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

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Date:   Wed, 23 Sep 2020 14:13:56 +0200
From:   Jens Wiklander <jens.wiklander@...aro.org>
To:     "Jorge Ramirez-Ortiz, Foundries" <jorge@...ndries.io>
Cc:     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 Wed, Sep 23, 2020 at 01:26:31PM +0200, Jorge Ramirez-Ortiz, Foundries wrote:
> On 23/09/20, Jorge Ramirez-Ortiz, Foundries wrote:
> > 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)
> >
> 
> correction (of course)
>   - i2cdev_read --> i2c_master_recv
>   - i2cdev->write -->i2c_master_send
> > 
> > and now the retry count setup on the adaptor with this commit.
> > 
> >  - i2cdev_ioctl I2C_RETRIES

I don't understand. Do you mean that client.adapter->retries doesn't
need to be protected from concurrent updates? Or is it already protected
by some other mechanism?

Cheers,
Jens