Message-ID: <7132-5e553800-15-d29cca0@16308930>
Date:   Tue, 25 Feb 2020 15:07:16 +0000
From:   "Helen Mae Koike Fornazier" <koike@...labora.com>
To:     "Fabien Lahoudere" <fabien.lahoudere@...labora.com>
Cc:     swboyd@...omium.org, kernel@...labora.com,
        "Duncan Laurie" <dlaurie@...omium.org>,
        "Peter Huewe" <peterhuewe@....de>,
        "Jarkko Sakkinen" <jarkko.sakkinen@...ux.intel.com>,
        "Jason Gunthorpe" <jgg@...pe.ca>, "Arnd Bergmann" <arnd@...db.de>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, linux-integrity@...r.kernel.org
Subject: Re: [PATCH 1/1] tpm: Add driver for cr50 on I2C

Hi Fabien,

I'm not familiar with this subsystem, but I was scanning through the
code and saw some small (not that important) nits.

Please, see below.

On 2/25/20 8:12 AM, Fabien Lahoudere wrote:
> From: Duncan Laurie <dlaurie@...omium.org>
>       Stephen Boyd <swboyd@...omium.org>
> 
> Add TPM 2.0 compatible I2C interface for chips with cr50 firmware.
> 
> The firmware running on the currently supported H1 MCU requires a
> special driver to handle its specific protocol, and this makes it
> unsuitable to use tpm_tis_core_* and instead it must implement the
> underlying TPM protocol similar to the other I2C TPM drivers.
> 
> - All 4 byes of status register must be read/written at once.
> - FIFO and burst count is limited to 63 and must be drained by AP.
> - Provides an interrupt to indicate when read response data is ready
> and when the TPM is finished processing write data.
> 
> This driver is based on the existing infineon I2C TPM driver, which
> most closely matches the cr50 i2c protocol behavior.  The driver is
> intentionally kept very similar in structure and style to the
> corresponding drivers in coreboot and depthcharge.
> 
> Signed-off-by: Duncan Laurie <dlaurie@...omium.org>
> [swboyd@...omium.org: Depend on i2c even if it's a module, replace
> boilier plate with SPDX tag, drop asm/byteorder.h include, simplify
> return from probe]
> Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> Signed-off-by: Fabien Lahoudere <fabien.lahoudere@...labora.com>
> ---
>  drivers/char/tpm/Kconfig            |  10 +
>  drivers/char/tpm/Makefile           |   2 +
>  drivers/char/tpm/tpm_tis_i2c_cr50.c | 765 ++++++++++++++++++++++++++++
>  3 files changed, 777 insertions(+)
>  create mode 100644 drivers/char/tpm/tpm_tis_i2c_cr50.c
> 
> diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
> index aacdeed93320..4b8e60118891 100644
> --- a/drivers/char/tpm/Kconfig
> +++ b/drivers/char/tpm/Kconfig
> @@ -74,6 +74,16 @@ config TCG_TIS_SPI_CR50
>  	  If you have a H1 secure module running Cr50 firmware on SPI bus,
>  	  say Yes and it will be accessible from within Linux.
>  
> +config TCG_TIS_I2C_CR50
> +	tristate "TPM Interface Specification 2.0 Interface (I2C - CR50)"
> +	depends on I2C
> +	select TCG_CR50
> +	help
> +	  This is a driver for the Google cr50 I2C TPM interface which is a
> +	  custom microcontroller and requires a custom i2c protocol interface
> +	  to handle the limitations of the hardware.  To compile this driver
> +	  as a module, choose M here; the module will be called tcg_tis_i2c_cr50.
> +
>  config TCG_TIS_I2C_ATMEL
>  	tristate "TPM Interface Specification 1.2 Interface (I2C - Atmel)"
>  	depends on I2C
> diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
> index 9567e5197f74..68d96410c1fb 100644
> --- a/drivers/char/tpm/Makefile
> +++ b/drivers/char/tpm/Makefile
> @@ -26,6 +26,8 @@ obj-$(CONFIG_TCG_TIS_SPI) += tpm_tis_spi.o
>  tpm_tis_spi-y := tpm_tis_spi_main.o
>  tpm_tis_spi-$(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_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_cr50.c b/drivers/char/tpm/tpm_tis_i2c_cr50.c
> new file mode 100644
> index 000000000000..ed9bcb7b8bc1
> --- /dev/null
> +++ b/drivers/char/tpm/tpm_tis_i2c_cr50.c
> @@ -0,0 +1,765 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright 2016 Google Inc.
> + *
> + * Based on Linux Kernel TPM driver by
> + * Peter Huewe <peter.huewe@...ineon.com>
> + * Copyright (C) 2011 Infineon Technologies
> + */
> +
> +/*
> + * cr50 is a firmware for H1 secure modules that requires special
> + * handling for the I2C interface.
> + *
> + * - Use an interrupt for transaction status instead of hardcoded delays
> + * - Must use write+wait+read read protocol
> + * - All 4 bytes of status register must be read/written at once
> + * - Burst count max is 63 bytes, and burst count behaves
> + *   slightly differently than other I2C TPMs
> + * - When reading from FIFO the full burstcnt must be read
> + *   instead of just reading header and determining the remainder
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/completion.h>
> +#include <linux/i2c.h>
> +#include <linux/module.h>
> +#include <linux/pm.h>
> +#include <linux/slab.h>
> +#include <linux/interrupt.h>

no sorted alfabetically.

> +#include <linux/wait.h>
> +#include "tpm_tis_core.h"
> +
> +#define CR50_MAX_BUFSIZE	63
> +#define CR50_TIMEOUT_SHORT_MS	2	/* Short timeout during transactions */
> +#define CR50_TIMEOUT_NOIRQ_MS	20	/* Timeout for TPM ready without IRQ */
> +#define CR50_I2C_DID_VID	0x00281ae0L
> +#define CR50_I2C_MAX_RETRIES	3	/* Max retries due to I2C errors */
> +#define CR50_I2C_RETRY_DELAY_LO	55	/* Min usecs between retries on I2C */
> +#define CR50_I2C_RETRY_DELAY_HI	65	/* Max usecs between retries on I2C */
> +
> +#define TPM_I2C_ACCESS(l)	(0x0000 | ((l) << 4))
> +#define TPM_I2C_STS(l)		(0x0001 | ((l) << 4))
> +#define TPM_I2C_DATA_FIFO(l)	(0x0005 | ((l) << 4))
> +#define TPM_I2C_DID_VID(l)	(0x0006 | ((l) << 4))
> +
> +struct priv_data {
> +	int irq;
> +	int locality;
> +	struct completion tpm_ready;
> +	u8 buf[CR50_MAX_BUFSIZE + sizeof(u8)];

I was wondering why you need + sizeof(u8) here.

> +};
> +
> +/*
> + * 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.
> + *
> + * @dummy: unuesed parameter
> + * @dev_id: TPM chip information
> + */
> +static irqreturn_t cr50_i2c_int_handler(int dummy, void *dev_id)
> +{
> +	struct tpm_chip *chip = dev_id;
> +	struct priv_data *priv = dev_get_drvdata(&chip->dev);
> +
> +	complete(&priv->tpm_ready);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +/*
> + * Wait for completion interrupt if available, otherwise use a fixed
> + * delay for the TPM to be ready.
> + *
> + * @chip: TPM chip information
> + *
> + * Returns negative number for error, positive number for success.

Maybe just add a comment that return 0 means timeout.

> + */
> +static int cr50_i2c_wait_tpm_ready(struct tpm_chip *chip)
> +{
> +	struct priv_data *priv = dev_get_drvdata(&chip->dev);
> +	long rc;
> +
> +	/* Use a safe fixed delay if interrupt is not supported */
> +	if (priv->irq <= 0) {
> +		msleep(CR50_TIMEOUT_NOIRQ_MS);
> +		return 1;
> +	}
> +
> +	/* Wait for interrupt to indicate TPM is ready to respond */
> +	rc = wait_for_completion_timeout(&priv->tpm_ready,
> +					 msecs_to_jiffies(chip->timeout_a));
> +
> +	if (rc == 0)

I usually use (!rc), but I see that infinion uses (rc == 0) style.

> +		dev_warn(&chip->dev, "Timeout waiting for TPM ready\n");
> +
> +	return rc;
> +}
> +
> +/*
> + * cr50_i2c_enable_tpm_irq - enable TPM irq
> + *
> + * @chip: TPM chip information
> + */
> +static void cr50_i2c_enable_tpm_irq(struct tpm_chip *chip)
> +{
> +	struct priv_data *priv = dev_get_drvdata(&chip->dev);
> +
> +	if (priv->irq > 0) {
> +		reinit_completion(&priv->tpm_ready);
> +		enable_irq(priv->irq);
> +	}
> +}
> +
> +/*
> + * cr50_i2c_disable_tpm_irq - disable TPM irq
> + *
> + * @chip: TPM chip information
> + */
> +static void cr50_i2c_disable_tpm_irq(struct tpm_chip *chip)
> +{
> +	struct priv_data *priv = dev_get_drvdata(&chip->dev);
> +
> +	if (priv->irq > 0)
> +		disable_irq(priv->irq);
> +}
> +
> +/*
> + * cr50_i2c_transfer - transfer messages over i2c
> + *
> + * @dev: device information
> + * @adapter: i2c adapter
> + * @msgs: array of messages to transfer
> + * @num: number of messages in the array

I see that num is always 1 in the rest of the code.
Maybe instead of receiving an array, you could receive a
single message.

And rename the function to
static int cr50_i2c_transfer_message(struct device *dev, struct i2c_adapter *adapter,
			     struct i2c_msg *msg);

> + *
> + * Call unlocked i2c transfer routine with the provided parameters and retry
> + * in case of bus errors. Returns the number of transferred messages.
> + */
> +static int cr50_i2c_transfer(struct device *dev, struct i2c_adapter *adapter,
> +			     struct i2c_msg *msgs, int num)
> +{
> +	int rc, try;

unsigned int try

> +
> +	for (try = 0; try < CR50_I2C_MAX_RETRIES; try++) {
> +		rc = __i2c_transfer(adapter, msgs, num);

Maybe you should check if num < 1 (in case you decide to keep this parameter),
otherwise this will loop for no reason.

> +		if (rc > 0)
> +			break;
> +		if (try)
> +			dev_warn(dev, "i2c transfer failed (attempt %d/%d): %d\n",
> +				 try + 1, CR50_I2C_MAX_RETRIES, rc);
> +		usleep_range(CR50_I2C_RETRY_DELAY_LO, CR50_I2C_RETRY_DELAY_HI);
> +	}
> +
> +	return rc;
> +}
> +
> +/*
> + * cr50_i2c_read() - read from TPM register
> + *
> + * @chip: TPM chip information
> + * @addr: register address to read from
> + * @buffer: provided by caller
> + * @len: number of bytes to read
> + *
> + * 1) send register address byte 'addr' to the TPM
> + * 2) wait for TPM to indicate it is ready
> + * 3) read 'len' bytes of TPM response into the provided 'buffer'
> + *
> + * Returns negative number for error, 0 for success.
> + */
> +static int cr50_i2c_read(struct tpm_chip *chip, u8 addr, u8 *buffer, size_t len)
> +{
> +	struct i2c_client *client = to_i2c_client(chip->dev.parent);
> +	struct i2c_msg msg1 = {
> +		.addr = client->addr,
> +		.len = 1,
> +		.buf = &addr
> +	};
> +	struct i2c_msg msg2 = {
> +		.addr = client->addr,
> +		.flags = I2C_M_RD,
> +		.len = len,
> +		.buf = buffer
> +	};
> +	int rc;
> +
> +	i2c_lock_bus(client->adapter, I2C_LOCK_SEGMENT);
> +
> +	/* Prepare for completion interrupt */
> +	cr50_i2c_enable_tpm_irq(chip);
> +
> +	/* Send the register address byte to the TPM */
> +	rc = cr50_i2c_transfer(&chip->dev, client->adapter, &msg1, 1);> +	if (rc <= 0)
> +		goto out;
> +
> +	/* Wait for TPM to be ready with response data */
> +	rc = cr50_i2c_wait_tpm_ready(chip);
> +	if (rc < 0)
> +		goto out;
> +
> +	/* Read response data from the TPM */
> +	rc = cr50_i2c_transfer(&chip->dev, client->adapter, &msg2, 1);> +
> +out:
> +	cr50_i2c_disable_tpm_irq(chip);
> +	i2c_unlock_bus(client->adapter, I2C_LOCK_SEGMENT);
> +
> +	if (rc < 0)
> +		return rc;
> +	if (rc == 0)
> +		return -EIO; /* No i2c segments transferred */
> +
> +	return 0;

If you don't prevent this function from returning a positive number,
you can save a few lines with just:

	if (rc == 0)
		return -EIO; /* No i2c segments transferred */

	return rc;

> +}
> +
> +/*
> + * cr50_i2c_write() - write to TPM register
> + *
> + * @chip: TPM chip information
> + * @addr: register address to write to
> + * @buffer: data to write
> + * @len: number of bytes to write
> + *
> + * 1) prepend the provided address to the provided data
> + * 2) send the address+data to the TPM
> + * 3) wait for TPM to indicate it is done writing
> + *
> + * Returns negative number for error, 0 for success.
> + */
> +static int cr50_i2c_write(struct tpm_chip *chip, u8 addr, u8 *buffer,
> +			  size_t len)
> +{
> +	struct priv_data *priv = dev_get_drvdata(&chip->dev);
> +	struct i2c_client *client = to_i2c_client(chip->dev.parent);
> +	struct i2c_msg msg1 = {
> +		.addr = client->addr,
> +		.len = len + 1,
> +		.buf = priv->buf
> +	};
> +	int rc;
> +
> +	if (len > CR50_MAX_BUFSIZE)
> +		return -EINVAL;
> +
> +	i2c_lock_bus(client->adapter, I2C_LOCK_SEGMENT);
> +
> +	/* Prepend the 'register address' to the buffer */
> +	priv->buf[0] = addr;
> +	memcpy(priv->buf + 1, buffer, len);
> +
> +	/* Prepare for completion interrupt */
> +	cr50_i2c_enable_tpm_irq(chip);
> +
> +	/* Send write request buffer with address */
> +	rc = cr50_i2c_transfer(&chip->dev, client->adapter, &msg1, 1);> +	if (rc <= 0)
> +		goto out;
> +
> +	/* Wait for TPM to be ready, ignore timeout */
> +	cr50_i2c_wait_tpm_ready(chip);
> +
> +out:
> +	cr50_i2c_disable_tpm_irq(chip);
> +	i2c_unlock_bus(client->adapter, I2C_LOCK_SEGMENT);
> +
> +	if (rc < 0)
> +		return rc;
> +	if (rc == 0)
> +		return -EIO; /* No i2c segments transferred */
> +
> +	return 0;

same here

> +}
> +
> +/*
> + * check_locality - verify TPM locality
> + *
> + * @chip: TPM chip information
> + *
> + * Returns negative number for error, 0 for success.
> + */
> +static int check_locality(struct tpm_chip *chip)

maybe the locality function could also be prefixed with cr50_
I see that infineon doesn't prefix them, but wich a prefix it is
easier to see this is a local function.

> +{
> +	u8 mask = TPM_ACCESS_VALID | TPM_ACCESS_ACTIVE_LOCALITY;
> +	u8 buf;
> +	int rc;
> +
> +	rc = cr50_i2c_read(chip, TPM_I2C_ACCESS(0), &buf, 1);

Maybe sizeof(buf)? (just to keep the standard)
It is also clearer what the last parameter means.

Same comment for other usages of this function and also cr50_i2c_write()
in the rest of the code.

> +	if (rc < 0)
> +		return rc;
> +
> +	if ((buf & mask) == mask)
> +		return 0;
> +
> +	return -EIO;
> +}
> +
> +/*
> + * release_locality - release TPM locality
> + *
> + * @chip: TPM chip information
> + * @force: flag to force release if set
> + */
> +static void release_locality(struct tpm_chip *chip, int force)

I was wondering if "force" couldn't be an enum instead of int.
It is easier to read

release_locality(chip, CR50_FORCE);
release_locality(chip, CR50_NO_FORCE);

compared to:

release_locality(chip, 1);
release_locality(chip, 0);

> +{
> +	struct priv_data *priv = dev_get_drvdata(&chip->dev);
> +	u8 mask = TPM_ACCESS_VALID | TPM_ACCESS_REQUEST_PENDING;
> +	u8 addr = TPM_I2C_ACCESS(priv->locality);
> +	u8 buf;
> +
> +	if (cr50_i2c_read(chip, addr, &buf, 1) < 0)
> +		return;
> +
> +	if (force || (buf & mask) == mask) {
> +		buf = TPM_ACCESS_ACTIVE_LOCALITY;
> +		cr50_i2c_write(chip, addr, &buf, 1);
> +	}
> +
> +	priv->locality = 0;
> +}
> +
> +/*
> + * request_locality - request TPM locality
> + *
> + * @chip: TPM chip information
> + */
> +static int request_locality(struct tpm_chip *chip)
> +{
> +	struct priv_data *priv = dev_get_drvdata(&chip->dev);
> +	u8 buf = TPM_ACCESS_REQUEST_USE;
> +	unsigned long stop;
> +	int rc;
> +
> +	if (check_locality(chip) == 0)
> +		return 0;
> +
> +	rc = cr50_i2c_write(chip, TPM_I2C_ACCESS(0), &buf, 1);
> +	if (rc < 0)
> +		return rc;
> +
> +	stop = jiffies + chip->timeout_a;
> +	do {
> +		if (check_locality(chip) == 0) {
> +			priv->locality = 0;> +			return 0;
> +		}

Shouldn't priv->locality be set to 1 in some part of the code?
it seems that priv->locality is always zero (unless I'm missing something).


> +		msleep(CR50_TIMEOUT_SHORT_MS);
> +	} while (time_before(jiffies, stop));
> +
> +	return -ETIMEDOUT;
> +}
> +
> +/*
> + * cr50 requires all 4 bytes of status register to be read
> + *
> + * @chip: TPM chip information
> + *
> + * Returns TPM status
> + */
> +static u8 cr50_i2c_tis_status(struct tpm_chip *chip)
> +{
> +	struct priv_data *priv = dev_get_drvdata(&chip->dev);
> +	u8 buf[4];
> +
> +	if (cr50_i2c_read(chip, TPM_I2C_STS(priv->locality),
> +			  buf, sizeof(buf)) < 0)
> +		return 0;
> +	return buf[0];
> +}
> +
> +/*
> + * cr50 requires all 4 bytes of status register to be written
> + *
> + * @chip: TPM chip information
> + */
> +static void cr50_i2c_tis_ready(struct tpm_chip *chip)
> +{
> +	struct priv_data *priv = dev_get_drvdata(&chip->dev);
> +	u8 buf[4] = { TPM_STS_COMMAND_READY };
> +
> +	cr50_i2c_write(chip, TPM_I2C_STS(priv->locality), buf, sizeof(buf));
> +	msleep(CR50_TIMEOUT_SHORT_MS);
> +}
> +
> +/*
> + * cr50 uses bytes 3:2 of status register for burst count and
> + * all 4 bytes must be read
> + *
> + * @chip: TPM chip information
> + * @mask: status mask
> + * @burst: return value for burst
> + * @status: return value for statis
> + *
> + * Returns negative number for error, 0 for success.
> + */
> +static int cr50_i2c_wait_burststs(struct tpm_chip *chip, u8 mask,
> +				  size_t *burst, int *status)
> +{
> +	struct priv_data *priv = dev_get_drvdata(&chip->dev);
> +	unsigned long stop;
> +	u8 buf[4];
> +
> +	/* wait for burstcount */
> +	stop = jiffies + chip->timeout_b;
> +	do {
> +		if (cr50_i2c_read(chip, TPM_I2C_STS(priv->locality),
> +				  (u8 *)&buf, sizeof(buf)) < 0) {

I think you can remove this (u8 *)& cast

> +			msleep(CR50_TIMEOUT_SHORT_MS);
> +			continue;
> +		}
> +
> +		*status = *buf;
> +		*burst = le16_to_cpup((__le16 *)(buf + 1));
> +
> +		if ((*status & mask) == mask &&
> +		    *burst > 0 && *burst <= CR50_MAX_BUFSIZE)
> +			return 0;
> +
> +		msleep(CR50_TIMEOUT_SHORT_MS);
> +	} while (time_before(jiffies, stop));
> +
> +	dev_err(&chip->dev, "Timeout reading burst and status\n");
> +	return -ETIMEDOUT;
> +}
> +
> +/*
> + * cr50_i2c_tis_recv - TPM reception callback
> + *
> + * @chip: TPM chip information
> + * @buf: reception buffer
> + * @buf_len: buffer length to read
> + *
> + * Returns negative number for error, number of bytes read for success.
> + */
> +static int cr50_i2c_tis_recv(struct tpm_chip *chip, u8 *buf, size_t buf_len)
> +{
> +	struct priv_data *priv = dev_get_drvdata(&chip->dev);
> +	int status, rc;
> +	size_t burstcnt, cur, len, expected;
> +	u8 addr = TPM_I2C_DATA_FIFO(priv->locality);
> +	u8 mask = TPM_STS_VALID | TPM_STS_DATA_AVAIL;
> +
> +	if (buf_len < TPM_HEADER_SIZE)
> +		return -EINVAL;

I see infinion returns -EIO, I was wondering if you shouldn't do the same here.
I also wonder if you shouldn't have a goto out_err to abort any current transaction
if still pending.

> +
> +	rc = cr50_i2c_wait_burststs(chip, mask, &burstcnt, &status);
> +	if (rc < 0)
> +		goto out_err;
> +
> +	if (burstcnt > buf_len || burstcnt < TPM_HEADER_SIZE) {
> +		dev_err(&chip->dev,
> +			"Unexpected burstcnt: %zu (max=%zu, min=%d)\n",
> +			burstcnt, buf_len, TPM_HEADER_SIZE);
> +		rc = -EIO;
> +		goto out_err;
> +	}
> +
> +	/* Read first chunk of burstcnt bytes */
> +	rc = cr50_i2c_read(chip, addr, buf, burstcnt);
> +	if (rc < 0) {
> +		dev_err(&chip->dev, "Read of first chunk failed\n");
> +		goto out_err;
> +	}
> +
> +	/* Determine expected data in the return buffer */
> +	expected = be32_to_cpup((__be32 *)(buf + 2));
> +	if (expected > buf_len) {
> +		dev_err(&chip->dev, "Too much data in FIFO\n");

I was confused with this message.
Maybe:
"Provided buffer is too small to receive data from i2c"

> +		goto out_err;
> +	}
> +
> +	/* Now read the rest of the data */
> +	cur = burstcnt;
> +	while (cur < expected) {
> +		/* Read updated burst count and check status */
> +		rc = cr50_i2c_wait_burststs(chip, mask, &burstcnt, &status);
> +		if (rc < 0)
> +			goto out_err;
> +
> +		len = min_t(size_t, burstcnt, expected - cur);
> +		rc = cr50_i2c_read(chip, addr, buf + cur, len);
> +		if (rc < 0) {
> +			dev_err(&chip->dev, "Read failed\n");
> +			goto out_err;
> +		}
> +
> +		cur += len;
> +	}
> +
> +	/* Ensure TPM is done reading data */
> +	rc = cr50_i2c_wait_burststs(chip, TPM_STS_VALID, &burstcnt, &status);
> +	if (rc < 0)
> +		goto out_err;
> +	if (status & TPM_STS_DATA_AVAIL) {
> +		dev_err(&chip->dev, "Data still available\n");

I was wondering if this is that bad to fail. But I see infineon does the same.



I hope this helps

Regards,
Helen

> +		rc = -EIO;
> +		goto out_err;
> +	}
> +
> +	release_locality(chip, 0);
> +	return cur;
> +
> +out_err:
> +	/* Abort current transaction if still pending */
> +	if (cr50_i2c_tis_status(chip) & TPM_STS_COMMAND_READY)
> +		cr50_i2c_tis_ready(chip);
> +
> +	release_locality(chip, 0);
> +	return rc;
> +}
> +
> +/*
> + * cr50_i2c_tis_send - TPM emission callback
> + *
> + * @chip: TPM chip information
> + * @buf: buffer to send
> + * @len: buffer length
> + *
> + * Returns negative number for error, 0 for success.
> + */
> +static int cr50_i2c_tis_send(struct tpm_chip *chip, u8 *buf, size_t len)
> +{
> +	struct priv_data *priv = dev_get_drvdata(&chip->dev);
> +	int rc, status;
> +	size_t burstcnt, limit, sent = 0;
> +	u8 tpm_go[4] = { TPM_STS_GO };
> +	unsigned long stop;
> +
> +	rc = request_locality(chip);
> +	if (rc < 0)
> +		return rc;
> +
> +	/* Wait until TPM is ready for a command */
> +	stop = jiffies + chip->timeout_b;
> +	while (!(cr50_i2c_tis_status(chip) & TPM_STS_COMMAND_READY)) {
> +		if (time_after(jiffies, stop)) {
> +			rc = -ETIMEDOUT;
> +			goto out_err;
> +		}
> +
> +		cr50_i2c_tis_ready(chip);
> +	}
> +
> +	while (len > 0) {
> +		u8 mask = TPM_STS_VALID;
> +
> +		/* Wait for data if this is not the first chunk */
> +		if (sent > 0)
> +			mask |= TPM_STS_DATA_EXPECT;
> +
> +		/* Read burst count and check status */
> +		rc = cr50_i2c_wait_burststs(chip, mask, &burstcnt, &status);
> +		if (rc < 0)
> +			goto out_err;
> +
> +		/*
> +		 * Use burstcnt - 1 to account for the address byte
> +		 * that is inserted by cr50_i2c_write()
> +		 */
> +		limit = min_t(size_t, burstcnt - 1, len);
> +		rc = cr50_i2c_write(chip, TPM_I2C_DATA_FIFO(priv->locality),
> +				    &buf[sent], limit);
> +		if (rc < 0) {
> +			dev_err(&chip->dev, "Write failed\n");
> +			goto out_err;
> +		}
> +
> +		sent += limit;
> +		len -= limit;
> +	}
> +
> +	/* Ensure TPM is not expecting more data */
> +	rc = cr50_i2c_wait_burststs(chip, TPM_STS_VALID, &burstcnt, &status);
> +	if (rc < 0)
> +		goto out_err;
> +	if (status & TPM_STS_DATA_EXPECT) {
> +		dev_err(&chip->dev, "Data still expected\n");
> +		rc = -EIO;
> +		goto out_err;
> +	}
> +
> +	/* Start the TPM command */
> +	rc = cr50_i2c_write(chip, TPM_I2C_STS(priv->locality), tpm_go,
> +			    sizeof(tpm_go));
> +	if (rc < 0) {
> +		dev_err(&chip->dev, "Start command failed\n");
> +		goto out_err;
> +	}
> +	return 0;
> +
> +out_err:
> +	/* Abort current transaction if still pending */
> +	if (cr50_i2c_tis_status(chip) & TPM_STS_COMMAND_READY)
> +		cr50_i2c_tis_ready(chip);
> +
> +	release_locality(chip, 0);
> +	return rc;
> +}
> +
> +/*
> + * cr50_i2c_req_canceled - callback to notify a request cancel
> + *
> + * @chip: TPM chip information
> + * @status: status given by the cancel callback
> + *
> + * Return if command is ready or not
> + */
> +static bool cr50_i2c_req_canceled(struct tpm_chip *chip, u8 status)
> +{
> +	return (status == TPM_STS_COMMAND_READY);
> +}
> +
> +static const struct tpm_class_ops cr50_i2c = {
> +	.flags = TPM_OPS_AUTO_STARTUP,
> +	.status = &cr50_i2c_tis_status,
> +	.recv = &cr50_i2c_tis_recv,
> +	.send = &cr50_i2c_tis_send,
> +	.cancel = &cr50_i2c_tis_ready,
> +	.req_complete_mask = TPM_STS_DATA_AVAIL | TPM_STS_VALID,
> +	.req_complete_val = TPM_STS_DATA_AVAIL | TPM_STS_VALID,
> +	.req_canceled = &cr50_i2c_req_canceled,
> +};
> +
> +static const struct i2c_device_id cr50_i2c_table[] = {
> +	{"cr50_i2c", 0},
> +	{}
> +};
> +MODULE_DEVICE_TABLE(i2c, cr50_i2c_table);
> +
> +#ifdef CONFIG_ACPI
> +static const struct acpi_device_id cr50_i2c_acpi_id[] = {
> +	{ "GOOG0005", 0 },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(acpi, cr50_i2c_acpi_id);
> +#endif
> +
> +#ifdef CONFIG_OF
> +static const struct of_device_id of_cr50_i2c_match[] = {
> +	{ .compatible = "google,cr50", },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, of_cr50_i2c_match);
> +#endif
> +
> +/*
> + * cr50_i2c_probe - driver prbe function
> + *
> + * @client: i2x client information
> + * @id: i2c device id
> + *
> + * Returns negative number for error, 0 for success.
> + */
> +static int cr50_i2c_probe(struct i2c_client *client,
> +			  const struct i2c_device_id *id)
> +{
> +	struct device *dev = &client->dev;
> +	struct tpm_chip *chip;
> +	struct priv_data *priv;
> +	u8 buf[4];
> +	u32 vendor;
> +	int rc;
> +
> +	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
> +		return -ENODEV;
> +
> +	chip = tpmm_chip_alloc(dev, &cr50_i2c);
> +	if (IS_ERR(chip))
> +		return PTR_ERR(chip);
> +
> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	/* cr50 is a TPM 2.0 chip */
> +	chip->flags |= TPM_CHIP_FLAG_TPM2;
> +	chip->flags |= TPM_CHIP_FLAG_FIRMWARE_POWER_MANAGED;
> +
> +	/* Default timeouts */
> +	chip->timeout_a = msecs_to_jiffies(TIS_SHORT_TIMEOUT);
> +	chip->timeout_b = msecs_to_jiffies(TIS_LONG_TIMEOUT);
> +	chip->timeout_c = msecs_to_jiffies(TIS_SHORT_TIMEOUT);
> +	chip->timeout_d = msecs_to_jiffies(TIS_SHORT_TIMEOUT);
> +
> +	dev_set_drvdata(&chip->dev, priv);
> +	init_completion(&priv->tpm_ready);
> +
> +	if (client->irq > 0) {
> +		rc = devm_request_irq(dev, client->irq, cr50_i2c_int_handler,
> +				      IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
> +				      dev->driver->name, chip);
> +		if (rc < 0) {
> +			dev_err(dev, "Failed to probe IRQ %d\n", client->irq);
> +			return rc;
> +		}
> +
> +		disable_irq(client->irq);
> +		priv->irq = client->irq;
> +	} else {
> +		dev_warn(dev, "No IRQ, will use %ums delay for TPM ready\n",
> +			 CR50_TIMEOUT_NOIRQ_MS);
> +	}
> +
> +	rc = request_locality(chip);
> +	if (rc < 0) {
> +		dev_err(dev, "Could not request locality\n");
> +		return rc;
> +	}
> +
> +	/* Read four bytes from DID_VID register */
> +	rc = cr50_i2c_read(chip, TPM_I2C_DID_VID(0), buf, sizeof(buf));
> +	if (rc < 0) {
> +		dev_err(dev, "Could not read vendor id\n");
> +		release_locality(chip, 1);
> +		return rc;
> +	}
> +
> +	vendor = le32_to_cpup((__le32 *)buf);
> +	if (vendor != CR50_I2C_DID_VID) {
> +		dev_err(dev, "Vendor ID did not match! ID was %08x\n", vendor);
> +		release_locality(chip, 1);
> +		return -ENODEV;
> +	}
> +
> +	dev_info(dev, "cr50 TPM 2.0 (i2c 0x%02x irq %d id 0x%x)\n",
> +		 client->addr, client->irq, vendor >> 16);
> +
> +	return tpm_chip_register(chip);
> +}
> +
> +/*
> + * cr50_i2c_probe - driver prbe function
> + *
> + * @client: i2x client information
> + *
> + * Returns 0
> + */
> +static int cr50_i2c_remove(struct i2c_client *client)
> +{
> +	struct tpm_chip *chip = i2c_get_clientdata(client);
> +
> +	tpm_chip_unregister(chip);
> +	release_locality(chip, 1);
> +
> +	return 0;
> +}
> +
> +static SIMPLE_DEV_PM_OPS(cr50_i2c_pm, tpm_pm_suspend, tpm_pm_resume);
> +
> +static struct i2c_driver cr50_i2c_driver = {
> +	.id_table = cr50_i2c_table,
> +	.probe = cr50_i2c_probe,
> +	.remove = cr50_i2c_remove,
> +	.driver = {
> +		.name = "cr50_i2c",
> +		.pm = &cr50_i2c_pm,
> +		.acpi_match_table = ACPI_PTR(cr50_i2c_acpi_id),
> +		.of_match_table = of_match_ptr(of_cr50_i2c_match),
> +	},
> +};
> +
> +module_i2c_driver(cr50_i2c_driver);
> +
> +MODULE_DESCRIPTION("cr50 TPM I2C Driver");
> +MODULE_LICENSE("GPL");
>

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