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 CF2EB2DC76B; Wed, 29 Oct 2025 11:19:52 +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=1761736793; cv=none; b=VtkAXrGlWm9cW6POdJMMtrwdUirzOgXf5YGKH9Uf3VJ7E8COsGB5wbKvLOSTX3icK11FQCXoeKNBjgGluadIcWzJFYIAEvvs8e4N+Nr3Ckm3ng3+4Zwc/I90W5Mcx7zuFFMDahzolpe5udG8V/2DbMltkbKK63e6DLVVSCpM6+Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761736793; c=relaxed/simple; bh=Dh+ZcU4ASdDvqiZiGQmIVyEEV0pygfzZVWIqYkkSB78=; h=Message-ID:Date:MIME-Version:Subject:To:References:From: In-Reply-To:Content-Type; b=tHgjbwBez38MSRknNMKM1z9sL7zIzZO5SXHU3tJEminh53Ez4ImbMohIYDibbDW03YH2Mw6lwdlGIO2mFyFoQF8wTpfMTX1b1J+4iKZYG6XBjApR2SNhUqdvF28VwWzZKRW0KEOTWAXfhxIG0KuTJCaktHmV4v9dNF45upUXmbI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=B7EVqC+o; 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="B7EVqC+o" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B2D60C4CEF7; Wed, 29 Oct 2025 11:19:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1761736792; bh=Dh+ZcU4ASdDvqiZiGQmIVyEEV0pygfzZVWIqYkkSB78=; h=Date:Subject:To:References:From:In-Reply-To:From; b=B7EVqC+obkpJ9cwtEEcxn+iPMh/RHAaEh8y5xfgsskC3Un69QoGea8ahrJ7JgNUl0 vplNQl1bHY195dhxlLgNopw/mw/BVkpMHiUekW5wts4juE7MF4d7SqqhdXm1PgAQWg ik/ewch9b/0OUBhWXqOgEF1RNaWWL6rXqs0nLFn1KpMh39/YiEdzs+1HO22xmeXZOL jIb7HyhQvnE3btnI8oPRNa70rP3vRZXGWcsg9kYCUIvax4tft/71NLPdpDWsb3TkZY hiBn6TFT4IPMILYhl6c1nBp+37V6m+iy08qM7xj6O/PjKTSmlo1oMbpIPDuPfPxx/X lZs6NNNQg3krA== Message-ID: <36e2b87f-5567-4bd6-bd1b-789623441461@kernel.org> Date: Wed, 29 Oct 2025 12:19:44 +0100 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v21 2/4] dt-bindings: i2c: ast2600-i2c.yaml: Add global-regs and transfer-mode properties To: Ryan Chen , BMC-SW , "benh@kernel.crashing.org" , "joel@jms.id.au" , "andi.shyti@kernel.org" , "jk@codeconstruct.com.au" , "robh@kernel.org" , "krzk+dt@kernel.org" , "conor+dt@kernel.org" , "andrew@codeconstruct.com.au" , "p.zabel@pengutronix.de" , "andriy.shevchenko@linux.intel.com" , "naresh.solanki@9elements.com" , "linux-i2c@vger.kernel.org" , "openbmc@lists.ozlabs.org" , "devicetree@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-aspeed@lists.ozlabs.org" , "linux-kernel@vger.kernel.org" References: <20251027061240.3427875-1-ryan_chen@aspeedtech.com> <20251027061240.3427875-3-ryan_chen@aspeedtech.com> <93a2ff5f-2f8e-494b-9652-b93bc243c229@kernel.org> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 29/10/2025 10:25, Ryan Chen wrote: >> Subject: Re: [PATCH v21 2/4] dt-bindings: i2c: ast2600-i2c.yaml: Add global-regs >> and transfer-mode properties >> >> On 27/10/2025 07:12, Ryan Chen wrote: >>> The AST2600 I2C controller supports three transfer modes: byte, >>> buffer, and DMA. To allow board designers and firmware to explicitly >>> select the preferred transfer mode for each controller instance. >>> "aspeed,transfer-mode" to allow device tree to specify the desired >>> transfer method used by each I2C controller instance. >>> >>> And AST2600 i2c controller have two register mode, one is legacy >>> register layout which is mix controller/target register control >>> together, another is new mode which is separate controller/target >>> register control. >>> >> >> This implies your "reg" properties have now completely different meaning and >> this would be quite an ABI break. We discussed this probably 15 revisions ago. >> Where did you document the resolution of that discussion? > > Let me explain more about "reg" > The 'reg' property continues to describe the same register regions > (bus and buffer) as in the legacy layout. The selection between the legacy > and new register layout is controlled by a bit in the SoC-level global > register block, referenced through the new 'aspeed,global-regs' property. > Therefore, the meaning of the 'reg' property does not change and no DT ABI > break occurs. > > Should I add it in commit message about "reg" ? Then why does the address change from 0x40 to 0x80. If it is the same, it cannot change. You are describing the IO address space, total address space, as defined by datasheet. Not whatever is in the driver. Best regards, Krzysztof