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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2821AC54EBD for ; Mon, 9 Jan 2023 04:38:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236932AbjAIEiq convert rfc822-to-8bit (ORCPT ); Sun, 8 Jan 2023 23:38:46 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45944 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236941AbjAIEh6 (ORCPT ); Sun, 8 Jan 2023 23:37:58 -0500 Received: from fd01.gateway.ufhost.com (fd01.gateway.ufhost.com [61.152.239.71]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8604513E9E; Sun, 8 Jan 2023 20:33:34 -0800 (PST) Received: from EXMBX166.cuchost.com (unknown [175.102.18.54]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "EXMBX166", Issuer "EXMBX166" (not verified)) by fd01.gateway.ufhost.com (Postfix) with ESMTP id 9D36224DFF7; Mon, 9 Jan 2023 12:33:27 +0800 (CST) Received: from EXMBX168.cuchost.com (172.16.6.78) by EXMBX166.cuchost.com (172.16.6.76) with Microsoft SMTP Server (TLS) id 15.0.1497.42; Mon, 9 Jan 2023 12:33:27 +0800 Received: from EXMBX168.cuchost.com (172.16.6.78) by EXMBX168.cuchost.com (172.16.6.78) with Microsoft SMTP Server (TLS) id 15.0.1497.42; Mon, 9 Jan 2023 12:33:27 +0800 Received: from EXMBX168.cuchost.com ([fe80::3c2d:dee5:4938:3fc4]) by EXMBX168.cuchost.com ([fe80::3c2d:dee5:4938:3fc4%16]) with mapi id 15.00.1497.044; Mon, 9 Jan 2023 12:33:27 +0800 From: JiaJie Ho To: Herbert Xu CC: Olivia Mackall , Rob Herring , Krzysztof Kozlowski , Emil Renner Berthing , Conor Dooley , "linux-crypto@vger.kernel.org" , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-riscv@lists.infradead.org" Subject: RE: [PATCH v2 2/3] hwrng: starfive - Add TRNG driver for StarFive SoC Thread-Topic: [PATCH v2 2/3] hwrng: starfive - Add TRNG driver for StarFive SoC Thread-Index: AQHZGoveBWEVWeSp5UqGtlmGFQKs8K6QmY4AgATZceD//3/RgIAAj3Zg//+ATgCAAIa+sA== Date: Mon, 9 Jan 2023 04:33:26 +0000 Message-ID: References: <20221228071103.91797-1-jiajie.ho@starfivetech.com> <20221228071103.91797-3-jiajie.ho@starfivetech.com> <7c2cc6e9cdf241318fc73162a5ec221d@EXMBX168.cuchost.com> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [202.190.108.220] x-yovoleruleagent: yovoleflag Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org > -----Original Message----- > From: Herbert Xu > Sent: 9 January, 2023 12:00 PM > To: JiaJie Ho > Cc: Olivia Mackall ; Rob Herring ; > Krzysztof Kozlowski ; Emil Renner > Berthing ; Conor Dooley ; > linux-crypto@vger.kernel.org; devicetree@vger.kernel.org; linux- > kernel@vger.kernel.org; linux-riscv@lists.infradead.org > Subject: Re: [PATCH v2 2/3] hwrng: starfive - Add TRNG driver for StarFive > SoC > > On Mon, Jan 09, 2023 at 03:41:14AM +0000, JiaJie Ho wrote: > > > > The average wait time is around 20 microseconds. > > I measured from writel cmd to wait_for_completion done. > > Do you know of an upper bound? E.g., if we limit it to 40us how many > requests would fail on average? > I don't have the upper bound. I ran the rngtest with 1000 blocks, none of the wait time exceeded 30us. > Having a maximum delay of 40us would be OK with wait == 0. So you could > implement it in a way such that if the wait time exceeded 40us then you > return if wait == 0, otherwise you can wait longer. > I'll do this then. Thanks Jia Jie