Re: [PATCH v19 4/5] tpm: tpm_tis: Add tpm_tis_i2c driver
From: Jarkko Sakkinen
Date: Wed Nov 17 2021 - 03:19:28 EST
On Thu, 2021-11-04 at 16:02 +0200, amirmizi6@xxxxxxxxx wrote:
> From: Amir Mizinski <amirmizi6@xxxxxxxxx>
>
> I2C support for TPM devices on the TIS interface is currently available
> only as a proprietary driver implementation for each TPM vendor.
> This patch implements the infrastructure for a TCG-compliant TPM TIS I2C
> driver with the functionality required to communicate with a TPM device
> over I2C according to the "TCG PC Client PTP Interface Specification"
> and "Device Driver Design Principles for TPM 2.0"
>
> References:
> [1] "TCG PC Client Platform TPM Profile(PTP) Interface Specification for
> TPM 2.0" Version 01.03 Revision 22 at:
> https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
> [2] "TCG PC Client Device Driver Design Principles for TPM 2.0"
> Version 1.0 Revision 27 at:
> https://trustedcomputinggroup.org/resource/tcg-pc-client-device-driver-design-principles-for-tpm-2-0/
>
> Signed-off-by: Amir Mizinski <amirmizi6@xxxxxxxxx>
> Tested-by: Eddie James <eajames@xxxxxxxxxxxxx>
> Tested-by: Joel Stanley <joel@xxxxxxxxx>
> ---
> drivers/char/tpm/Kconfig | 12 ++
> drivers/char/tpm/Makefile | 1 +
> drivers/char/tpm/tpm_tis_i2c.c | 263 +++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 276 insertions(+)
> create mode 100644 drivers/char/tpm/tpm_tis_i2c.c
>
> diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
> index 4308f9c..4137ded 100644
> --- a/drivers/char/tpm/Kconfig
> +++ b/drivers/char/tpm/Kconfig
> @@ -86,6 +86,18 @@ config TCG_TIS_SYNQUACER
> To compile this driver as a module, choose M here;
> the module will be called tpm_tis_synquacer.
>
> +config TCG_TIS_I2C
> + tristate "TPM I2C Interface Specification"
> + depends on I2C
> + select CRC_CCITT
> + select TCG_TIS_CORE
> + help
> + If you have a TPM security chip, compliant with the TCG TPM PTP
> + (I2C interface) specification and connected to an I2C bus master,
> + 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 tpm_tis_i2c.
> +
> config TCG_TIS_I2C_CR50
> tristate "TPM Interface Specification 2.0 Interface (I2C - CR50)"
> depends on I2C
> diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
> index 66d39ea..0222b1d 100644
> --- a/drivers/char/tpm/Makefile
> +++ b/drivers/char/tpm/Makefile
> @@ -29,6 +29,7 @@ tpm_tis_spi-$(CONFIG_TCG_TIS_SPI_CR50) += tpm_tis_spi_cr50.o
>
> obj-$(CONFIG_TCG_TIS_I2C_CR50) += tpm_tis_i2c_cr50.o
>
> +obj-$(CONFIG_TCG_TIS_I2C) += tpm_tis_i2c.o
> obj-$(CONFIG_TCG_TIS_I2C_ATMEL) += tpm_i2c_atmel.o
> obj-$(CONFIG_TCG_TIS_I2C_INFINEON) += tpm_i2c_infineon.o
> obj-$(CONFIG_TCG_TIS_I2C_NUVOTON) += tpm_i2c_nuvoton.o
> diff --git a/drivers/char/tpm/tpm_tis_i2c.c b/drivers/char/tpm/tpm_tis_i2c.c
> new file mode 100644
> index 0000000..12984a3
> --- /dev/null
> +++ b/drivers/char/tpm/tpm_tis_i2c.c
> @@ -0,0 +1,263 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2014-2021 Nuvoton Technology corporation
> + *
> + * TPM TIS I2C Device Driver Interface for devices that implement the TPM
> + * I2C Interface defined by "TCG PC Client Platform TPM Profile (PTP)
> + * Specification version 01.05 r14" and "TCG PC Client Device Driver
> + * Design Principles version 1.0 r27" for TPM 2.0 at
> + * www.trustedcomputinggroup.org
> + */
> +
> +#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/acpi.h>
> +#include <linux/freezer.h>
> +
> +#include <linux/module.h>
> +#include <linux/i2c.h>
> +#include <linux/gpio.h>
> +#include <linux/of_irq.h>
> +#include <linux/of_gpio.h>
> +#include <linux/tpm.h>
> +#include "tpm_tis_core.h"
> +
> +#define TPM_LOC_SEL 0x04
> +#define TPM_I2C_INTERFACE_CAPABILITY 0x30
> +#define TPM_I2C_DEVICE_ADDRESS 0x38
> +#define TPM_DATA_CSUM_ENABLE 0x40
> +#define TPM_I2C_DID_VID 0x48
> +#define TPM_I2C_RID 0x4C
> +
> +struct tpm_tis_i2c_phy {
> + struct tpm_tis_data priv;
> + struct i2c_client *i2c_client;
> + u8 *iobuf;
> +};
> +
> +static inline struct tpm_tis_i2c_phy *to_tpm_tis_i2c_phy(struct tpm_tis_data *data)
> +{
> + return container_of(data, struct tpm_tis_i2c_phy, priv);
> +}
> +
> +static u8 address_to_register(u32 addr)
> +{
> + addr &= 0xFFF;
> +
> + switch (addr) {
> + // adapt register addresses that have changed compared to
> + // older TIS versions
C++ comment
> + case TPM_ACCESS(0):
> + return 0x04;
> + case TPM_LOC_SEL:
> + return 0x00;
> + case TPM_DID_VID(0):
> + return 0x48;
> + case TPM_RID(0):
> + return 0x4C;
> + default:
> + return addr;
> + }
> +}
> +
> +static int tpm_tis_i2c_read_bytes(struct tpm_tis_data *data, u32 addr, u16 len, u8 *result)
> +{
> + struct tpm_tis_i2c_phy *phy = to_tpm_tis_i2c_phy(data);
> + u8 reg = address_to_register(addr);
> + int ret;
> + int i = 0;
Declare i before ret (reverse Christmas tree order).
> + struct i2c_msg msgs[] = {
> + {
> + .addr = phy->i2c_client->addr,
> + .len = sizeof(reg),
> + .buf = ®,
> + },
> + {
> + .addr = phy->i2c_client->addr,
> + .len = len,
> + .buf = result,
> + .flags = I2C_M_RD,
> + },
> + };
> +
> + do {
> + ret = i2c_transfer(phy->i2c_client->adapter, msgs,
> + ARRAY_SIZE(msgs));
> + usleep_range(250, 300); // wait default GUARD_TIME of 250µs
So, what is this, and what is GUARD_TIME?
> +
> + } while (ret < 0 && i++ < TPM_RETRY);
> +
> + if (ret < 0)
> + return ret;
> +
> + return 0;
> +}
> +
> +static int tpm_tis_i2c_write_bytes(struct tpm_tis_data *data, u32 addr,
> + u16 len, const u8 *value)
> +{
> + struct tpm_tis_i2c_phy *phy = to_tpm_tis_i2c_phy(data);
> + int ret = 0;
> + int i = 0;
> +
> + if (phy->iobuf) {
> + if (len > TPM_BUFSIZE - 1)
> + return -EIO;
> +
> + phy->iobuf[0] = address_to_register(addr);
> + memcpy(phy->iobuf + 1, value, len);
> +
> + struct i2c_msg msgs[] = {
> + {
> + .addr = phy->i2c_client->addr,
> + .len = len + 1,
> + .buf = phy->iobuf,
> + },
> + };
> +
> + do {
> + ret = i2c_transfer(phy->i2c_client->adapter,
> + msgs, ARRAY_SIZE(msgs));
> + // wait default GUARD_TIME of 250µs
> + usleep_range(250, 300);
> + } while (ret < 0 && i++ < TPM_RETRY);
> + } else {
> + u8 reg = address_to_register(addr);
> +
> + struct i2c_msg msgs[] = {
> + {
> + .addr = phy->i2c_client->addr,
> + .len = sizeof(reg),
> + .buf = ®,
> + },
> + {
> + .addr = phy->i2c_client->addr,
> + .len = len,
> + .buf = (u8 *)value,
> + .flags = I2C_M_NOSTART,
> + },
> + };
> +
> + do {
> + ret = i2c_transfer(phy->i2c_client->adapter, msgs,
> + ARRAY_SIZE(msgs));
> + // wait default GUARD_TIME of 250µs
> + usleep_range(250, 300);
> + } while (ret < 0 && i++ < TPM_RETRY);
> + }
> +
> + if (ret < 0)
> + return ret;
> +
> + return 0;
> +}
> +
> +int tpm_tis_i2c_read16(struct tpm_tis_data *data, u32 addr, u16 *result)
> +{
> + __le16 result_le;
> + int rc;
> +
> + rc = data->phy_ops->read_bytes(data, addr, sizeof(u16),
> + (u8 *)&result_le);
> + if (!rc)
> + *result = le16_to_cpu(result_le);
> +
> + return rc;
> +}
> +
> +int tpm_tis_i2c_read32(struct tpm_tis_data *data, u32 addr, u32 *result)
> +{
> + __le32 result_le;
> + int rc;
> +
> + rc = data->phy_ops->read_bytes(data, addr, sizeof(u32),
> + (u8 *)&result_le);
> + if (!rc)
> + *result = le32_to_cpu(result_le);
> +
> + return rc;
> +}
> +
> +int tpm_tis_i2c_write32(struct tpm_tis_data *data, u32 addr, u32 value)
> +{
> + __le32 value_le;
> + int rc;
> +
> + value_le = cpu_to_le32(value);
> +
> + rc = data->phy_ops->write_bytes(data, addr, sizeof(u32),
> + (u8 *)&value_le);
> +
> + return rc;
> +}
> +
> +static SIMPLE_DEV_PM_OPS(tpm_tis_pm, tpm_pm_suspend, tpm_tis_resume);
> +
> +static const struct tpm_tis_phy_ops tpm_i2c_phy_ops = {
> + .read_bytes = tpm_tis_i2c_read_bytes,
> + .write_bytes = tpm_tis_i2c_write_bytes,
> + .read16 = tpm_tis_i2c_read16,
> + .read32 = tpm_tis_i2c_read32,
> + .write32 = tpm_tis_i2c_write32,
> +};
> +
> +static int tpm_tis_i2c_probe(struct i2c_client *dev, const struct i2c_device_id *id)
> +{
> + struct tpm_tis_i2c_phy *phy;
> + const u8 loc_init = 0;
> + int rc;
> +
> + phy = devm_kzalloc(&dev->dev, sizeof(struct tpm_tis_i2c_phy),
> + GFP_KERNEL);
> + if (!phy)
> + return -ENOMEM;
> +
> + phy->i2c_client = dev;
> +
> + if (!i2c_check_functionality(dev->adapter, I2C_FUNC_NOSTART)) {
> + phy->iobuf = devm_kmalloc(&dev->dev, TPM_BUFSIZE, GFP_KERNEL);
> + if (!phy->iobuf)
> + return -ENOMEM;
> + }
> +
> + /*select locality 0 (the driver will access only via locality 0)*/
Ugh
Please read these two carefully
- https://www.kernel.org/doc/html/latest/process/coding-style.html#commenting
- https://www.kernel.org/doc/html/latest/process/submitting-patches.html#style-check-your-changes
What non-obvious does this comment tell me?
> + rc = tpm_tis_i2c_write_bytes(&phy->priv, TPM_LOC_SEL, 1, &loc_init);
> + if (rc < 0)
> + return rc;
> +
> + return tpm_tis_core_init(&dev->dev, &phy->priv, -1, &tpm_i2c_phy_ops,
> + NULL);
> +}
> +
> +static const struct i2c_device_id tpm_tis_i2c_id[] = {
> + {"tpm_tis_i2c", 0},
> + {}
> +};
> +MODULE_DEVICE_TABLE(i2c, tpm_tis_i2c_id);
> +
> +static const struct of_device_id of_tis_i2c_match[] = {
> + { .compatible = "nuvoton,npct75x", },
> + { .compatible = "tcg,tpm-tis-i2c", },
> + {}
> +};
> +MODULE_DEVICE_TABLE(of, of_tis_i2c_match);
> +
> +static struct i2c_driver tpm_tis_i2c_driver = {
> + .driver = {
> + .owner = THIS_MODULE,
> + .name = "tpm_tis_i2c",
> + .pm = &tpm_tis_pm,
> + .of_match_table = of_match_ptr(of_tis_i2c_match),
> + },
> + .probe = tpm_tis_i2c_probe,
> + .id_table = tpm_tis_i2c_id,
> +};
> +
> +module_i2c_driver(tpm_tis_i2c_driver);
> +
> +MODULE_DESCRIPTION("TPM Driver");
> +MODULE_LICENSE("GPL");
/Jarkko