linux-kernel - Re: a case for a common efuse API?

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Date:	Thu, 10 Jul 2014 17:09:45 +0200
From:	Maxime Ripard <maxime.ripard@...e-electrons.com>
To:	Grygorii Strashko <grygorii.strashko@...com>
Cc:	Stephen Boyd <sboyd@...eaurora.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Stephen Warren <swarren@...dia.com>,
	Arnd Bergmann <arnd@...db.de>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	Peter De Schrijver <pdeschrijver@...dia.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Bjorn Andersson <bjorn.andersson@...ymobile.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: a case for a common efuse API?

On Thu, Jul 10, 2014 at 06:41:55PM +0300, Grygorii Strashko wrote:
> On 07/10/2014 05:26 PM, Maxime Ripard wrote:
> >On Wed, Jul 09, 2014 at 04:32:03PM -0700, Stephen Boyd wrote:
> >>On 07/09/14 01:35, Maxime Ripard wrote:
> >>>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@...00 {
> >>>>		compatible = "sensor";
> >>>>		reg = <0x34000 0x1000>, <0x10018 0xc>;
> >>>>		reg-names = "sensor", "efuse_calib";
> >>>>	}
> >>>>
> >>>>
> >>>>I imagine in DT we want something more like this:
> >>>>
> >>>>	efuse: efuse@...00 {
> >>>>		compatible = "efuse";
> >>>>		reg = <0x10000 0x1000>;
> >>>>	}
> >>>>
> >>>>	thermal-sensor@...00 {
> >>>>		compatible = "sensor";
> >>>>		reg = <0x34000 0x1000>;
> >>>>		efuse = <&efuse 0x18>;
> >>>>	}
> 
> Why don't use "syscon" framework for your needs? (mfd/syscon.c)

Because syscon is restricted to MMIO, and not really meant to be used
for this.

Maxime

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

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