[U-Boot] question about software i2c multi instance

[Przemyslaw Marczak <p.marczak@samsung.com>]

Hello Bo,


On 03/23/2015 09:36 AM, Bo Shen wrote:
> Hi Lukasz,
>
> On 03/23/2015 04:28 PM, Lukasz Majewski wrote:
>> Hi Bo,
>>
>>> Hi Heiko,
>>>     After check the software i2c code, I found it can not support
>>> multi instances, although it has I2C_SOFT_DECLARATIONS2,
>>> I2C_SOFT_DECLARATIONS3, I2C_SOFT_DECLARATIONS4.
>>>     Because, when do GPIO operation, there is only one pair of
>>> CONFIG_SOFT_I2C_GPIO_SCL and CONFIG_SOFT_I2C_GPIO_SDA.
>>>     So, if want to support multi instances, it needs to extend the
>>> GPIO configuration for SCL/SDA, am I right?
>>
>> Some time ago we had a similar problem with SW I2C code. Please look
>> into Samsung's trats board implementation.
>>
>> However, such approach might be outdated, since Przemek is working on
>> porting this functionality to device model:
>>
>> https://patchwork.ozlabs.org/patch/448460/
>
> Thanks for your information.
> Now, I just do it as following to make it work. For next step, I will
> try to switch to use DM.
>
> --->8---
> diff --git a/drivers/i2c/soft_i2c.c b/drivers/i2c/soft_i2c.c
> index db9b402..b9cfbb8 100644
> --- a/drivers/i2c/soft_i2c.c
> +++ b/drivers/i2c/soft_i2c.c
> @@ -126,6 +126,13 @@ DECLARE_GLOBAL_DATA_PTR;
>   #define PRINTD(fmt,args...)
>   #endif
>
> +#ifdef I2C_READ_ADAP
> +static int soft_i2c_read_sda(void)
> +{
> +       I2C_READ_ADAP;
> +}
> +#endif
> +
>   /*-----------------------------------------------------------------------
>    * Local functions
>    */
> @@ -256,7 +263,11 @@ static int write_byte(uchar data)
>          I2C_SCL(1);
>          I2C_DELAY;
>          I2C_DELAY;
> +#ifdef I2C_READ_ADAP
> +       nack = soft_i2c_read_sda();
> +#else
>          nack = I2C_READ;
> +#endif
>          I2C_SCL(0);
>          I2C_DELAY;
>          I2C_ACTIVE;
> @@ -286,7 +297,11 @@ static uchar read_byte(int ack)
>                  I2C_SCL(1);
>                  I2C_DELAY;
>                  data <<= 1;
> +#ifdef I2C_READ_ADAP
> +               data |= soft_i2c_read_sda();
> +#else
>                  data |= I2C_READ;
> +#endif
>                  I2C_DELAY;
>          }
>          send_ack(ack);
> ---8<---
>
> Thanks again.
>
> Best Regards,
> Bo Shen
>
>

Please look into the Trats2 board code in:

board/samsung/trats2/trats2.c lines 130-145
include/configs/trats2.h lines 180-185

It doesn't require i2c driver modifications. But anyway I recommend to 
use the code of my patches, which Lukasz mentioned.

Best regards,
-- 
Przemyslaw Marczak
Samsung R&D Institute Poland
Samsung Electronics
p.marczak at samsung.com