Hi Stephen,

On Tue, Jul 08, 2014 at 01:00:23PM -0700, Stephen Boyd wrote:

Hi,

On MSM chips we have some efuses (called qfprom) where we store things
like calibration data, speed bins, etc. We need to read out data from
the efuses in various drivers like the cpufreq, thermal, etc. This
essentially boils down to a bunch of readls on the efuse from a handful
of different drivers. In devicetree this looks a little odd because
these drivers end up having an extra reg property (or two) that points
to a register in the efuse and some length, i.e you see this:

	thermal-sensor at 34000 {
		compatible = "sensor";
		reg = <0x34000 0x1000>, <0x10018 0xc>;
		reg-names = "sensor", "efuse_calib";
	}


I imagine in DT we want something more like this:

	efuse: efuse at 10000 {
		compatible = "efuse";
		reg = <0x10000 0x1000>;
	}

	thermal-sensor at 34000 {
		compatible = "sensor";
		reg = <0x34000 0x1000>;
		efuse = <&efuse 0x18>;
	}

We have pretty much the same things in the Allwinner SoCs. We have an
efuse directly mapped into memory, with a few informations like a MAC
address, the SoC ID, the serial number, some RSA keys for the device,
etc.

The thing is, some boards expose these informations in an external
EEPROM as well.

I started working and went quite far to create an "eeprom" framework
to handle these cases, with a dt representation similar to what you
were exposing.

https://github.com/mripard/linux/tree/eeprom-framework-at24

It was working quite well, I was about to send it, but was told that I
should all be moved to MTD, and given up on it.

Anyway, +1 for this :)

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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