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

[Heiko Schocher]

Hello Simon,

Am 20.11.2014 18:31, schrieb Simon Glass:
> Hi Heiko,
>
> On 19 November 2014 13:08, Heiko Schocher <hs at 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 at 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.

Yes, but we have architectures without FDT support yet ... and we boot
also non linux OSes ...

>>> 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.

Great, but powerpc should work with DT too...

bye,
Heiko
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