From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 53DD023371F; Tue, 3 Jun 2025 15:53:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748966016; cv=none; b=K2GbPqkWkcHSJnGZN9ADWN85Y8ila8MMVwFDrkw4FzfRDFs8qkfelv8S+hMPNgKZWbL1rrdZMSOMIeyJCWKvbFyp8zpfU/8S3Ug7xBDoGmHUgx6mb0FRD4jJehnFUPPbQjjAiRXlneigAoBm0dRjChkLfU3ENn8N8EG1YSydhbE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748966016; c=relaxed/simple; bh=ujm9MuI/e9VolCk4e0eb1/DBEfCNPcM/FoVXZk/NeXE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=a0dQ27oGny56PKOojL9HTNY16x08Dv6mc7sakLzhs3HoXpKlw7d0PRbRLQ3APLb7JQCUEuqqSJqotywHyw0Hq3vnXhjV4RYpGHScPwYv09h7s23vJ5BE/KgwEO+SScyD4oHyjP9KDxhTmv30Dm6Ddbb3MVzAtGg8XAO7PfL2mVc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=bUPrDeKN; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="bUPrDeKN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C608BC4CEED; Tue, 3 Jun 2025 15:53:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1748966015; bh=ujm9MuI/e9VolCk4e0eb1/DBEfCNPcM/FoVXZk/NeXE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=bUPrDeKN6S5ATwkVju4UuE4PGM3yT9mWmZc47U6x6ymNepe8Gv/IW133YFTeBEo/T mnbFsDX11nCCrBnr+7UZXR+8fDAiEeeDkOBC6Voi4Mr+t8pGTQemHkMHUQYu1HOHPV iSiMGus9LNTzHAQnu/Eq4CxyS8Cxd9WFY4k29P2UGrirQARIhAo6hXLRzZ5vyksPjD LRYWBBdAF2u64Nt+OvCOJEPXAI2wu1MpPPMHTNRPI8SZBa9N7eJqhZ/pXj5JuwcyLw wFSM/vfOvFIBFt229CJhraqS3Q0mpDEWujvVM3Y2J21iiiCQc9K6romdITw/Snp9Ez uP9JCowCZNdWA== Date: Tue, 3 Jun 2025 17:53:26 +0200 From: Lorenzo Pieralisi To: Rob Herring Cc: Peter Maydell , Krzysztof Kozlowski , Marc Zyngier , Thomas Gleixner , Conor Dooley , Catalin Marinas , Will Deacon , andre.przywara@arm.com, Arnd Bergmann , Sascha Bischoff , Timothy Hayes , "Liam R. Howlett" , Mark Rutland , Jiri Slaby , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, suzuki.poulose@arm.com Subject: Re: [PATCH v4 01/26] dt-bindings: interrupt-controller: Add Arm GICv5 Message-ID: References: <20250513-gicv5-host-v4-0-b36e9b15a6c3@kernel.org> <20250513-gicv5-host-v4-1-b36e9b15a6c3@kernel.org> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Tue, Jun 03, 2025 at 10:15:25AM -0500, Rob Herring wrote: > On Tue, Jun 3, 2025 at 2:48 AM Lorenzo Pieralisi wrote: > > > > On Thu, May 29, 2025 at 02:17:26PM +0100, Peter Maydell wrote: > > > On Thu, 29 May 2025 at 13:44, Lorenzo Pieralisi wrote: > > > > > > > > [+Andre, Peter] > > > > > > > > On Tue, May 13, 2025 at 07:47:54PM +0200, Lorenzo Pieralisi wrote: > > > > > + reg: > > > > > + minItems: 1 > > > > > + items: > > > > > + - description: IRS control frame > > > > > > > > I came across it while testing EL3 firmware, raising the topic for > > > > discussion. > > > > > > > > The IRS (and the ITS) has a config frame (need to patch the typo > > > > s/control/config, already done) per interrupt domain supported, that is, > > > > it can have up to 4 config frames: > > > > > > > > - EL3 > > > > - Secure > > > > - Realm > > > > - Non-Secure > > > > > > > > The one described in this binding is the non-secure one. > > > > > > > > IIUC, everything described in the DT represents the non-secure address > > > > space. > > > > > > The dt bindings do allow for describing Secure-world devices: > > > Documentation/devicetree/bindings/arm/secure.txt has the > > > details. We use this in QEMU so we can provide a DTB to > > > guest EL3 firmware that tells it where the hardware is > > > (and which EL3 can then pass on to an NS kernel). It would > > > be helpful for the GICv5 binding to be defined in a way that > > > we can do this for a GICv5 system too. > > > > It would be good to understand what DT {should/should not} describe and > > whether this DT usage to configure firmware is under the DT maintainers > > radar or it is an attempt at reusing it to avoid implementing a > > configuration scheme. > > > > Rob, Krzysztof, > > > > Any thoughts on the matter please ? > > I'm all for firmware using DT, but using a single DT for all > components with an ABI between all components is an impractical dream. > You can take that a step further even with a single DT for all > processors in a system (aka System DT). Ultimately, the DT is a view > of the system for a client (OS). Different views may need different > DTs. Specifically, for IRS/ITS frames then - what the current schema does is correct, namely, it does _not_ spell out whether the IRS/ITS config frame is NS/S/Realm/Root interrupt domain, that's information that the client implicitly assumes. Are we OK with this approach ? This would leave open the possibility of having a DT per security-state. If in the DT schema I define eg reg -> "IRS NS config frame" by construction the binding can't be used for anything else. Please let me know if we are in agreement on this matter. Lorenzo > u-boot and Linux sharing a DT makes sense as they have the same world > view. Secure and NS not so much. > > > [...] > > > > > The tempting thing to do is to have regs[] list the frames > > > in some given order, but the spec makes them not simple > > > supersets, allowing all of: > > > * NS > > > * S > > > * NS, S, EL3 > > > * NS, Realm, EL3 > > > * NS, Realm, S, EL3 > > > > Maybe reg-names can help ? Even though first we need to understand > > what resources should be described in DT. > > > > Current bindings are reviewed and I am not keen on dragging this > > discussion on forever - the information the kernel requires is there, > > I'd like to bring this to a close. > > > > Thanks, > > Lorenzo > > > > > > > > secure.txt says: > > > # The general principle of the naming scheme for Secure world bindings > > > # is that any property that needs a different value in the Secure world > > > # can be supported by prefixing the property name with "secure-". So for > > > # instance "secure-foo" would override "foo". > > Today I would say a 'secure-' prefix is a mistake. To my knowledge, > it's never been used anyways. But I don't have much visibility into > what secure world firmware is doing. > > > > > > > So maybe we could have > > > reg : the NS frame(s) > > > secure-reg : the S frame(s) > > > realm-reg : the Realm frame(s) > > > root-reg : the EL3 frame(s) > > Here's why. It really doesn't scale. > > Rob