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

[Ludwig Zenz]

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.

regards,
Ludwig Zenz