linux-kernel - Re: [PATCH v7 0/9] Add simple NVMEM Framework via regmap.

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Date:	Mon, 13 Jul 2015 22:11:10 +0200 (CEST)
From:	Stefan Wahren <stefan.wahren@...e.com>
To:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-arm-kernel@...ts.infradead.org
Cc:	wxt@...k-chips.com, linux-api@...r.kernel.org,
	Rob Herring <robh+dt@...nel.org>,
	Kumar Gala <galak@...eaurora.org>, arnd@...db.de,
	sboyd@...eaurora.org, s.hauer@...gutronix.de,
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	mporter@...sulko.com, pantelis.antoniou@...sulko.com,
	ezequiel@...guardiasur.com.ar, Mark Brown <broonie@...nel.org>,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v7 0/9] Add simple NVMEM Framework via regmap.

Hi Srinivas,

> Srinivas Kandagatla <srinivas.kandagatla@...aro.org> hat am 13. Juli 2015 um
> 21:35 geschrieben:
>
> On 13/07/15 19:54, Stefan Wahren wrote:
> > Hi Srinivas,
> >
> >> [...]
> >>
> >> Providers APIs:
> >> nvmem_register/unregister();
> >
> > How do i get the cell info from the devicetree into the nvmem_config?
> >
> Not sure what is the real use-case here, But this is how it is supposed
> to work.
>
> cellinfo in nvmem_config is used to pass cell information in non-dt
> style to the core. The core would parse it and convert into nvmem-cells.
> Am not sure why would you want to do other way round. Could you explain
> the real use case here?
>

my question comes from porting mxs_ocotp to NVMEM framework.

Here is the devicetree part:

ocotp: ocotp@...2c000 {
	compatible = "fsl,imx28-ocotp", "fsl,ocotp";
	#address-cells = <1>;
	#size-cells = <1>;
	reg = <0x8002c000 0x2000>;
	clocks = <&clks 25>;
	read-only;
				
	/* Data cells */
	ocotp_customer: costumer@20 {
		reg = <0x20 0x10>;
	};

	ocotp_rom0: rom0@1a0 {
		reg = <0x1a0 0x4>;
	};
};

After calling nvmem_register() in the provider driver [1] no data cell is
registered. So
i looked at the core code and i thought that retrieving the cell info and put it
into the nvmem_config
is job of the provider driver.

Did i missed something?

[1] -
https://github.com/lategoodbye/fsl_ocotp/commit/7c98e19755b69f761885b0e1ceb2c258a7c47ade

>
>
> >
> ...
>
> >> userspace interface: binary file in /sys/bus/nvmem/devices/*/nvmem
> >>
> >> ex:
> >> hexdump /sys/bus/nvmem/devices/qfprom0/nvmem
> >>
> >> 0000000 0000 0000 0000 0000 0000 0000 0000 0000
> >> *
> >> 00000a0 db10 2240 0000 e000 0c00 0c00 0000 0c00
> >> 0000000 0000 0000 0000 0000 0000 0000 0000 0000
> >> ...
> >> *
> >> 0001000
> >
> > Since we're entering userspace the behavior should be clear.
> >
> > How do we treat register gaps? Fill them with zero?
> nvmem file would read full nvmem size which is passed to it as regmap.
> So It would dump whatever the provider returns.

Sure, but wouldn't it be nice if different provider behave the same?

>
>
> --srini
> >
> > Best regards
> > Stefan
> >
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