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 phobos.denx.de (phobos.denx.de [85.214.62.61]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9A680C004D4 for ; Thu, 19 Jan 2023 17:00:40 +0000 (UTC) Received: from h2850616.stratoserver.net (localhost [IPv6:::1]) by phobos.denx.de (Postfix) with ESMTP id 1B4308567F; Thu, 19 Jan 2023 18:00:37 +0100 (CET) Authentication-Results: phobos.denx.de; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: phobos.denx.de; spf=pass smtp.mailfrom=u-boot-bounces@lists.denx.de Received: by phobos.denx.de (Postfix, from userid 109) id D312485683; Thu, 19 Jan 2023 18:00:32 +0100 (CET) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by phobos.denx.de (Postfix) with ESMTP id C02AB85678 for ; Thu, 19 Jan 2023 18:00:25 +0100 (CET) Authentication-Results: phobos.denx.de; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: phobos.denx.de; spf=pass smtp.mailfrom=sudeep.holla@arm.com 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 790AA176A; Thu, 19 Jan 2023 09:01:06 -0800 (PST) Received: from bogus (unknown [10.57.77.84]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E0F323F445; Thu, 19 Jan 2023 09:00:22 -0800 (PST) Date: Thu, 19 Jan 2023 17:00:20 +0000 From: Sudeep Holla To: Simon Glass Cc: Abdellatif El Khlifi , trini@konsulko.com, achin.gupta@arm.com, xueliang.zhong@arm.com, Drew.Reed@arm.com, robh@kernel.org, jens.wiklander@linaro.org, Sudeep Holla , ilias.apalodimas@linaro.org, u-boot@lists.denx.de Subject: Re: [PATCH v8 03/10] arm_ffa: introduce Arm FF-A low-level driver Message-ID: <20230119170020.zi6rmcs35i2pn2w4@bogus> References: <20230118124923.GB631605@bill-the-cat> <20230118135932.GC631605@bill-the-cat> <20230119163157.GA18384@e121910.cambridge.arm.com> <20230119164652.llh66rapyqqej63f@bogus> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-BeenThere: u-boot@lists.denx.de X-Mailman-Version: 2.1.39 Precedence: list List-Id: U-Boot discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: u-boot-bounces@lists.denx.de Sender: "U-Boot" X-Virus-Scanned: clamav-milter 0.103.6 at phobos.denx.de X-Virus-Status: Clean On Thu, Jan 19, 2023 at 09:54:29AM -0700, Simon Glass wrote: > Hi Sudeep, > > On Thu, 19 Jan 2023 at 09:46, Sudeep Holla wrote: > > > > Thanks for the details. But IIRC this discussion is not about the FF-A bus > > and device(partitions) discovery, but the support for FF-A itself. The > > discussion is about where to have a device node to represent the existence of > > FF-A support on a platform. If we are talking about individual partitions > > (devices) in the device tree, then that is pure stupidity as it goes out > > of since with the firmware the moment a partition is added or removed in > > the firmware. > > > > IIUC, the whole discussion was around whether to use FFA_VERSION as the > > discovery mechanism for existence of FF-A support on a platform or you > > have a device node to specify the same. > > No, with respect, that is not quite the situation here. > Hmm, not sure what you mean by that. Based on your earlier response, I thought we are in agreement but you sound to differ here. Am I missing something ? > > > > Just to be clear, even if it is decided to add a device node, the > > FFA_VERSION must be used to detect the presence of FF-A support and > > return error otherwise. DT node presence is just to satisfy the design > > and must be treated as no auto-confirmation for the presence of FF-A > > support. We are just arguing the device node presence is just redundant, > > but as mentioned before it is up to U-Boot community to make a call on > > what is best. > > U-Boot driver model design already supports this. You can have a > device that binds (from DT) but will not probe because it is not > present / wrong version. Perhaps this was missed in the conversion to > Linux: > > https://u-boot.readthedocs.io/en/latest/develop/driver-model/design.html#driver-lifecycle > > So there is nothing clever needed here at all and anything you do just > adds confusion and bad precedent. > OK, I will give that a read. -- Regards, Sudeep