linux-kernel - Re: [PATCHv6] drivers: optee: allow op-tee to access devices on the i2c bus

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Message-ID: <20200728100849.GA2365@trex>
Date:   Tue, 28 Jul 2020 12:08:49 +0200
From:   "Jorge Ramirez-Ortiz, Foundries" <jorge@...ndries.io>
To:     Jorge Ramirez-Ortiz <jorge@...ndries.io>
Cc:     jens.wiklander@...aro.org, sumit.garg@...aro.org,
        ricardo@...ndries.io, mike@...ndries.io, tee-dev@...ts.linaro.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCHv6] drivers: optee: allow op-tee to access devices on the
 i2c bus

On 22/07/20, 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.
> Tested on imx8mm LPDDR4
> 
> Signed-off-by: Jorge Ramirez-Ortiz <jorge@...ndries.io>
> ---
>  v6: compile out if CONFIG_I2C not enabled
>  v5: alphabetic order of includes
>  v4: remove unnecessary extra line in optee_msg.h
>  v3: use from/to msg param to support all types of memory
>      modify OPTEE_MSG_RPC_CMD_I2C_TRANSFER message id
>      
>  drivers/tee/optee/optee_msg.h | 16 +++++++
>  drivers/tee/optee/rpc.c       | 88 +++++++++++++++++++++++++++++++++++
>  2 files changed, 104 insertions(+)
> 
> diff --git a/drivers/tee/optee/optee_msg.h b/drivers/tee/optee/optee_msg.h
> index 795bc19ae17a..14b580f55356 100644
> --- a/drivers/tee/optee/optee_msg.h
> +++ b/drivers/tee/optee/optee_msg.h
> @@ -419,4 +419,20 @@ 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/out] memref[1]			buffer to exchange the transfer data
> + *					with the secure world
> + *
> + * [out]  param[0].u.value.a		bytes transferred by the driver
> + */
> +#define OPTEE_MSG_RPC_CMD_I2C_TRANSFER 21
> +#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..5fd5c6c93896 100644
> --- a/drivers/tee/optee/rpc.c
> +++ b/drivers/tee/optee/rpc.c
> @@ -7,6 +7,7 @@
>  
>  #include <linux/delay.h>
>  #include <linux/device.h>
> +#include <linux/i2c.h>
>  #include <linux/slab.h>
>  #include <linux/tee_drv.h>
>  #include "optee_private.h"
> @@ -49,6 +50,90 @@ static void handle_rpc_func_cmd_get_time(struct optee_msg_arg *arg)
>  	arg->ret = TEEC_ERROR_BAD_PARAMETERS;
>  }
>  
> +#if IS_ENABLED(CONFIG_I2C)
> +static void handle_rpc_func_cmd_i2c_transfer(struct tee_context *ctx,
> +					     struct optee_msg_arg *arg)
> +{
> +	struct i2c_client client;
> +	struct tee_param *params;
> +	uint32_t type;
> +	int i, ret;
> +	size_t len;
> +	char *buf;
> +	uint32_t attr[] = {
> +		TEE_IOCTL_PARAM_ATTR_TYPE_VALUE_INPUT,
> +		TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_INOUT,
> +		TEE_IOCTL_PARAM_ATTR_TYPE_VALUE_OUTPUT,
> +	};
> +
> +	if (arg->num_params != ARRAY_SIZE(attr)) {
> +		arg->ret = TEEC_ERROR_BAD_PARAMETERS;
> +		return;
> +	}
> +
> +	params = kmalloc_array(arg->num_params, sizeof(struct tee_param),
> +			       GFP_KERNEL);
> +	if (!params) {
> +		arg->ret = TEEC_ERROR_OUT_OF_MEMORY;
> +		return;
> +	}
> +
> +	if (optee_from_msg_param(params, arg->num_params, arg->params))
> +		goto bad;
> +
> +	for (i = 0; i < arg->num_params; i++) {
> +		type = params[i].attr & TEE_IOCTL_PARAM_ATTR_TYPE_MASK;
> +		if (type != attr[i])
> +			goto bad;
> +	}
> +
> +	client.addr = params[0].u.value.c;
> +	client.adapter = i2c_get_adapter(params[0].u.value.b);
> +	if (!client.adapter)
> +		goto bad;
> +
> +	snprintf(client.name, I2C_NAME_SIZE, "i2c%d", client.adapter->nr);
> +
> +	buf = params[1].u.memref.shm->kaddr;
> +	len = params[1].u.memref.size;
> +
> +	switch (params[0].u.value.a) {
> +	case OPTEE_MSG_RPC_CMD_I2C_TRANSFER_RD:
> +		ret = i2c_master_recv(&client, buf, len);
> +		break;
> +	case OPTEE_MSG_RPC_CMD_I2C_TRANSFER_WR:
> +		ret = i2c_master_send(&client, buf, len);
> +		break;
> +	default:
> +		i2c_put_adapter(client.adapter);
> +		goto bad;
> +	}
> +
> +	if (ret >= 0) {
> +		params[2].u.value.a = ret;
> +		arg->ret = TEEC_SUCCESS;
> +	} else {
> +		arg->ret = TEEC_ERROR_COMMUNICATION;
> +	}
> +
> +	if (optee_to_msg_param(arg->params, arg->num_params, params))
> +		arg->ret = TEEC_ERROR_BAD_PARAMETERS;
> +
> +	i2c_put_adapter(client.adapter);
> +	kfree(params);
> +	return;
> +bad:
> +	kfree(params);
> +	arg->ret = TEEC_ERROR_BAD_PARAMETERS;
> +}
> +#else
> +static void handle_rpc_func_cmd_i2c_transfer(struct tee_context *ctx,
> +					     struct optee_msg_arg *arg)
> +{
> +	arg->ret = TEEC_ERROR_COMMUNICATION;
> +}
> +#endif
> +
>  static struct wq_entry *wq_entry_get(struct optee_wait_queue *wq, u32 key)
>  {
>  	struct wq_entry *w;
> @@ -382,6 +467,9 @@ 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);
>  	}

any comments to this feature?

TIA