[U-Boot] [PATCH v2] ARM: imx6: DHCOM i.MX6 PDK: Switch to DM for I2C

[Marek Vasut]

On 7/8/19 10:21 AM, Ludwig Zenz wrote:
> On 7/5/19 14:24 PM, Marek Vasut wrote:
>>
>> On 7/5/19 12:46 PM, Ludwig Zenz wrote:
>> [...]
>>
>>>  static int setup_dhcom_mac_from_fuse(void)
>>>  {
>>> +	struct udevice *dev;
>>>  	unsigned char enetaddr[6];
>>>  	int ret;
>>>  
>>> @@ -228,13 +142,13 @@ static int setup_dhcom_mac_from_fuse(void)
>>>  		return 0;
>>>  	}
>>>  
>>> -	ret = i2c_set_bus_num(2);
>>> +	ret = uclass_first_device_err(UCLASS_I2C_EEPROM, &dev);
>>
>> What about uclass_find_device_by_of_node() ? Then you can specify a
>> stable fixed hardware path to the EEPROM, and no matter how many EEPROMs
>> someone connects to the board, this code won't be affected.
>>
>> [...]
>>
> 
> The function uclass_find_device_by_ofnode() is used only once in U-Boot and the
> declaration is in 'include/dh/uclass-interal.h'. I found a similar function called
> uclass_get_device_by_ofnode(), which is used in several places.
> 
> Unfortunately I didn't manage to work out the difference. 
> What I don't like is that the former is from uclass-internal.h.
>                                                     --------
> 
> A possible implementation would be as follows:
> 
> [...]
>         struct udevice *dev;
> 	ofnode eeprom;
> 	unsigned char enetaddr[6];
> 	int ret;
> 
> [...]
> 
> 	eeprom = ofnode_path("/soc/aips-bus at 2100000/i2c at 21a8000/eeprom at 50");
> 	if (!ofnode_valid(eeprom)) {
> 		printf("Invalid hardware path to EEPROM!\n");
> 		return -ENODEV;
> 	}
> 
> 	ret = uclass_get_device_by_ofnode(UCLASS_I2C_EEPROM, eeprom, &dev);
> 	if (ret) {
> 		printf("Cannot find EEPROM!\n");
> 		return ret;
> 	}
> 
> 	ret = i2c_eeprom_read(dev, 0xfa, enetaddr, 0x6);
> 	if (ret) {
> 		printf("Error reading configuration EEPROM!\n");
> 		return ret;
> 	}
> 
> [...]
> 
> We're lucky here that the Duallite and Quad mapped the I2C controllers on the same addresses.
> But I'm not sure if this is really a good implementation.
> 
> Would it be advantageous to make a device tree entry in /chosen for the MAC EEPROM instead?
> Then we could do something like:
> 
> eeprom = ofnode_get_chosen_node("mac,eeprom");
> 
> 
> I'd be happy to get feedback on that.

The correct solution would be to add some sort of link from the ethernet
MAC to the EEPROM, maybe via nvmem or somesuch. But I don't think U-Boot
implements that.

I don't have any better suggestion, maybe someone else does.

-- 
Best regards,
Marek Vasut