drivers: tee: i2c trampoline driver

This commit gives the secure world access to the I2C bus so it can
communicate with I2C slaves (typically those would be secure elements
like the NXP SE050).

A similar service implementation has been merged in linux:
c05210ab ("drivers: optee: allow op-tee to access devices on the i2c
bus")

Signed-off-by: Jorge Ramirez-Ortiz <jorge@foundries.io>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Etienne Carriere <etienne.carriere@linaro.org>

drivers/tee/optee/Makefile

@@ -2,4 +2,5 @@
 
 obj-y += core.o
 obj-y += supplicant.o
+obj-$(CONFIG_DM_I2C) += i2c.o
 obj-$(CONFIG_SUPPORT_EMMC_RPMB) += rpmb.o

drivers/tee/optee/i2c.c

@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: BSD-2-Clause
+/*
+ * Copyright (c) 2020 Foundries.io Ltd
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <i2c.h>
+#include <tee.h>
+#include "optee_msg.h"
+#include "optee_private.h"
+
+static int check_xfer_flags(struct udevice *chip, uint tee_flags)
+{
+	uint flags;
+	int ret;
+
+	ret = i2c_get_chip_flags(chip, &flags);
+	if (ret)
+		return ret;
+
+	if (tee_flags & OPTEE_MSG_RPC_CMD_I2C_FLAGS_TEN_BIT) {
+		if (!(flags & DM_I2C_CHIP_10BIT))
+			return -EINVAL;
+	} else {
+		if (flags & DM_I2C_CHIP_10BIT)
+			return -EINVAL;
+	}
+
+	return 0;
+}
+
+void optee_suppl_cmd_i2c_transfer(struct optee_msg_arg *arg)
+{
+	const u8 attr[] = {
+		OPTEE_MSG_ATTR_TYPE_VALUE_INPUT,
+		OPTEE_MSG_ATTR_TYPE_VALUE_INPUT,
+		OPTEE_MSG_ATTR_TYPE_RMEM_INOUT,
+		OPTEE_MSG_ATTR_TYPE_VALUE_OUTPUT,
+	};
+	struct udevice *chip_dev;
+	struct tee_shm *shm;
+	u8 *buf;
+	int ret;
+
+	if (arg->num_params != ARRAY_SIZE(attr) ||
+	    arg->params[0].attr != attr[0] ||
+	    arg->params[1].attr != attr[1] ||
+	    arg->params[2].attr != attr[2] ||
+	    arg->params[3].attr != attr[3]) {
+		goto bad;
+	}
+
+	shm = (struct tee_shm *)(unsigned long)arg->params[2].u.rmem.shm_ref;
+	buf = shm->addr;
+	if (!buf)
+		goto bad;
+
+	if (i2c_get_chip_for_busnum((int)arg->params[0].u.value.b,
+				    (int)arg->params[0].u.value.c,
+				    0, &chip_dev))
+		goto bad;
+
+	if (check_xfer_flags(chip_dev, arg->params[1].u.value.a))
+		goto bad;
+
+	switch (arg->params[0].u.value.a) {
+	case OPTEE_MSG_RPC_CMD_I2C_TRANSFER_RD:
+		ret = dm_i2c_read(chip_dev, 0, buf,
+				  (size_t)arg->params[2].u.rmem.size);
+		break;
+	case OPTEE_MSG_RPC_CMD_I2C_TRANSFER_WR:
+		ret = dm_i2c_write(chip_dev, 0, buf,
+				   (size_t)arg->params[2].u.rmem.size);
+		break;
+	default:
+		goto bad;
+	}
+
+	if (ret) {
+		arg->ret = TEE_ERROR_COMMUNICATION;
+	} else {
+		arg->params[3].u.value.a = arg->params[2].u.rmem.size;
+		arg->ret = TEE_SUCCESS;
+	}
+
+	return;
+bad:
+	arg->ret = TEE_ERROR_BAD_PARAMETERS;
+}

drivers/tee/optee/optee_msg.h

@@ -422,4 +422,25 @@ struct optee_msg_arg {
  */
 #define OPTEE_MSG_RPC_CMD_SHM_FREE	7
 
+/*
+ * Access a device on an i2c bus
+ *
+ * [in]  param[0].u.value.a		mode: RD(0), WR(1)
+ * [in]  param[0].u.value.b		i2c adapter
+ * [in]  param[0].u.value.c		i2c chip
+ *
+ * [in]  param[1].u.value.a		i2c control flags
+ *
+ * [in/out] memref[2]			buffer to exchange the transfer data
+ *					with the secure world
+ *
+ * [out]  param[3].u.value.a		bytes transferred by the driver
+ */
+#define OPTEE_MSG_RPC_CMD_I2C_TRANSFER 21
+/* I2C master transfer modes */
+#define OPTEE_MSG_RPC_CMD_I2C_TRANSFER_RD 0
+#define OPTEE_MSG_RPC_CMD_I2C_TRANSFER_WR 1
+/* I2C master control flags */
+#define OPTEE_MSG_RPC_CMD_I2C_FLAGS_TEN_BIT  BIT(0)
+
 #endif /* _OPTEE_MSG_H */

drivers/tee/optee/optee_msg_supplicant.h

@@ -147,6 +147,11 @@
 #define OPTEE_MSG_RPC_CMD_SHM_ALLOC	6
 #define OPTEE_MSG_RPC_CMD_SHM_FREE	7
 
+/*
+ * I2C bus access
+ */
+#define OPTEE_MSG_RPC_CMD_I2C_TRANSFER 21
+
 /*
  * Was OPTEE_MSG_RPC_CMD_SQL_FS, which isn't supported any longer
  */

drivers/tee/optee/optee_private.h

@@ -60,6 +60,23 @@ static inline void optee_suppl_rpmb_release(struct udevice *dev)
 }
 #endif
 
+#ifdef CONFIG_DM_I2C
+/**
+ * optee_suppl_cmd_i2c_transfer() - route I2C requests to an I2C chip
+ * @arg:	OP-TEE message (layout specified in optee_msg.h) defining the
+ *		transfer mode (read/write), adapter, chip and control flags.
+ *
+ * Handles OP-TEE requests to transfer data to the I2C chip on the I2C adapter.
+ */
+void optee_suppl_cmd_i2c_transfer(struct optee_msg_arg *arg);
+#else
+static inline void optee_suppl_cmd_i2c_transfer(struct optee_msg_arg *arg)
+{
+	debug("OPTEE_MSG_RPC_CMD_I2C_TRANSFER not implemented\n");
+	arg->ret = TEE_ERROR_NOT_IMPLEMENTED;
+}
+#endif
+
 void *optee_alloc_and_init_page_list(void *buf, ulong len, u64 *phys_buf_ptr);
 
 #endif /* __OPTEE_PRIVATE_H */

drivers/tee/optee/supplicant.c

@@ -89,6 +89,9 @@ void optee_suppl_cmd(struct udevice *dev, struct tee_shm *shm_arg,
 	case OPTEE_MSG_RPC_CMD_RPMB:
 		optee_suppl_cmd_rpmb(dev, arg);
 		break;
+	case OPTEE_MSG_RPC_CMD_I2C_TRANSFER:
+		optee_suppl_cmd_i2c_transfer(arg);
+		break;
 	default:
 		arg->ret = TEE_ERROR_NOT_IMPLEMENTED;
 	}