[U-Boot] [PATCH v2 0/17] dm: Add I2C support and convert sandbox, tegra

Simon Glass
2014-11-20T17:31:40Z

Hi Heiko,

On 19 November 2014 13:08, Heiko Schocher <hs@denx.de> wrote:
> Hello Masahiro,
>
> Am 19.11.2014 09:27, schrieb Masahiro Yamada:
>
>> Hi Simon,
>>
>>
>>
>> On Tue, 11 Nov 2014 10:46:16 -0700
>> Simon Glass <sjg@chromium.org> wrote:
>>
>>>
>>> This series adds I2C support to driver model. It has become apparent that
>>> this is a high priority as it is widely used. It follows along to some
>>> extent from the SPI conversion.
>>>
>>> Several changes are made from the original I2C implementations.
>>>
>>> Firstly it is not necessary to specify the chip address with every call,
>>> since each chip knows its own address - it is stored in struct
>>> dm_i2c_chip
>>> which is attached to each chip on the I2C bus. However, this information
>>> *is* passed to the driver since I presume most drivers need it and it
>>> would
>>> be cumbersome to look up in every call.
>>>
>>> Secondly there is no concept of a 'current' I2C bus so all associated
>>> logic
>>> is removed. With driver model i2c_set_bus_num() and i2c_get_bus_num() are
>>> not available. Since the chip device specifies both the bus and the chip
>>> address, there is no need for this concept. It also causes problems when
>>> one driver changes the current bus and forgets to change it back.
>>>
>>> Thirdly initialisation is handled by driver model's normal probe() method
>>> on each device so there should be no need for i2c_init_all(), i2c_init(),
>>> i2c_init_board(), i2c_board_late_init() and board_i2c_init().
>>>
>>> I2C muxes are not yet supported. To support these we will need to
>>> maintain
>>> state of the current mux settings to avoid resetting every mux every
>>> time.
>>> Probably we need to add a sandbox I2C mux driver to permit testing of
>>> this.
>>> This can probably be done later.
>>>
>>> Platform data is not yet supported either, only device tree. The
>>
>>
>> This statement implies that platform data will (should) be supported
>> in the future, I think.
>
>
> There was a discussion on the ELCE2014 and I think, I thought such
> a thread also on the list, if we should only support device tree with
> DM ...
>
>> As you know, I have a strong belief that device tree should be left
>> optional.
>
>
> Yes, I think in this direction too ... as I do not know, if
> all archs ever support DT ... and in the SPL case we should
> have a memory friendlier option too ...

My feeling is that if Linux uses FDT for a platform (e.g. ARM) we
should do so in U-Boot.

>
>> If platform data is supported someday, that's OK.
>
>
> Patches welcome ... I have this on my ToDo list, but find currently
> no time ...

I'm going to play around with a PPC board at some point, so will see
what happens there.

Regards,
Simon