H3 eFuse usage

[andormaybe]

Hello,

 

I am new to this forum and I would like to ask a question concerning Allwinner's H3 eFuse feature. Studying the chip's datasheet, I saw that there is this eFuse feature, which would be mightily handy for my to-come project using H3 or H2+ hardware (OPi Zero to be specific) as a basis in combination with Armbian (which I find fantastic btw). Is there any driver available for this feature? I couldn't find any info on the net so far. Thx a lot for your time and efforts.

 

BR,

 

andormaybe

[martinayotte]

On A20, the eFuse can be read since the EEPROM is defined in the DTS.

But it doesn't seems to be defined in the H3.

 

Some details for eFuse can be found here : http://linux-sunxi.org/SID_Register_Guide

 

EDIT : I've added the following on H3 OPiPC DT and got it working :

                sid: eeprom@01c14200 {
                        compatible = "allwinner,sun7i-a20-sid";  
                        reg = <0x01c14200 0x200>;
                };

To read content :

hexdump -C /sys/devices/platform/soc/1c14200.eeprom/sunxi-sid0/nvmem

[andormaybe]

Fantastic work!

 

What I am still not quite sure about is whether or not this is really an EEPROM or a OTP fuse memory. I looked up the term 'eFuse' and understood from various descriptions, that it is in general a OTP mechanism. Which would be OK. But it could be more handy if it were an EEPROM. My OPi PC and Zero are still on their way from Asia to my place, so I can't try it out myself yet, if the thing is reprogrammable. 

[martinayotte]

Yes, I think it is actually an EEPROM, but it is not sure the write procedure is well known or even implemented in current mainline kernel.

If you really need some EEPROM for your own purposes, the PiZero has an SPIFlash on board, and for other boards, some I2C EEPROM or SPIFlash can be easily added externally.

[zador.blood.stained]

Judging by the discussions I think it's OTP, not EEPROM. And it's mostly useful for "Secure boot" or storing SoC serial number, for storing anything other it may be better to connect any cheap I2C EEPROM or use SPI flash