linux-kernel - Re: [PATCH v2] drivers: optee: allow op-tee to access devices on the i2c bus

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Message-ID: <20200607173814.GA30457@trex>
Date:   Sun, 7 Jun 2020 19:38:14 +0200
From:   "Jorge Ramirez-Ortiz, Foundries" <jorge@...ndries.io>
To:     Jorge Ramirez-Ortiz <jorge@...ndries.io>
Cc:     jens.wiklander@...aro.org, tee-dev@...ts.linaro.org,
        linux-kernel@...r.kernel.org, ricardo@...ndries.io,
        mike@...ndries.io
Subject: Re: [PATCH v2] drivers: optee: allow op-tee to access devices on the
 i2c bus

On 01/06/20, Jorge Ramirez-Ortiz wrote:
> 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.


any comments please?


> 
> Signed-off-by: Jorge Ramirez-Ortiz <jorge@...ndries.io>
> ---
>  drivers/tee/optee/optee_msg.h | 18 +++++++++++
>  drivers/tee/optee/rpc.c       | 57 +++++++++++++++++++++++++++++++++++
>  2 files changed, 75 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..21d452805c6f 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 +49,59 @@ 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:
> +		i2c_put_adapter(client.adapter);
> +		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 +436,9 @@ 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
>