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 C3489C433F5 for ; Mon, 28 Feb 2022 12:57:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232408AbiB1M6D (ORCPT ); Mon, 28 Feb 2022 07:58:03 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46354 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233191AbiB1M5z (ORCPT ); Mon, 28 Feb 2022 07:57:55 -0500 Received: from polaris.svanheule.net (polaris.svanheule.net [IPv6:2a00:c98:2060:a004:1::200]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4EFC67804D for ; Mon, 28 Feb 2022 04:57:17 -0800 (PST) Received: from vanadium.ugent.be (vanadium.ugent.be [157.193.99.61]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: sander@svanheule.net) by polaris.svanheule.net (Postfix) with ESMTPSA id F17332A9DB5; Mon, 28 Feb 2022 13:57:14 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=svanheule.net; s=mail1707; t=1646053035; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=bapqjhLApcwzDEhybuGVU/3933XunfSW4IVKilZ7qD4=; b=pv0ZTcwUvhCAo4vxv2igrSpgiecCPZyuDI4hMokJve/s2Gdp7QcZcXzj5UohqsBwM7ZAAA eNzPSkxzaKOjLZv7DGoka7E+VKNpTHHGKC9F7+Hdagu30tmeQ4KgeCkDRLBDWQk5XnYUeI Kit+3/QQ8BzKWgnbEP71BU/7x1GRzLGMgb5uWMt2XL7CL0LW15E+ekd/P7P6XJQYLaNFOg vekTaj76LdctZmJ60lIbMjl1uhQdUpY+Qm3v2CKx0c6G6gIzcdc7Lei5D+oNAHa9DDqQh7 IoziqFLAMWxOiUJyyzseWZL1GYr1eH1qszF3viLsY/5vuvOuwXEVdEPD9kf6aA== Message-ID: <4a8dac0dc296920c6e58584d48d6eaf6644b0322.camel@svanheule.net> Subject: Re: [PATCH v5 0/4] Per-parent domains for realtek-rtl IRQ driver From: Sander Vanheule To: Marc Zyngier Cc: Rob Herring , devicetree@vger.kernel.org, Thomas Gleixner , Birger Koblitz , Bert Vermeulen , John Crispin , linux-kernel@vger.kernel.org Date: Mon, 28 Feb 2022 13:57:13 +0100 In-Reply-To: <87czjo49ht.wl-maz@kernel.org> References: <87czjo49ht.wl-maz@kernel.org> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.42.4 (3.42.4-1.fc35) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Marc, On Tue, 2022-02-15 at 12:09 +0000, Marc Zyngier wrote: > On Mon, 14 Feb 2022 18:56:57 +0000, > Sander Vanheule wrote: > > > > The original implementation for this interrupt controller/router used > > an interrupt-map parser to determine which parent interrupts were > > present. However, this controller is not transparent, so a list of > > parent interrupts seems more appropriate, while also getting rid of the > > assumed routing to parent interrupts. > > > > Additionally, N real cascaded interrupts are implemented, instead of > > handling all input interrupts with one cascaded interrupt. Otherwise it > > is possible that the priority of the parent interrupts is not respected. > > My original question[1] still stands. An old kernel breaks with a new > DT. I am not convinced that this is an acceptable outcome. > >         M. > > [1] https://lore.kernel.org/all/874k585efy.wl-maz@kernel.org My apologies for the delay in replying, although I suppose the lack of response from others perhaps indicates that there is little interest maintaining old kernel/new DT compatibility for this hardware. John has previously argued in favour of breaking compatibility [2]. Chances of someone running a vanilla kernel build on this hardware are close to zero at this moment. The most important part, the internal ethernet switch, is only supported with out-of-tree patches. If patches can be included on an old (LTS) kernel to provide networking support, then patches can be included to be compatible with a new DT specification for the interrupts as well. OpenWrt does exactly this: use an old (5.10) kernel with new upstream features backported. The binding could be adjusted to allow (but deprecate) interrupt-map for the new two-part compatibles. This would require a new DT to both specify two-cell interrupt specifiers, and an equivalent interrupt-map definition to ensure perfect two-way compatibility. This duplicated info would need to be maintained for years however, as LTS kernels stay around for a long time. In my opinion, breaking compatibility with old kernels would allow us to move forward with a cleaner driver and binding. Best, Sander [2] https://lore.kernel.org/all/9c169aad-3c7b-2ffb-90a2-1ca791a3f411@phrozen.org/