Re: [PATCH v4 2/2] tpm: add driver for cr50 on SPI

Jarkko Sakkinen
2016-08-09T10:20:37Z

On Thu, Jul 28, 2016 at 06:55:14PM -0700, Andrey Pronin wrote:
> 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>
> ---
> drivers/char/tpm/Kconfig | 9 ++
> drivers/char/tpm/Makefile | 1 +
> drivers/char/tpm/cr50_spi.c | 350 ++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 360 insertions(+)
> create mode 100644 drivers/char/tpm/cr50_spi.c
>
> diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
> index 9faa0b1..3320acc 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 Interface over SPI - Chips with Cr50 Firmware"
> + depends on SPI
> + select TCG_TIS_CORE
> + ---help---
> + If you have a chip 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 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..9cc1620
> --- /dev/null
> +++ b/drivers/char/tpm/cr50_spi.c
> @@ -0,0 +1,350 @@
> +/*
> + * 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 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/module.h>
> +#include <linux/wait.h>
> +#include <linux/of.h>
> +
> +#include <linux/module.h>
> +#include <linux/spi/spi.h>
> +#include <linux/tpm.h>
> +#include "tpm.h"
> +#include "tpm_tis_core.h"
> +
> +/*
> + * Cr50 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_SLEEP_DELAY_MSEC 1000
> +#define CR50_WAKE_START_DELAY_MSEC 60
> +#define CR50_ACCESS_DELAY_MSEC 2
> +
> +#define MAX_SPI_FRAMESIZE 64
> +
> +#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;
> +
> + u8 tx_buf[MAX_SPI_FRAMESIZE] ____cacheline_aligned;
> + u8 rx_buf[MAX_SPI_FRAMESIZE] ____cacheline_aligned;
> +};
> +
> +static 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.
> + */

"How to format kernel-doc comments" [1]

[1] https://www.kernel.org/doc/Documentation/kernel-documentation.rst

/Jarkko

> +static 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 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 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;
> + struct spi_transfer spi_xfer = {
> + .rx_buf = phy->rx_buf,
> + .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 (!(phy->rx_buf[0] & 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;
> + struct spi_transfer spi_xfer = {
> + .tx_buf = phy->tx_buf,
> + .rx_buf = phy->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);
> +
> + phy->tx_buf[0] = (do_write ? 0x00 : 0x80) | (len - 1);
> + phy->tx_buf[1] = 0xD4;
> + phy->tx_buf[2] = (addr >> 8) & 0xFF;
> + phy->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) {
> + memcpy(phy->tx_buf, buf, len);
> + spi_xfer.rx_buf = NULL;
> + } else {
> + spi_xfer.tx_buf = NULL;
> + }
> +
> + spi_message_init(&m);
> + spi_message_add_tail(&spi_xfer, &m);
> + ret = spi_sync_locked(phy->spi_device, &m);
> + if (!do_write)
> + memcpy(buf, phy->rx_buf, len);
> +
> +exit:
> + spi_bus_unlock(phy->spi_device->master);
> + 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;
> + __le16 le_val;
> +
> + rc = data->phy_ops->read_bytes(data, addr, sizeof(u16), (u8 *)&le_val);
> + if (!rc)
> + *result = le16_to_cpu(le_val);
> + return rc;
> +}
> +
> +static int cr50_spi_read32(struct tpm_tis_data *data, u32 addr, u32 *result)
> +{
> + int rc;
> + __le32 le_val;
> +
> + rc = data->phy_ops->read_bytes(data, addr, sizeof(u32), (u8 *)&le_val);
> + if (!rc)
> + *result = le32_to_cpu(le_val);
> + return rc;
> +}
> +
> +static int cr50_spi_write32(struct tpm_tis_data *data, u32 addr, u32 value)
> +{
> + __le32 le_val = cpu_to_le32(value);
> +
> + return data->phy_ops->write_bytes(data, addr, sizeof(u32),
> + (u8 *)&le_val);
> +}
> +
> +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 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;
> +}
> +
> +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,
> + .max_xfer_size = MAX_SPI_FRAMESIZE,
> +};
> +
> +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;
> +
> + phy = devm_kzalloc(&dev->dev, sizeof(struct cr50_spi_phy),
> + GFP_KERNEL);
> + if (!phy)
> + return -ENOMEM;
> +
> + phy->spi_device = dev;
> +
> + phy->access_delay_jiffies = CR50_ACCESS_DELAY_MSEC;
> + phy->sleep_delay_jiffies = CR50_SLEEP_DELAY_MSEC;
> + phy->wake_start_delay_msec = CR50_WAKE_START_DELAY_MSEC;
> +
> + 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", 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_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
>