Message-ID: <20160809102031.GC13566@intel.com>
Date:	Tue, 9 Aug 2016 13:20:31 +0300
From:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:	Andrey Pronin <apronin@...omium.org>
Cc:	Peter Huewe <peterhuewe@....de>,
	Marcel Selhorst <tpmdd@...horst.net>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	Christophe Ricard <christophe.ricard@...il.com>,
	dtor@...omium.org, smbarber@...omium.org, dianders@...omium.org
Subject: Re: [PATCH v4 2/2] tpm: add driver for cr50 on SPI

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@...omium.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
> 

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