linux-kernel - Re: [PATCH] drivers: optee: i2c: add bus retry configuration

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Message-ID: <20200923111813.GA30271@trex>
Date:   Wed, 23 Sep 2020 13:18:13 +0200
From:   "Jorge Ramirez-Ortiz, Foundries" <jorge@...ndries.io>
To:     Jens Wiklander <jens.wiklander@...aro.org>
Cc:     Jorge Ramirez-Ortiz <jorge@...ndries.io>, sumit.garg@...aro.org,
        ricardo@...ndries.io, mike@...ndries.io, tee-dev@...ts.linaro.org,
        linux-kernel@...r.kernel.org, op-tee@...ts.trustedfirmware.org
Subject: Re: [PATCH] drivers: optee: i2c: add bus retry configuration

On 22/09/20, Jens Wiklander wrote:
> On Wed, Sep 16, 2020 at 05:27:32PM +0200, Jorge Ramirez-Ortiz wrote:
> > Allow OP-TEE to specify the number of retries in the adaptor.
> > 
> > Signed-off-by: Jorge Ramirez-Ortiz <jorge@...ndries.io>
> > ---
> >  drivers/tee/optee/rpc.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/drivers/tee/optee/rpc.c b/drivers/tee/optee/rpc.c
> > index 1e3614e4798f..2d46a9ecb1de 100644
> > --- a/drivers/tee/optee/rpc.c
> > +++ b/drivers/tee/optee/rpc.c
> > @@ -58,6 +58,7 @@ static void handle_rpc_func_cmd_i2c_transfer(struct tee_context *ctx,
> >  	struct tee_param *params;
> >  	size_t i;
> >  	int ret = -EOPNOTSUPP;
> > +	int retries = 0;
> >  	u8 attr[] = {
> >  		TEE_IOCTL_PARAM_ATTR_TYPE_VALUE_INPUT,
> >  		TEE_IOCTL_PARAM_ATTR_TYPE_VALUE_INPUT,
> > @@ -102,12 +103,17 @@ static void handle_rpc_func_cmd_i2c_transfer(struct tee_context *ctx,
> >  	client.addr = params[0].u.value.c;
> >  	snprintf(client.name, I2C_NAME_SIZE, "i2c%d", client.adapter->nr);
> >  
> > +	/* cache the current value */
> > +	retries = client.adapter->retries;
> > +
> >  	switch (params[0].u.value.a) {
> >  	case OPTEE_MSG_RPC_CMD_I2C_TRANSFER_RD:
> > +		client.adapter->retries = params[1].u.value.b;
> Do we need to take any locks befor this?

no I dont think so: there is no need for bus locks when requesting a
transfer via i2c_master_recv/send; the lock for the bus segment gets
taken later on, when the actual transfer hppens ( __i2c_transfer())

the functionality implemented in this function pretty much mimicks
what is done in the normal world via /dev/i2c-X
(drivers/i2c/i2c_dev.c)

 - i2cdev_read --> i2c_master_send
 - i2cdev->write -->i2c_master_recv

and now the retry count setup on the adaptor with this commit.

 - i2cdev_ioctl I2C_RETRIES

> 
> Cheers,
> Jens
> 
> >  		ret = i2c_master_recv(&client, params[2].u.memref.shm->kaddr,
> >  				      params[2].u.memref.size);
> >  		break;
> >  	case OPTEE_MSG_RPC_CMD_I2C_TRANSFER_WR:
> > +		client.adapter->retries = params[1].u.value.b;
> >  		ret = i2c_master_send(&client, params[2].u.memref.shm->kaddr,
> >  				      params[2].u.memref.size);
> >  		break;
> > @@ -126,6 +132,7 @@ static void handle_rpc_func_cmd_i2c_transfer(struct tee_context *ctx,
> >  			arg->ret = TEEC_SUCCESS;
> >  	}
> >  
> > +	client.adapter->retries = retries;
> >  	i2c_put_adapter(client.adapter);
> >  	kfree(params);
> >  	return;
> > -- 
> > 2.17.1
> >