[U-Boot] [PATCH] i2c:gpio:s5p: I2C GPIO Software implementation

[Heiko Schocher]

Hello Lukasz,

Lukasz Majewski wrote:
> On Wed, 06 Jul 2011 07:56:20 +0200
> Heiko Schocher <hs at denx.de> wrote:
> 
>> Hello Mike,
>>
>> Mike Frysinger wrote:
>>> On Tuesday, July 05, 2011 08:23:41 Lukasz Majewski wrote:
>>>> This commit adds I2C software support for Samsung's S5PC110
>>>> family of processors.
>>>> The generic drivers/i2c/soft_i2c framework is used, with
>>>> routines provided by this commit.
>>> if you simply implemented the generic gpio layer (asm/gpio.h), the
>>> soft_i2c.c code already handles gluing to GPIO pins.  then you
>>> wouldnt need a sep driver at all.  you can see the bf561-ezkit
>>> already using this code. -mike
>> Yes, that was my thought too. No seperate i2c driver should be needed
>> here.
>>
>> bye,
>> Heiko
> 
> Thanks Mike and Heiko for reply.
> 
> However I've got some extra question.
> 
> In the bf651-ezkit.h file I can see the I2C definition:
> 
> #define CONFIG_SOFT_I2C
> #define CONFIG_SOFT_I2C_GPIO_SCL GPIO_PF0
> #define CONFIG_SOFT_I2C_GPIO_SDA GPIO_PF1
> 
> My concern is about the situation when SoC needs more than one Software
> I2C run via GPIO?
> 
> Please consider following scenario: 
> One sensor is connected to pins 1(SCL) and 3(SDA) and another to 4(SCL)
> and 5(SDA) in a GPIO port.
> 
> As fair as I've understood the software_i2c framework, it is supposed to
> run only one instance of GPIO I2C.
> 
> Is there any way to "instantiate" more than one I2C GPIO interface via
> software_i2c?

It should be possible (not tested), but not very nice:

First, you have to define CONFIG_I2C_MULTI_BUS and CONFIG_SYS_MAX_I2C_BUS

Then your CONFIG_SOFT_I2C_GPIO_SDA and CONFIG_SOFT_I2C_GPIO_SCL
should look something like this:

#define CONFIG_SOFT_I2C_GPIO_SDA get_sda_pin

with

int get_sda_pin(void)
{
	int busnr = i2c_get_bus_num();
	switch (busnr) {
		case 0:
			return 3;
			break;
		case 1:
			return 5;
			break;
		[...]
	}
}

Cleaner would be to get the i2c multibus branch to mainline, see:
http://git.denx.de/?p=u-boot/u-boot-i2c.git;a=shortlog;h=refs/heads/multibus_v2

bye,
Heiko
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