)
+{
+ return container_of(data, struct cr50_spi_phy, priv);
+}
+
+/* Cr50 needs to have at least some delay between consecutive
+ * transactions. Make sure we wait.
+ */
+static inline void cr50_ensure_access_delay(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 have an unneeded short delay,
+ * which is fine.
+ */
+ unsigned long allowed_access =
+ phy->last_access_jiffies + phy->access_delay_jiffies;
+ unsigned long time_now = jiffies;
+
+ if (time_in_range_open(time_now,
+ phy->last_access_jiffies, allowed_access))
+ mdelay(jiffies_to_msecs(allowed_access - time_now));
+}
+
+/* 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 inline 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_jiffies,
+ phy->wake_after_jiffies);
+}
+static inline void cr50_wake_if_needed(struct cr50_spi_phy *phy)
+{
+ if (cr50_needs_waking(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 */
+ msleep(phy->wake_start_delay_msec);
+ }
+ /* Reset the time when we need to wake Cr50 again */
+ phy->wake_after_jiffies = jiffies + phy->sleep_delay_jiffies;
+}
+
+/* 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 cr50_spi_phy *phy)
+{
+ unsigned long timeout_jiffies =
+ jiffies + msecs_to_jiffies(TPM_RETRY * TPM_TIMEOUT_RETRY);
+ struct spi_message m;
+ int ret;
+ u8 rx = 0;
+ struct spi_transfer spi_xfer = {
+ .rx_buf = &rx,
+ .len = 1,
+ .cs_change = 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_jiffies))
+ return -EBUSY;
+ } while (!(rx & 0x01));
+ return 0;
+}
+
+static int cr50_spi_xfer_bytes(struct tpm_tis_data *data, u32 addr,
+ u16 len, u8 *buf, bool do_write)
+{
+ struct cr50_spi_phy *phy = to_cr50_spi_phy(data);
+ struct spi_message m;
+ u8 tx_buf[4];
+ u8 rx_buf[4];
+ struct spi_transfer spi_xfer = {
+ .tx_buf = tx_buf,
+ .rx_buf = rx_buf,
+ .len = 4,
+ .cs_change = 1,
+ };
+ int ret;
+
+ if (len > MAX_SPI_FRAMESIZE)
+ return -EINVAL;
+
+ /* Do this outside of spi_bus_lock in case cr50 is not the
+ * only device on that spi bus.
+ */
+ mutex_lock(&phy->time_track_mutex);
+ cr50_ensure_access_delay(phy);
+ cr50_wake_if_needed(phy);
+ mutex_unlock(&phy->time_track_mutex);
+
+ tx_buf[0] = (do_write ? 0x00 : 0x80) | (len - 1);
+ tx_buf[1] = 0xD4;
+ tx_buf[2] = (addr >> 8) & 0xFF;
+ tx_buf[3] = addr & 0xFF;
+
+ spi_message_init(&m);
+ spi_message_add_tail(&spi_xfer, &m);
+
+ spi_bus_lock(phy->spi_device->master);
+ ret = spi_sync_locked(phy->spi_device, &m);
+ if (ret < 0)
+ goto exit;
+
+ ret = cr50_spi_flow_control(phy);
+ if (ret < 0)
+ goto exit;
+
+ spi_xfer.cs_change = 0;
+ spi_xfer.len = len;
+ if (do_write) {
+ spi_xfer.tx_buf = buf;
+ spi_xfer.rx_buf = NULL;
+ } else {
+ spi_xfer.tx_buf = NULL;
+ spi_xfer.rx_buf = buf;
+ }
+
+ spi_message_init(&m);
+ spi_message_add_tail(&spi_xfer, &m);
+ ret = spi_sync_locked(phy->spi_device, &m);
+
+exit:
+ spi_bus_unlock(phy->spi_device->master);
+
+ mutex_lock(&phy->time_track_mutex);
+ phy->last_access_jiffies = jiffies;
+ mutex_unlock(&phy->time_track_mutex);
+
+ return ret;
+}
+
+static int cr50_spi_read_bytes(struct tpm_tis_data *data, u32 addr,
+ u16 len, u8 *result)
+{
+ return cr50_spi_xfer_bytes(data, addr, len, result, false);
+}
+
+static int cr50_spi_write_bytes(struct tpm_tis_data *data, u32 addr,
+ u16 len, u8 *value)
+{
+ return cr50_spi_xfer_bytes(data, addr, len, value, true);
+}
+
+static int cr50_spi_read16(struct tpm_tis_data *data, u32 addr, u16 *result)
+{
+ int rc;
+
+ rc = data->phy_ops->read_bytes(data, addr, sizeof(u16), (u8 *)result);
+ if (!rc)
+ *result = le16_to_cpu(*result);
+ return rc;
+}
+
+static int cr50_spi_read32(struct tpm_tis_data *data, u32 addr, u32 *result)
+{
+ int rc;
+
+ rc = data->phy_ops->read_bytes(data, addr, sizeof(u32), (u8 *)result);
+ if (!rc)
+ *result = le32_to_cpu(*result);
+ return rc;
+}
+
+static int cr50_spi_write32(struct tpm_tis_data *data, u32 addr, u32 value)
+{
+ value = cpu_to_le32(value);
+ return data->phy_ops->write_bytes(data, addr, sizeof(u32),
+ (u8 *)&value);
+}
+
+static void cr50_get_fw_version(struct tpm_tis_data *data, char *fw_ver)
+{
+ int i, len = 0;
+ char fw_ver_block[4];
+
+ /* Write anything to TPM_CR50_FW_VER to start from the beg of 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]; )
+ fw_ver[len++] = fw_ver_block[i++];
+ } while (i == 4 && len < TPM_CR50_MAX_FW_VER_LEN);
+ fw_ver[len] = 0;
+}
+
+static ssize_t fw_version_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ char fw_ver[TPM_CR50_MAX_FW_VER_LEN+1];
+ struct tpm_tis_data *data = dev_get_drvdata(dev);
+
+ cr50_get_fw_version(data, fw_ver);
+ return sprintf(buf, "%s\n", fw_ver);
+}
+static DEVICE_ATTR_RO(fw_version);
+
+static struct attribute *cr50_attrs[] = {
+ &dev_attr_fw_version.attr,
+ NULL,
+};
+
+static const struct attribute_group cr50_attr_group = {
+ .attrs = cr50_attrs,
+};
+
+static const struct tpm_tis_phy_ops cr50_spi_phy_ops = {
+ .read_bytes = cr50_spi_read_bytes,
+ .write_bytes = cr50_spi_write_bytes,
+ .read16 = cr50_spi_read16,
+ .read32 = cr50_spi_read32,
+ .write32 = cr50_spi_write32,
+ .attr_group = &cr50_attr_group,
+ .max_xfer_size = MAX_SPI_FRAMESIZE,
+};
+
+static int cr50_of_property_read_u32_optional(struct spi_device *dev,
+ const char *name,
+ u32 default_value,
+ u32 *value)
+{
+ struct device_node *np = dev->dev.of_node;
+ int rc;
+
+ if (of_find_property(np, name, NULL)) {
+ rc = of_property_read_u32(np, name, value);
+ if (rc < 0) {
+ dev_err(&dev->dev,
+ "invalid '%s' property (%d)\n",
+ name, rc);
+ return rc;
+ }
+ } else {
+ *value = default_value;
+ }
+
+ dev_dbg(&dev->dev, "%s = %u\n", name, *value);
+ return 0;
+}
+
+static int cr50_spi_probe(struct spi_device *dev)
+{
+ char fw_ver[TPM_CR50_MAX_FW_VER_LEN+1];
+ struct cr50_spi_phy *phy;
+ int rc;
+ u32 value;
+
+ phy = devm_kzalloc(&dev->dev, sizeof(struct cr50_spi_phy),
+ GFP_KERNEL);
+ if (!phy)
+ return -ENOMEM;
+
+ phy->spi_device = dev;
+
+ /* Cr50 timing properties.
+ */
+ rc = cr50_of_property_read_u32_optional(dev, "access-delay-msec",
+ CR50_DFT_ACCESS_DELAY_MSEC,
+ &value);
+ if (rc < 0)
+ return rc;
+ phy->access_delay_jiffies = msecs_to_jiffies(value);
+
+ rc = cr50_of_property_read_u32_optional(dev, "sleep-delay-msec",
+ CR50_DFT_SLEEP_DELAY_MSEC,
+ &value);
+ if (rc < 0)
+ return rc;
+ phy->sleep_delay_jiffies = msecs_to_jiffies(value);
+
+ rc = cr50_of_property_read_u32_optional(dev, "wake-start-delay-msec",
+ CR50_DFT_WAKE_START_DELAY_MSEC,
+ &value);
+ if (rc < 0)
+ return rc;
+ phy->wake_start_delay_msec = value;
+
+ mutex_init(&phy->time_track_mutex);
+ phy->wake_after_jiffies = jiffies;
+ phy->last_access_jiffies = jiffies;
+
+ rc = tpm_tis_core_init(&dev->dev, &phy->priv, -1, &cr50_spi_phy_ops,
+ NULL);
+ if (rc < 0)
+ return rc;
+
+ cr50_get_fw_version(&phy->priv, fw_ver);
+ dev_info(&dev->dev, "Cr50 firmware version: %s\n", fw_ver);
+
+ return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(cr50_pm, tpm_pm_suspend, tpm_tis_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_spi", 0},
+ {}
+};
+MODULE_DEVICE_TABLE(spi, cr50_spi_id);
+
+static const struct of_device_id of_cr50_spi_match[] = {
+ { .compatible = "google,cr50_spi", },
+ {}
+};
+MODULE_DEVICE_TABLE(of, of_cr50_spi_match);
+
+static struct spi_driver cr50_spi_driver = {
+ .driver = {
+ .owner = THIS_MODULE,
+ .name = "cr50_spi",
+ .pm = &cr50_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");
--
2.6.6