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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=no 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 5761EC07E9B for ; Tue, 20 Jul 2021 23:20:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3423B610D2 for ; Tue, 20 Jul 2021 23:20:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234445AbhGTWip (ORCPT ); Tue, 20 Jul 2021 18:38:45 -0400 Received: from foss.arm.com ([217.140.110.172]:40802 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234240AbhGTWiE (ORCPT ); Tue, 20 Jul 2021 18:38:04 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 22F281FB; Tue, 20 Jul 2021 16:18:40 -0700 (PDT) Received: from slackpad.fritz.box (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 855D03F694; Tue, 20 Jul 2021 16:18:38 -0700 (PDT) Date: Wed, 21 Jul 2021 00:18:03 +0100 From: Andre Przywara To: Benjamin Herrenschmidt Cc: Ard Biesheuvel , Matt Mackall , Herbert Xu , Linux Crypto Mailing List , Linux ARM , Linux Kernel Mailing List , Mark Brown , Will Deacon , Ali Saidi , Jon Nettleton Subject: Re: [PATCH v2] hwrng: Add Arm SMCCC TRNG based driver Message-ID: <20210721001803.303dfba1@slackpad.fritz.box> In-Reply-To: References: <20210720152158.31804-1-andre.przywara@arm.com> <20210720171631.071f84f5@slackpad.fritz.box> Organization: Arm Ltd. X-Mailer: Claws Mail 3.17.1 (GTK+ 2.24.31; x86_64-slackware-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 21 Jul 2021 08:02:42 +1000 Benjamin Herrenschmidt wrote: Hi, > On Tue, 2021-07-20 at 17:16 +0100, Andre Przywara wrote: > > Yes, a similar idea was already brought up before. I think there is even > > the potential for something like an artificial SMCCC "bus", where those > > services presentable as devices could be auto-detected (by checking > > known function IDs), the respective drivers would then probe > > automatically? > > Sounds like a boot time killer... How so? To be clear, at the moment there is basically just the TRNG service we would probe for, maybe FF-A, then adding as we go. But in any case it would be just a handful, and querying is very quick (SMC/HVC, then just a switch/case on the other side, and ERET). Is there any particular scenario you are concerned about? Quick starting guests? > can we instead describe them in DT and/or ACPI ? I think part of the idea of SMCCC is that it does NOT need firmware advertisement, but can instead be discovered, through a safe interface. Cheers, Andre