text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   * Copyright (C) 2015 Infineon Technologies AG
   * Copyright (C) 2016 STMicroelectronics SAS
   *
   * Authors:
   * Peter Huewe <peter.huewe@infineon.com>
   * Christophe Ricard <christophe-h.ricard@st.com>
   *
   * Maintained by: <tpmdd-devel@lists.sourceforge.net>
   *
   * Device driver for TCG/TCPA TPM (trusted platform module).
   * Specifications at www.trustedcomputinggroup.org
   *
   * This device driver implements the TPM interface as defined in
   * the TCG TPM Interface Spec version 1.3, revision 27 via _raw/native
   * SPI access_.
   *
   * It is based on the original tpm_tis device driver from Leendert van
   * Dorn and Kyleen Hall and Jarko Sakkinnen.
   */
  
  #include <linux/acpi.h>
  #include <linux/completion.h>
  #include <linux/init.h>
  #include <linux/interrupt.h>
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/slab.h>
  
  #include <linux/of_device.h>
  #include <linux/spi/spi.h>
  #include <linux/tpm.h>
  
  #include "tpm.h"
  #include "tpm_tis_core.h"
  #include "tpm_tis_spi.h"
  
  #define MAX_SPI_FRAMESIZE 64
  
  /*
   * TCG SPI flow control is documented in section 6.4 of the spec[1]. In short,
   * keep trying to read from the device until MISO goes high indicating the
   * wait state has ended.
   *
   * [1] https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
   */
  static int tpm_tis_spi_flow_control(struct tpm_tis_spi_phy *phy,
  				    struct spi_transfer *spi_xfer)
  {
  	struct spi_message m;
  	int ret, i;
  
  	if ((phy->iobuf[3] & 0x01) == 0) {
  		// handle SPI wait states
  		phy->iobuf[0] = 0;
  
  		for (i = 0; i < TPM_RETRY; i++) {
  			spi_xfer->len = 1;
  			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 (phy->iobuf[0] & 0x01)
  				break;
  		}
  
  		if (i == TPM_RETRY)
  			return -ETIMEDOUT;
  	}
  
  	return 0;
  }
  
  int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
  			 u8 *in, const u8 *out)
  {
  	struct tpm_tis_spi_phy *phy = to_tpm_tis_spi_phy(data);
  	int ret = 0;
  	struct spi_message m;
  	struct spi_transfer spi_xfer;
  	u8 transfer_len;
  
  	spi_bus_lock(phy->spi_device->master);
  
  	while (len) {
  		transfer_len = min_t(u16, len, MAX_SPI_FRAMESIZE);
  
  		phy->iobuf[0] = (in ? 0x80 : 0) | (transfer_len - 1);
  		phy->iobuf[1] = 0xd4;
  		phy->iobuf[2] = addr >> 8;
  		phy->iobuf[3] = addr;
  
  		memset(&spi_xfer, 0, sizeof(spi_xfer));
  		spi_xfer.tx_buf = phy->iobuf;
  		spi_xfer.rx_buf = phy->iobuf;
  		spi_xfer.len = 4;
  		spi_xfer.cs_change = 1;
  
  		spi_message_init(&m);
  		spi_message_add_tail(&spi_xfer, &m);
  		ret = spi_sync_locked(phy->spi_device, &m);
  		if (ret < 0)
  			goto exit;
  
  		ret = phy->flow_control(phy, &spi_xfer);
  		if (ret < 0)
  			goto exit;
  
  		spi_xfer.cs_change = 0;
  		spi_xfer.len = transfer_len;
  		spi_xfer.delay_usecs = 5;
  
  		if (in) {
  			spi_xfer.tx_buf = NULL;
  		} else if (out) {
  			spi_xfer.rx_buf = NULL;
  			memcpy(phy->iobuf, out, transfer_len);
  			out += transfer_len;
  		}
  
  		spi_message_init(&m);
  		spi_message_add_tail(&spi_xfer, &m);
  		reinit_completion(&phy->ready);
  		ret = spi_sync_locked(phy->spi_device, &m);
  		if (ret < 0)
  			goto exit;
  
  		if (in) {
  			memcpy(in, phy->iobuf, transfer_len);
  			in += transfer_len;
  		}
  
  		len -= transfer_len;
  	}
  
  exit:
  	spi_bus_unlock(phy->spi_device->master);
  	return ret;
  }
  
  static int tpm_tis_spi_read_bytes(struct tpm_tis_data *data, u32 addr,
  				  u16 len, u8 *result)
  {
  	return tpm_tis_spi_transfer(data, addr, len, result, NULL);
  }
  
  static int tpm_tis_spi_write_bytes(struct tpm_tis_data *data, u32 addr,
  				   u16 len, const u8 *value)
  {
  	return tpm_tis_spi_transfer(data, addr, len, NULL, value);
  }
  
  int tpm_tis_spi_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_spi_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_spi_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;
  }
  
  int tpm_tis_spi_init(struct spi_device *spi, struct tpm_tis_spi_phy *phy,
  		     int irq, const struct tpm_tis_phy_ops *phy_ops)
  {
  	phy->iobuf = devm_kmalloc(&spi->dev, MAX_SPI_FRAMESIZE, GFP_KERNEL);
  	if (!phy->iobuf)
  		return -ENOMEM;
  
  	phy->spi_device = spi;
  
  	return tpm_tis_core_init(&spi->dev, &phy->priv, irq, phy_ops, NULL);
  }
  
  static const struct tpm_tis_phy_ops tpm_spi_phy_ops = {
  	.read_bytes = tpm_tis_spi_read_bytes,
  	.write_bytes = tpm_tis_spi_write_bytes,
  	.read16 = tpm_tis_spi_read16,
  	.read32 = tpm_tis_spi_read32,
  	.write32 = tpm_tis_spi_write32,
  };
  
  static int tpm_tis_spi_probe(struct spi_device *dev)
  {
  	struct tpm_tis_spi_phy *phy;
  	int irq;
  
  	phy = devm_kzalloc(&dev->dev, sizeof(struct tpm_tis_spi_phy),
  			   GFP_KERNEL);
  	if (!phy)
  		return -ENOMEM;
  
  	phy->flow_control = tpm_tis_spi_flow_control;
  
  	/* If the SPI device has an IRQ then use that */
  	if (dev->irq > 0)
  		irq = dev->irq;
  	else
  		irq = -1;
  
  	init_completion(&phy->ready);
  	return tpm_tis_spi_init(dev, phy, irq, &tpm_spi_phy_ops);
  }
  
  typedef int (*tpm_tis_spi_probe_func)(struct spi_device *);
  
  static int tpm_tis_spi_driver_probe(struct spi_device *spi)
  {
  	const struct spi_device_id *spi_dev_id = spi_get_device_id(spi);
  	tpm_tis_spi_probe_func probe_func;
  
  	probe_func = of_device_get_match_data(&spi->dev);
  	if (!probe_func && spi_dev_id)
  		probe_func = (tpm_tis_spi_probe_func)spi_dev_id->driver_data;
  	if (!probe_func)
  		return -ENODEV;
  
  	return probe_func(spi);
  }
  
  static SIMPLE_DEV_PM_OPS(tpm_tis_pm, tpm_pm_suspend, tpm_tis_spi_resume);
  
  static int tpm_tis_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 tpm_tis_spi_id[] = {
  	{ "tpm_tis_spi", (unsigned long)tpm_tis_spi_probe },
  	{ "cr50", (unsigned long)cr50_spi_probe },
  	{}
  };
  MODULE_DEVICE_TABLE(spi, tpm_tis_spi_id);
  
  static const struct of_device_id of_tis_spi_match[] = {
  	{ .compatible = "st,st33htpm-spi", .data = tpm_tis_spi_probe },
  	{ .compatible = "infineon,slb9670", .data = tpm_tis_spi_probe },
  	{ .compatible = "tcg,tpm_tis-spi", .data = tpm_tis_spi_probe },
  	{ .compatible = "google,cr50", .data = cr50_spi_probe },
  	{}
  };
  MODULE_DEVICE_TABLE(of, of_tis_spi_match);
  
  static const struct acpi_device_id acpi_tis_spi_match[] = {
  	{"SMO0768", 0},
  	{}
  };
  MODULE_DEVICE_TABLE(acpi, acpi_tis_spi_match);
  
  static struct spi_driver tpm_tis_spi_driver = {
  	.driver = {
  		.name = "tpm_tis_spi",
  		.pm = &tpm_tis_pm,
  		.of_match_table = of_match_ptr(of_tis_spi_match),
  		.acpi_match_table = ACPI_PTR(acpi_tis_spi_match),
  	},
  	.probe = tpm_tis_spi_driver_probe,
  	.remove = tpm_tis_spi_remove,
  	.id_table = tpm_tis_spi_id,
  };
  module_spi_driver(tpm_tis_spi_driver);
  
  MODULE_DESCRIPTION("TPM Driver for native SPI access");
  MODULE_LICENSE("GPL");
  