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

Heiko Schocher
2014-11-19T13:08:10Z

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 ...

> If platform data is supported someday, that's OK.

Patches welcome ... I have this on my ToDo list, but find currently
no time ...

bye,
Heiko
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