From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 079A3C32771 for ; Thu, 23 Jan 2020 01:25:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C09B521569 for ; Thu, 23 Jan 2020 01:25:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=neuralgames.com header.i=@neuralgames.com header.b="JL4ECqtM" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725911AbgAWBZi (ORCPT ); Wed, 22 Jan 2020 20:25:38 -0500 Received: from kross.rwserver.com ([69.13.37.146]:43796 "EHLO kross2019.rwserver.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726004AbgAWBZi (ORCPT ); Wed, 22 Jan 2020 20:25:38 -0500 Received: from localhost (localhost [127.0.0.1]) by kross2019.rwserver.com (Postfix) with ESMTP id 1A6B7B39EF; Wed, 22 Jan 2020 19:25:37 -0600 (CST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=neuralgames.com; h=user-agent:message-id:references:in-reply-to:subject:subject :from:from:date:date:content-transfer-encoding:content-type :content-type:mime-version; s=default; t=1579742736; x= 1581557137; bh=Rk/Ounh4vmGF04q+59h2/BCGllWhaNrGkT3gZmCD4gg=; b=J L4ECqtM8PRZ4hdC/SzbrrjBJW1nz42HjpM5FgtmftoIl4EvXxcRCHbBKS+YhMwqB 6Eu/gtTTxKx56BePYs5714M1h0QpcKjlh3tyJnJ2fTjxMUUUFDCzxDESp+FZo/k7 XPSQJGUp0igogDccsH5O87reiPvJc6ApOq/i1bo/CQ= X-Virus-Scanned: Debian amavisd-new at kross2019.rwserver.com Received: from kross2019.rwserver.com ([127.0.0.1]) by localhost (kross2019.rwserver.com [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id IFigBOrF8czw; Wed, 22 Jan 2020 19:25:36 -0600 (CST) Received: from rwserver.com (localhost [IPv6:::1]) (Authenticated sender: linux@neuralgames.com) by kross2019.rwserver.com (Postfix) with ESMTPA id 7723FB39EE; Wed, 22 Jan 2020 19:25:36 -0600 (CST) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Wed, 22 Jan 2020 19:25:36 -0600 From: linux@neuralgames.com To: Joel Stanley Cc: Matt Mackall , Herbert Xu , Rob Herring , Mark Rutland , Andrew Jeffery , Linux Crypto Mailing List , devicetree , Linux ARM , linux-aspeed , Linux Kernel Mailing List Subject: Re: [PATCH 1/2] hwrng: Add support for ASPEED RNG In-Reply-To: References: <20200120150113.2565-1-linux@neuralgames.com> Message-ID: <4446ffb694c7742ca9492c7360856789@neuralgames.com> X-Sender: linux@neuralgames.com User-Agent: Roundcube Webmail/1.3.8 Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org Hi Joel, On 2020-01-20 19:53, Joel Stanley wrote: > Hi, > > On Mon, 20 Jan 2020 at 15:12, Oscar A Perez > wrote: >> >> This minimal driver adds support for the Hardware Random Number >> Generator >> that comes with the AST2400/AST2500/AST2600 SOCs from AspeedTech. >> >> The HRNG on these SOCs uses Ring Oscillators working together to >> generate >> a stream of random bits that can be read by the platform via a 32bit >> data >> register. > > Thanks for the patch. > > We've been using the timeriomem-rng driver for the past few years on > aspeed hardware. You can see how that's set up by looking at > arch/arm/boot/dts/aspeed-g{4,5,6}.dtsi > > I suggest we continue to use the generic driver. > > Cheers, > > Joel > > > Thanks for reviewing the patch. The RNG on Aspeed hardware allows eight different modes for combining its four internal Ring Oscillators that together generate a stream of random bits. However, the timeriomem-rng driver does not allow for mode selection so, the Aspeed RNG with this generic driver runs always on mode 'seven' (The default value for mode according to the AspeedTech datasheets). I've performed some testings on this Aspeed RNG using the NIST Statistical Test Suite (NIST 800-22r1a) and, the results I got show that the default mode 'seven' isn't producing the best entropy and linear rank when compared against the other modes available on these SOCs. On the other hand, the driver that I'm proposing here allows for mode selection which would help improve the random output for those looking to get the best out of this Aspeed RNG. Thanks and regards, Oscar A Perez >> >> Signed-off-by: Oscar A Perez >> --- >> .../devicetree/bindings/rng/aspeed-rng.yaml | 90 >> +++++++++++++++++++ >> 1 file changed, 90 insertions(+) >> create mode 100644 >> Documentation/devicetree/bindings/rng/aspeed-rng.yaml >> >> diff --git a/Documentation/devicetree/bindings/rng/aspeed-rng.yaml >> b/Documentation/devicetree/bindings/rng/aspeed-rng.yaml >> new file mode 100644 >> index 000000000000..06070ebe1c33 >> --- /dev/null >> +++ b/Documentation/devicetree/bindings/rng/aspeed-rng.yaml >> @@ -0,0 +1,90 @@ >> +# SPDX-License-Identifier: GPL-2.0 >> +%YAML 1.2 >> +--- >> +$id: "http://devicetree.org/schemas/rng/aspeed-rng.yaml#" >> +$schema: "http://devicetree.org/meta-schemas/core.yaml#" >> + >> + >> +title: Bindings for Aspeed Hardware Random Number Generator >> + >> + >> +maintainers: >> + - Oscar A Perez >> + >> + >> +description: | >> + The HRNG on the AST2400/AST2500/AST2600 SOCs from AspeedTech uses >> four Ring >> + Oscillators working together to generate a stream of random bits >> that can be >> + read by the platform via a 32bit data register every one >> microsecond. >> + All the platform has to do is to provide to the driver the >> 'quality' entropy >> + value, the 'mode' in which the combining ROs will generate the >> stream of >> + random bits and, the 'period' value that is used as a wait-time >> between reads >> + from the 32bit data register. >> + >> + >> +properties: >> + compatible: >> + oneOf: >> + - items: >> + - enum: >> + - aspeed,ast2400-rng >> + - aspeed,ast2500-rng >> + - aspeed,ast2600-rng >> + >> + >> + reg: >> + description: >> + Base address and length of the register set of this block. >> + Currently 'reg' must be eight bytes wide and 32-bit aligned. >> + >> + maxItems: 1 >> + >> + >> + period: >> + description: >> + Wait time in microseconds to be used between reads. >> + The RNG on these Aspeed SOCs generates 32bit of random data >> + every one microsecond. Choose between 1 and n microseconds. >> + >> + maxItems: 1 >> + >> + >> + mode: >> + description: >> + One of the eight modes in which the four internal ROs (Ring >> + Oscillators) are combined to generate a stream of random >> + bits. The default mode is seven which is the default method >> + of combining RO random bits on these Aspeed SOCs. >> + >> + maxItems: 1 >> + >> + >> + quality: >> + description: >> + Estimated number of bits of entropy per 1024 bits read from >> + the RNG. Note that the default quality is zero which stops >> + this HRNG from automatically filling the kernel's entropy >> + pool with data. >> + >> + maxItems: 1 >> + >> + >> +required: >> + - compatible >> + - reg >> + - period >> + - quality >> + >> + >> +examples: >> + - | >> + rng: hwrng@1e6e2074 { >> + compatible = "aspeed,ast2500-rng"; >> + reg = <0x1e6e2074 0x8>; >> + period = <4>; >> + quality = <128>; >> + mode = <0x7>; >> + }; >> + >> + >> +... >> -- >> 2.17.1 >>