Re: [PATCH v2 1/3] i3c: Drop support for I2C 10 bit addresing

[vitor <vitor.soares@synopsys.com>]

Hi,

On 27/02/19 12:10, Boris Brezillon wrote:
> Hi Vitor,
>
> On Wed, 27 Feb 2019 12:05:30 +0000
> vitor <vitor.soares@synopsys.com> wrote:
>
>> On 26/02/19 14:28, Przemyslaw Gaj wrote:
>>> This patch dropps support for I2C devices with 10 bit addressing. When I2C
>>> device with 10 bit address is defined in DT, I3C master registration fails.
>>>
>>> Signed-off-by: Przemyslaw Gaj <pgaj@cadence.com>
>>>
>>> ---
>>>
>>> Main changes between v1 and v2 are:
>>> - Add error message when registering I2C device with 10 bit address.
>>>
>>> ---
>>>  drivers/i3c/master.c | 9 +++++++++
>>>  1 file changed, 9 insertions(+)
>>>
>>> diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
>>> index 2dc628d..8c1e365 100644
>>> --- a/drivers/i3c/master.c
>>> +++ b/drivers/i3c/master.c
>>> @@ -1962,6 +1962,15 @@ of_i3c_master_add_i2c_boardinfo(struct i3c_master_controller *master,
>>>  	if (ret)
>>>  		return ret;
>>>  
>>> +	/* The I3C Specification does not clearly say I2C devices with 10-bit
>>> +	 * address are supported. These devices can't be passed properly through
>>> +	 * DEFSLVS command.
>>> +	 */  
>> IMO we just need to say 10-bit address not used or not supported in i3c.
> I'd like to keep a clear comment on why it cannot supported right now
> even though the spec is unclear about that. If the spec is updated to
> state that I2C devs using extended addresses are forbidden, then we'll
> update this comment accordingly.

I'm not sure if the terms aren't the same, but let's keep the comment.

>
>>> +	if (boardinfo->base.flags & I2C_CLIENT_TEN) {
>>> +		dev_err(&master->dev, "I2C device with 10 bit address not supported.");
>>> +		return -ENOTSUPP;
>>> +	}
>>> +
>>>  	/* LVR is encoded in reg[2]. */
>>>  	boardinfo->lvr = reg[2];
>>>    
>> Also need to change:
>>
>> #define I2C_MAX_ADDR            GENMASK(9, 0)
>> to
>> #define I2C_MAX_ADDR            GENMASK(6, 0)
>> in master.h file
> Yep, you can reduce the address space.
>
>> Not sure about:
>> unsigned long addrslots[((I2C_MAX_ADDR + 1) * 2) / BITS_PER_LONG];
>> @Boris can you check this part?
> This part is still valid, no need to update it as you already updated
> I2C_MAX_ADDR.
>
> Thanks for the review.
>
> Boris

Also we can make i2c_algorithm.functionality = I2C_FUNC_SMBUS_EMUL | I2C_FUNC_I2C, and in this way we won't need ->i2c_func() and avoid the I2C_FUNC_10BIT_ADDR flag on host controller side.

Best regards,
Vitor Soares


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