Re: [PATCH 1/5] dt-bindings: nvmem: add binding for Raspberry Pi OTP

From: Stefan Wahren <stefan.wahren@i2se.com>
To: Rob Herring <robh@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
	devicetree@vger.kernel.org,
	Florian Fainelli <f.fainelli@gmail.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Scott Branden <sbranden@broadcom.com>,
	Ray Jui <rjui@broadcom.com>, Eric Anholt <eric@anholt.net>,
	Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
	linux-rpi-kernel@lists.infradead.org, gregkh@linuxfoundation.org,
	bcm-kernel-feedback-list@broadcom.com,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/5] dt-bindings: nvmem: add binding for Raspberry Pi OTP
Date: Fri, 28 Dec 2018 16:46:39 +0100 (CET)	[thread overview]
Message-ID: <812144724.382117.1546011999351@email.ionos.de> (raw)
In-Reply-To: <894cfae3-43f4-f201-9b54-41114ce8107e@i2se.com>

Hi Rob,

> Stefan Wahren <stefan.wahren@i2se.com> hat am 7. Dezember 2018 um 09:10 geschrieben:
> 
> 
> Hi Rob,
> 
> Am 07.12.18 um 00:49 schrieb Rob Herring:
> > On Wed, Nov 21, 2018 at 02:11:40PM +0100, Stefan Wahren wrote:
> >> This patch adds the devicetree binding for Raspberry Pi customer OTP
> >> driver.
> >>
> >> Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
> >> ---
> >>  .../nvmem/raspberrypi,bcm2835-customer-otp.txt     | 22 ++++++++++++++++++++++
> >>  1 file changed, 22 insertions(+)
> >>  create mode 100644 Documentation/devicetree/bindings/nvmem/raspberrypi,bcm2835-customer-otp.txt
> >>
> >> diff --git a/Documentation/devicetree/bindings/nvmem/raspberrypi,bcm2835-customer-otp.txt b/Documentation/devicetree/bindings/nvmem/raspberrypi,bcm2835-customer-otp.txt
> >> new file mode 100644
> >> index 0000000..041ff17
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/nvmem/raspberrypi,bcm2835-customer-otp.txt
> >> @@ -0,0 +1,22 @@
> >> +Customer OTP Memory for Raspberry Pi
> >> +
> >> +The VC4 firmware exposes a mailbox interface that allows the ARM core
> >> +to access the customer part of the OTP memory.
> >> +
> >> +The OTP node must be a child node of the Raspberry Pi firmware node.
> >> +
> >> +Required properties :
> >> +- compatible     : Should be "raspberrypi,bcm2835-customer-otp"
> > Why do we need this child node? Can't the parent instantiate this?
> >
> > Are there OTP fields you want to expose in DT?
> 
> the customer part of the OTP is reserved (initialized with zero) for
> user who wants to use the Raspberry Pi (mostly the Compute Module) in
> their custom designs. So i cannot provide any nvmem cells yet because it
> is up to the user to define them (e.g. hardware related values like
> serial numbers, MAC addresses for additional network interfaces or
> calibration values). But yes i consider the binding and the ability to
> define nvmem cells via devicetree as a great feature.
> 
> Currently the Foundation suggests to use the mailbox interface from
> userspace [1], but i prefer a more common way like nvmem.
> 
> [1] - 
> https://www.raspberrypi.org/documentation/hardware/industrial/README.md
>

did it answer your questions?

Stefan

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