From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 A78EE175A6B; Wed, 20 May 2026 13:22:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779283331; cv=none; b=lVFpQ8PIRsILnpWCA4FVAgmBNDcGvLbL+TE4R3b0HnKGuXWJVorwY5G/mSGRdKINdC14hPGJtamAPLjsG7Qev0TinylnIBaNSUj/tBKwiZO9QtjwVLdQAab4ng3HvfEt8EaYuMbXnPh3e55esEdNoLO5BYCjDhitlc9YtRGhK+c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779283331; c=relaxed/simple; bh=doX3RJ2hmfJxJhpYJ4HSxaM4I1v5ciwLznCt4uw1A+M=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=RFUaNdNFJ5O/kNxAUFdfByHt0UzUsPTfTBx9bBz45Q6soAn1Id2aCIpTNv1eQ8HIlpMzpkPPBIMEthLWSDcSvslDXGLpT5a9B4buWpe8QPRhd9iTbUkiAgapY7unWMKHZLG3T0kz0ORGNrRFWDr0ZW2AVTFPqZLN2ioFxzu8YEM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dPYbOolY; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="dPYbOolY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7C0081F000E9; Wed, 20 May 2026 13:22:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779283330; bh=M1zv1TE3ixI3RchqcaQ5nesDMV9sADtAmDYYuFd10Sc=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=dPYbOolYrOtkLVYqCO+TFbvwawOVHHFbzFza5wGxKZMrc7gN5wewgI60c6xcovxnl 9FtTxXfde0/StDN2/cXQzKr9F3DX68/ADOIxKT0E+tPZcKV8yYl0QQubcA3i5Dv86w 10izAcNla1Zaf+kSFd1mhBedztwtDzFEZaQAuHNUYKekM66ZMQzTqlmbRAmuz5B0Q2 u1sKxzjPG5F98sjo/hxSbsdiw0J2n391BYsdtw7m9v/QQdUm0CNfT6n9ozqaqGNTsL wr0mGVo5a9zf9un1e4PkIdR61tnCIY/YoIXk+VFDvRkYLPcm9e8lKTcLTlLaBWV6pq BkQGtB3pTHKKQ== Message-ID: <37a3e9dd-88c2-4d8d-8ae4-6037a1eeedcc@kernel.org> Date: Wed, 20 May 2026 15:22:07 +0200 Precedence: bulk X-Mailing-List: linux-spi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] spi: dt-bindings: cdns,xspi: add sdma-io-width To: Mark Brown Cc: Jisheng Zhang , Rob Herring , Krzysztof Kozlowski , Conor Dooley , linux-spi@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260511031732.3199-1-jszhang@kernel.org> <20260511031732.3199-2-jszhang@kernel.org> <20260515-expert-devious-cricket-faff56@quoll> <21d30826-bfe6-44cd-8c89-c1986f539e48@kernel.org> <14719378-7bf5-4688-81e9-bccedf618d18@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 20/05/2026 14:30, Mark Brown wrote: > On Wed, May 20, 2026 at 02:16:21PM +0200, Krzysztof Kozlowski wrote: >> On 20/05/2026 13:48, Jisheng Zhang wrote: > >>> If you mean "Why this cannot be deduced from the compatible?", I think >>> the slave dma port is part of the cdns xspi, so its io width belongs >>> to xSPI device property. >>> From another side, we have seen such property in other drivers such as >>> the reg-io-width for the dw spi DW_SPI_DR port io width. > >> So you mean it depends on SPI device? Then why spi-peripheral-props is >> not applicable here? > > That will be controller side, not device side. > >> If this is not bus width, but DMA-something, is not really then SPI >> device dependent, but rather DMA controller limitation, so either >> deducible from compatible or something else is missing here. > > My understanding is that this is a connection between the SPI and DMA > controllers so it's not as obvious as it could be which side of that > link should have the property, eg: > > https://www.cadence.com/content/dam/cadence-www/global/en_US/documents/tools/silicon-solutions/design-ip/controller-ip-qspi.pdf > > shows a separate direct connection between the DMA controller and the > xSPI controller, the DMA controller isn't interacting with registers on > the CPU visible buses. The width is probably a design time configurable > option on both sides of the link. Yes and that sounds a lot specific to particular controller, thus should be implied by / deducible from the compatible. Best regards, Krzysztof