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 8578819CD04; Tue, 27 Aug 2024 09:29:21 +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=1724750961; cv=none; b=BnaLN2uLqiT4aMoBK1YMJpelJMJNk8fLAeoN+OQ8uVJ3w6CtcJ6VH0IyPdp7itJHEwiyahSU8QNF7gUZAGR/75SxDLiNZLhAjWsQzsdnF/65fXpK29SetK3PLDd3ciuugRcppM1+C0c8GStdc7RpUeV8M94+3Fw1bUKS2t22rIg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724750961; c=relaxed/simple; bh=29eZ04A38P++EWcPkRYyViQabv96Sj5ogaunSTwwY0Y=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=YW7LIAd6bJh81mqF3T32/sng3SgdLjBcuzeDlo5HOT86m2Sqi4PamzLkfeORnBqcMc0RRMz7nS7xL0z4BPUJqUiwZ0as4EAlqiXB01hCGFFnSo/24E4wlbgWVmy9/4CUZYlxvqcHHsbo/RtfxC88OyJehoh7EUy6a9WrpmQ+7bY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=eoFAryyI; 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="eoFAryyI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4C823C8B7B4; Tue, 27 Aug 2024 09:29:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1724750961; bh=29eZ04A38P++EWcPkRYyViQabv96Sj5ogaunSTwwY0Y=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=eoFAryyIhdZKWCjqEbgAKcqd7M5ffg1f0nDQHKe1joCgk/RNbP9Ji3Tiad/QD1f72 0t8LqbwL/WQ6ykfyYLCT3ytOJEaqlsLIjUwOisxU3CrkgXr8zKfDezokE8Xh0bt7Lo 2dJQ3GzChfRdoQ1IEtKPWMleooiKzoE4CF4LFkFKlMbyEszm0zpo6BpQNcAIpSiTc9 U2UruzaO+Ypnro5tmw8LwRcbu3Cu/yV/PSssVl7NhgXi9qy8q032CPZ7/BTSH6EoP0 dUsBsPTb5ChTo7uv1iZMpjtrByIHHg58Xk3bmPGsjwO8gx2+yuHLHkTE21e9hMO8yg 7h6KgQ6IQz9jw== Message-ID: <0ca0fc20-421e-4bbc-bcda-9e5c2ea3b1b4@kernel.org> Date: Tue, 27 Aug 2024 11:29:15 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 3/6] dt-bindings: PCI: ti,am65: Extend for use with PVU To: Jan Kiszka Cc: Nishanth Menon , Santosh Shilimkar , Vignesh Raghavendra , Rob Herring , Krzysztof Kozlowski , Conor Dooley , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, Siddharth Vadapalli , Bao Cheng Su , Hua Qian Li , Diogo Ivo References: <82ac9e266f6aca42699ec4a3c8f10887789ee6bf.1724709007.git.jan.kiszka@siemens.com> <6c28d580-9961-4bac-adcd-1724de68c9fb@siemens.com> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 27/08/2024 11:22, Jan Kiszka wrote: > On 27.08.24 08:37, Krzysztof Kozlowski wrote: >> On Mon, Aug 26, 2024 at 11:50:04PM +0200, Jan Kiszka wrote: >>> From: Jan Kiszka >>> >>> Describe also the VMAP registers which are needed in order to make use >>> of the PVU with this PCI host. Furthermore, permit to specify a >>> restricted DMA pool by phandle. >> >> That's an ABI break without explanation why it is necessary. >> > > It is needed in order to support the PVU, as written above. Above say only that you want a new feature and that's not really suitable explanation for ABI break, because answer to this is: add new feature without breaking existing users. But maybe there is a bug or something does not work or never work or there are no users, don't know. > > Previous versions of this binding likely didn't consider this use case > and therefore didn't describe all registers associated with the hardware. > > BTW, if you see a way to add the required registers without breaking > more than needed, I'm all ears. At least the kernel driver will continue > to work with older DTs when you disable PVU support or do not add a DMA > pool to the DT. If there is no ABI break, because driver still handles correctly old DTB, then mention it in the commit msg. Best regards, Krzysztof