[U-Boot] [PATCH V3] cmd_i2c: Provide option for bulk 'i2c write' in one transaction

[Lubomir Popov]

Hi Simon,

> Hi,
>
> On 30 January 2015 at 10:56, Lubomir Popov <lpopov at mm-sol.com> wrote:
>> I2C chips do exist that require a write of some multi-byte data to occur in
>> a single bus transaction (aka atomic transfer), otherwise either the write
>> does not come into effect at all, or normal operation of internal circuitry
>> cannot be guaranteed. The current implementation of the 'i2c write' command
>> (transfer of multiple bytes from a memory buffer) in fact performs a separate
>> transaction for each byte to be written and thus cannot support such types of
>> I2C slave devices.
>>
>> This patch provides an alternative by allowing 'i2c write' to execute the
>> write transfer of the given number of bytes in a single bus transaction if
>> the '-s' option is specified as a final command argument. Else the current
>> re-addressing method is used.
>>
>> Signed-off-by: Lubomir Popov <l-popov at ti.com>
>> ---
>> Changes in V3:
>> Rebased on current master.
>> Changes in V2:
>> The option to use bulk transfer vs re-addressing is implemented as a run-time
>> command argument. V1 used conditional compilation through a board header
>> definition.
>>
>>  common/cmd_i2c.c |   39 ++++++++++++++++++++++++++++++---------
>>  1 file changed, 30 insertions(+), 9 deletions(-)
>
> What platform are you testing on?
TI OMAP/ARM, in particular the J6Eco EVM (DRA726) where we have a
I2C chip that requires this patch for proper operation of some of
its functions.
>
> It seems like you could implement this using driver model - just set
> or clear the DM_I2C_CHIP_WR_ADDRESS flag.
You are right, I could if I were sure that the DM is/shall be supported
by all TI platforms and that I would not break anything now, about which
I'm not... :( I'm looping in Tom here.
Heiko had asked me just to rebase on current mainline, so that the patch
applies cleanly, and that was what I did :)
>
> That would solve the problem of existing platforms, since they could
> be tested when converted to driver model.
>
> So what do you think about adjusting this patch to move the '#ifdef
> CONFIG_DM_I2C' outside the while loop, and set the flag instead?
> Although then your feature would only be available for driver model.
When/if the DM shall be supported by TI platforms.

Tom, do we have the DM enabled for any board, so that this could be
tested?

>
> Regards,
> Simon
>

Best regards,
Lubo