[PATCH] drivers: tee: i2c trampoline driver

[Jorge Ramirez-Ortiz, Foundries <jorge@foundries.io>]

On 23/12/20, Jens Wiklander wrote:
> Hi Jorge,

hey

> 
> On Mon, Dec 21, 2020 at 07:15:40PM +0100, Jorge Ramirez-Ortiz wrote:
> > This commit gives the secure world access to the I2C bus so it can
> > communicate with I2C slaves (tipically those would be secure elements
> > like the NXP SE050).
> > 
> > Tested on imx8mmevk.
> > 
> > Signed-off-by: Jorge Ramirez-Ortiz <jorge@foundries.io>
> > ---
> >  drivers/tee/optee/Makefile               |  1 +
> >  drivers/tee/optee/i2c.c                  | 88 ++++++++++++++++++++++++
> >  drivers/tee/optee/optee_msg.h            | 22 ++++++
> >  drivers/tee/optee/optee_msg_supplicant.h |  5 ++
> >  drivers/tee/optee/optee_private.h        | 12 ++++
> >  drivers/tee/optee/supplicant.c           |  3 +
> >  6 files changed, 131 insertions(+)
> >  create mode 100644 drivers/tee/optee/i2c.c
> > 
> > diff --git a/drivers/tee/optee/Makefile b/drivers/tee/optee/Makefile
> > index 928d3f8002..068c6e7aa1 100644
> > --- a/drivers/tee/optee/Makefile
> > +++ b/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
> > diff --git a/drivers/tee/optee/i2c.c b/drivers/tee/optee/i2c.c
> > new file mode 100644
> > index 0000000000..2ebbf1ff7c
> > --- /dev/null
> > +++ b/drivers/tee/optee/i2c.c
> > @@ -0,0 +1,88 @@
> > +// 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 struct {
> > +	struct udevice *dev;
> > +	int chip;
> > +	int bus;
> > +} xfer;
> > +
> > +void optee_suppl_cmd_i2c_transfer(struct udevice *dev,
> > +				  struct optee_msg_arg *arg)
> > +{
> > +	const uint64_t attr[] = {
> A u8 instead of uint64_t would give the same result.

ok

> 
> > +		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 = NULL;
> > +	struct tee_shm *shm = NULL;
> > +	uint8_t *buf = NULL;
> > +	size_t len = 0;
> > +	int chip = -1;
> > +	int bus = -1;
> > +	int ret = -1;
> > +
> > +	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]) {
> > +		arg->ret = TEE_ERROR_BAD_PARAMETERS;
> > +		return;
> > +	}
> > +
> > +	len = arg->params[2].u.tmem.size;
> > +	shm = (struct tee_shm *)(unsigned long)arg->params[2].u.tmem.shm_ref;
> Please replace tmem with rmem. The OPTEE_MSG_ATTR_TYPE_RMEM_INOUT above
> indicates that we're dealing with a struct optee_msg_param_rmem.

sure, thanks!

> 
> > +	buf = shm->addr;
> > +	if (!buf || !len)
> > +		goto bad;
> > +
> > +	bus = (int)arg->params[0].u.value.b;
> > +	chip = (int)arg->params[0].u.value.c;
> > +
> > +	if (!xfer.dev || xfer.chip != chip || xfer.bus != bus) {
> > +		if (i2c_get_chip_for_busnum(bus, chip, 0, &chip_dev))
> > +			goto bad;
> > +
> > +		xfer.dev = chip_dev;
> > +		xfer.chip = chip;
> > +		xfer.bus = bus;
> Is this caching safe? No risk of using stale data?

um no I dont think so - I can't think of a scenario that could cause
that error, but maybe someone else can comment?

> 
> Thanks,
> Jens
> 
> > +	}
> > +
> > +	if (arg->params[1].u.value.a & OPTEE_MSG_RPC_CMD_I2C_FLAGS_TEN_BIT)
> > +		if (i2c_set_chip_flags(xfer.dev, DM_I2C_CHIP_10BIT))
> > +			goto bad;
> > +
> > +	switch (arg->params[0].u.value.a) {
> > +	case OPTEE_MSG_RPC_CMD_I2C_TRANSFER_RD:
> > +		ret = dm_i2c_read(xfer.dev, 0, buf, len);
> > +		break;
> > +	case OPTEE_MSG_RPC_CMD_I2C_TRANSFER_WR:
> > +		ret = dm_i2c_write(xfer.dev, 0, buf, len);
> > +		break;
> > +	default:
> > +		goto bad;
> > +	}
> > +
> > +	if (ret) {
> > +		arg->ret = TEE_ERROR_COMMUNICATION;
> > +	} else {
> > +		arg->params[3].u.value.a = len;
> > +		arg->ret = TEE_SUCCESS;
> > +	}
> > +
> > +	return;
> > +bad:
> > +	arg->ret = TEE_ERROR_BAD_PARAMETERS;
> > +}
> > diff --git a/drivers/tee/optee/optee_msg.h b/drivers/tee/optee/optee_msg.h
> > index 24c60960fc..7cedb59a82 100644
> > --- a/drivers/tee/optee/optee_msg.h
> > +++ b/drivers/tee/optee/optee_msg.h
> > @@ -422,4 +422,26 @@ 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]  param[1].u.value.b		i2c retry (optional)
> > + *
> > + * [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 */
> > diff --git a/drivers/tee/optee/optee_msg_supplicant.h b/drivers/tee/optee/optee_msg_supplicant.h
> > index a0fb8063c8..963cfd4782 100644
> > --- a/drivers/tee/optee/optee_msg_supplicant.h
> > +++ b/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
> >   */
> > diff --git a/drivers/tee/optee/optee_private.h b/drivers/tee/optee/optee_private.h
> > index 9442d1c176..d7ab1f593f 100644
> > --- a/drivers/tee/optee/optee_private.h
> > +++ b/drivers/tee/optee/optee_private.h
> > @@ -60,6 +60,18 @@ static inline void optee_suppl_rpmb_release(struct udevice *dev)
> >  }
> >  #endif
> >  
> > +#ifdef CONFIG_DM_I2C
> > +void optee_suppl_cmd_i2c_transfer(struct udevice *dev,
> > +				  struct optee_msg_arg *arg);
> > +#else

this function below should be made static btw (issue was flagged
internally during testing by a team member). Perhaps the same should
be done for RPMB?

> > +void optee_suppl_cmd_i2c_transfer(struct udevice *dev,
> > +				  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 */
> > diff --git a/drivers/tee/optee/supplicant.c b/drivers/tee/optee/supplicant.c
> > index ae042b9a20..f7738983cd 100644
> > --- a/drivers/tee/optee/supplicant.c
> > +++ b/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(dev, arg);
> > +		break;
> >  	default:
> >  		arg->ret = TEE_ERROR_NOT_IMPLEMENTED;
> >  	}
> > -- 
> > 2.17.1
> >