linux-kernel - [PATCH] drivers: optee: allow op-tee to access devices on the i2c bus

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Message-Id: <20200531203809.3397-1-jorge@foundries.io>
Date:   Sun, 31 May 2020 22:38:09 +0200
From:   Jorge Ramirez-Ortiz <jorge@...ndries.io>
To:     jorge@...ndries.io, jens.wiklander@...aro.org
Cc:     tee-dev@...ts.linaro.org, linux-kernel@...r.kernel.org,
        ricardo@...ndries.io, mike@...ndries.io
Subject: [PATCH] drivers: optee: allow op-tee to access devices on the i2c bus

Some secure elements like NXP's SE050 sit on I2C buses. For OP-TEE to
control this type of cryptographic devices it needs coordinated access
to the bus, so collisions and RUNTIME_PM dont get in the way.

This trampoline driver allow OP-TEE to access them.

Signed-off-by: Jorge Ramirez-Ortiz <jorge@...ndries.io>
---
 drivers/tee/optee/optee_msg.h | 18 +++++++++++
 drivers/tee/optee/rpc.c       | 56 +++++++++++++++++++++++++++++++++++
 2 files changed, 74 insertions(+)

diff --git a/drivers/tee/optee/optee_msg.h b/drivers/tee/optee/optee_msg.h
index 795bc19ae17a..b6cc964fdeea 100644
--- a/drivers/tee/optee/optee_msg.h
+++ b/drivers/tee/optee/optee_msg.h
@@ -419,4 +419,22 @@ 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
+ *
+ * [io]  param[1].u.tmem.buf_ptr	physical address
+ * [io]  param[1].u.tmem.size		transfer size in bytes
+ * [io]  param[1].u.tmem.shm_ref	shared memory reference
+ *
+ * [out]  param[0].u.value.a		bytes transferred
+ *
+ */
+#define OPTEE_MSG_RPC_CMD_I2C_TRANSFER 8
+#define OPTEE_MSG_RPC_CMD_I2C_TRANSFER_RD 0
+#define OPTEE_MSG_RPC_CMD_I2C_TRANSFER_WR 1
+
 #endif /* _OPTEE_MSG_H */
diff --git a/drivers/tee/optee/rpc.c b/drivers/tee/optee/rpc.c
index b4ade54d1f28..6c8457ac2524 100644
--- a/drivers/tee/optee/rpc.c
+++ b/drivers/tee/optee/rpc.c
@@ -9,6 +9,7 @@
 #include <linux/device.h>
 #include <linux/slab.h>
 #include <linux/tee_drv.h>
+#include <linux/i2c.h>
 #include "optee_private.h"
 #include "optee_smc.h"
 
@@ -48,6 +49,58 @@ static void handle_rpc_func_cmd_get_time(struct optee_msg_arg *arg)
 bad:
 	arg->ret = TEEC_ERROR_BAD_PARAMETERS;
 }
+static void handle_rpc_func_cmd_i2c_transfer(struct tee_context *ctx,
+					     struct optee_msg_arg *arg)
+{
+	struct i2c_client client;
+	struct tee_shm *shm;
+	int i, ret;
+	char *buf;
+	uint32_t attr[] = {
+		OPTEE_MSG_ATTR_TYPE_VALUE_INPUT,
+		OPTEE_MSG_ATTR_TYPE_TMEM_INOUT,
+		OPTEE_MSG_ATTR_TYPE_VALUE_OUTPUT,
+	};
+
+	if (arg->num_params != ARRAY_SIZE(attr))
+		goto bad;
+
+	for (i = 0; i < ARRAY_SIZE(attr); i++)
+		if ((arg->params[i].attr & OPTEE_MSG_ATTR_TYPE_MASK) != attr[i])
+			goto bad;
+
+	shm = (struct tee_shm *)(unsigned long)arg->params[1].u.tmem.shm_ref;
+	buf = (char *)shm->kaddr;
+
+	client.addr = arg->params[0].u.value.c;
+	client.adapter = i2c_get_adapter(arg->params[0].u.value.b);
+	if (!client.adapter)
+		goto bad;
+
+	snprintf(client.name, I2C_NAME_SIZE, "i2c%d", client.adapter->nr);
+
+	switch (arg->params[0].u.value.a) {
+	case OPTEE_MSG_RPC_CMD_I2C_TRANSFER_RD:
+		ret = i2c_master_recv(&client, buf, arg->params[1].u.tmem.size);
+		break;
+	case OPTEE_MSG_RPC_CMD_I2C_TRANSFER_WR:
+		ret = i2c_master_send(&client, buf, arg->params[1].u.tmem.size);
+		break;
+	default:
+		goto bad;
+	}
+
+	if (ret >= 0) {
+		arg->params[2].u.value.a = ret;
+		arg->ret = TEEC_SUCCESS;
+	} else
+		arg->ret = TEEC_ERROR_COMMUNICATION;
+
+	i2c_put_adapter(client.adapter);
+	return;
+bad:
+	arg->ret = TEEC_ERROR_BAD_PARAMETERS;
+}
 
 static struct wq_entry *wq_entry_get(struct optee_wait_queue *wq, u32 key)
 {
@@ -382,6 +435,9 @@ static void handle_rpc_func_cmd(struct tee_context *ctx, struct optee *optee,
 	case OPTEE_MSG_RPC_CMD_SHM_FREE:
 		handle_rpc_func_cmd_shm_free(ctx, arg);
 		break;
+	case OPTEE_MSG_RPC_CMD_I2C_TRANSFER:
+		handle_rpc_func_cmd_i2c_transfer(ctx, arg);
+		break;
 	default:
 		handle_rpc_supp_cmd(ctx, arg);
 	}
-- 
2.17.1