linux-kernel - Re: [PATCH 2/3] hwrng: stm32 - add support for STM32 HW RNG

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAMTL27HvK3H64O2qA4hhjHOmgkJfQZO95-BnmJL7tyd+TKhz0w@mail.gmail.com>
Date:	Sun, 11 Oct 2015 20:15:01 +0100
From:	Daniel Thompson <daniel.thompson@...aro.org>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	Lee Jones <lee.jones@...aro.org>, Matt Mackall <mpm@...enic.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Patch Tracking <patches@...aro.org>,
	Linaro Kernel Mailman List <linaro-kernel@...ts.linaro.org>,
	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>
Subject: Re: [PATCH 2/3] hwrng: stm32 - add support for STM32 HW RNG

On 5 October 2015 at 10:22, Daniel Thompson <daniel.thompson@...aro.org> wrote:
> On 4 October 2015 at 11:32, Linus Walleij <linus.walleij@...aro.org> wrote:
>> On Sat, Oct 3, 2015 at 10:35 PM, Daniel Thompson
>> 3. I took out the datasheet for Nomadik STn8820 and it seems that
>> the hardware is very similar to what this driver is trying to drive.
>> CR, SR and DR are in the same place, can you check if you also even
>> have the PrimeCell magic in the words at offset 0xfe0 thru 0xffc?
>
> The register window for the STM32 RNG is only 0x400 (and I'll fix the
> DT for v2 ;-) ) so the STM32 version isn't primecell-like.
>
>
>> In any case it seems likely that this driver should supercede and replace
>> drivers/char/hw_random/nomadik-rng.c
>> still using the PrimeCell bus, and if it doesn't have the PrimeCell
>> IDs in hardware, this can be specified in the device tree using
>> arm,primecell-periphid = <0x000805e1>; in the node if need be.
>> The in-tree driver is dangerously simple and assume too much IMO.
>
> Not sure about this, but I'll take a closer look. There is a certain
> family resemblance in the register set but there are significant
> differences in data transfer between the Nomadik and STM32 hardware.

Having looked at this I don't really think we would gain very much
from combining these drivers. The cells have different (albeit
slightly similar) register layouts, different ways to transfer data
(16- versus 32-bit) and different ways to report test/report incorrect
clocking. In the case of the RNG the differences therefore span the
entire of its feature set.

I think combining them just results in two drivers that happen to
share a file and I dislike having to add "fake" information to the
devicetree to make it hang together.

Is that convincing for you?


Daniel.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/