tpm: Add a driver for Loongson TPM device

Loongson Security Engine supports random number generation, hash,
symmetric encryption and asymmetric encryption. Based on these
encryption functions, TPM2 have been implemented in the Loongson
Security Engine firmware. This driver is responsible for copying data
into the memory visible to the firmware and receiving data from the
firmware.

Co-developed-by: Yinggang Gu <guyinggang@loongson.cn>
Signed-off-by: Yinggang Gu <guyinggang@loongson.cn>
Signed-off-by: Qunqin Zhao <zhaoqunqin@loongson.cn>
Reviewed-by: Huacai Chen <chenhuacai@loongson.cn>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lore.kernel.org/r/20250705072045.1067-4-zhaoqunqin@loongson.cn
Signed-off-by: Lee Jones <lee@kernel.org>

drivers/char/tpm/Kconfig

@@ -189,6 +189,15 @@ config TCG_IBMVTPM
 	  will be accessible from within Linux.  To compile this driver
 	  as a module, choose M here; the module will be called tpm_ibmvtpm.
 
+config TCG_LOONGSON
+	tristate "Loongson TPM Interface"
+	depends on MFD_LOONGSON_SE
+	help
+	  If you want to make Loongson TPM support available, 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_loongson.
+
 config TCG_XEN
 	tristate "XEN TPM Interface"
 	depends on TCG_TPM && XEN

drivers/char/tpm/Makefile

@@ -46,3 +46,4 @@ obj-$(CONFIG_TCG_ARM_CRB_FFA) += tpm_crb_ffa.o
 obj-$(CONFIG_TCG_VTPM_PROXY) += tpm_vtpm_proxy.o
 obj-$(CONFIG_TCG_FTPM_TEE) += tpm_ftpm_tee.o
 obj-$(CONFIG_TCG_SVSM) += tpm_svsm.o
+obj-$(CONFIG_TCG_LOONGSON) += tpm_loongson.o

drivers/char/tpm/tpm_loongson.c

@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Loongson Technology Corporation Limited. */
+
+#include <linux/device.h>
+#include <linux/mfd/loongson-se.h>
+#include <linux/platform_device.h>
+#include <linux/wait.h>
+
+#include "tpm.h"
+
+struct tpm_loongson_cmd {
+	u32 cmd_id;
+	u32 data_off;
+	u32 data_len;
+	u32 pad[5];
+};
+
+static int tpm_loongson_recv(struct tpm_chip *chip, u8 *buf, size_t count)
+{
+	struct loongson_se_engine *tpm_engine = dev_get_drvdata(&chip->dev);
+	struct tpm_loongson_cmd *cmd_ret = tpm_engine->command_ret;
+
+	if (cmd_ret->data_len > count)
+		return -EIO;
+
+	memcpy(buf, tpm_engine->data_buffer, cmd_ret->data_len);
+
+	return cmd_ret->data_len;
+}
+
+static int tpm_loongson_send(struct tpm_chip *chip, u8 *buf, size_t count)
+{
+	struct loongson_se_engine *tpm_engine = dev_get_drvdata(&chip->dev);
+	struct tpm_loongson_cmd *cmd = tpm_engine->command;
+
+	if (count > tpm_engine->buffer_size)
+		return -E2BIG;
+
+	cmd->data_len = count;
+	memcpy(tpm_engine->data_buffer, buf, count);
+
+	return loongson_se_send_engine_cmd(tpm_engine);
+}
+
+static const struct tpm_class_ops tpm_loongson_ops = {
+	.flags = TPM_OPS_AUTO_STARTUP,
+	.recv = tpm_loongson_recv,
+	.send = tpm_loongson_send,
+};
+
+static int tpm_loongson_probe(struct platform_device *pdev)
+{
+	struct loongson_se_engine *tpm_engine;
+	struct device *dev = &pdev->dev;
+	struct tpm_loongson_cmd *cmd;
+	struct tpm_chip *chip;
+
+	tpm_engine = loongson_se_init_engine(dev->parent, SE_ENGINE_TPM);
+	if (!tpm_engine)
+		return -ENODEV;
+	cmd = tpm_engine->command;
+	cmd->cmd_id = SE_CMD_TPM;
+	cmd->data_off = tpm_engine->buffer_off;
+
+	chip = tpmm_chip_alloc(dev, &tpm_loongson_ops);
+	if (IS_ERR(chip))
+		return PTR_ERR(chip);
+	chip->flags = TPM_CHIP_FLAG_TPM2 | TPM_CHIP_FLAG_IRQ;
+	dev_set_drvdata(&chip->dev, tpm_engine);
+
+	return tpm_chip_register(chip);
+}
+
+static struct platform_driver tpm_loongson = {
+	.probe   = tpm_loongson_probe,
+	.driver  = {
+		.name  = "tpm_loongson",
+	},
+};
+module_platform_driver(tpm_loongson);
+
+MODULE_ALIAS("platform:tpm_loongson");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Loongson TPM driver");