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 38C08325491; Wed, 20 May 2026 12:16:24 +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=1779279386; cv=none; b=lQE/kY/IAB92bxPSgGidSpa1muWBrBLQUuLj5qX+MazPCy1rKpRzCCVQWYyBNH66tP1095PTyqzHlrieupaVWAoJYYMagqa2VRGT8RHUvwkrbAosMdvKqN+mThVxLR7Ar0PT5FLF5/zxQxBzuFRAm/R5pEEFyRpog3JIXDvVKIw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779279386; c=relaxed/simple; bh=hzZNz6ctMumsjHO1/78mJTATMv6hQ4TV3TrboNOqPcE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=MZhc2vYbJadD9R+AQeCPWxTuak79G+1QYtdHZWZT8HuI7ejNHjrfTBtpJA8SwJfUWpEFlevffnRfXI7UX7leeK/Fi/f4iGI9fftHvlAhfB/lFwluDt0YxUAvbaCVuVwXPIl2lTx1vEgOvZleForEsncBxmRcLbQMnYSuQqwtvGE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=VbUHxJyU; 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="VbUHxJyU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D4F691F000E9; Wed, 20 May 2026 12:16:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779279384; bh=JqTuzJtsBRIiyPsxwIfKOG4nQP71IFs5r3aLsh9ISxE=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=VbUHxJyUsFhVwT85FqHb8mMzZuIuEhYNw7QUr23Zk8Qf0tES2o82nI1mob4uHK0bu 3WhYFxkVz3LZ68RuUB46NP9gUuiJ5okzpBXe8St6IDoDE9p7OKmnNOOppQP0N0vn9T Fj7KYxmNwtql4aWPQdR+7hGZPVlvhmoW1BLz0KB4LdJPGSGy//3vBdGZBuncYH1PJo jnyWzTH8iPj+uOkW/8NAFVxQtQ/fQqRwhE3trhh8gni8Mbx7hdaMLGvToeHQSfDh8U cv7Co3NgzU1dz7iXcgtFW6vrs1nkSUxWBr55KuJ8S0LShne+jBPT1ZX2oOnDFZXUTy 4Zsw06IFIvABA== Message-ID: <14719378-7bf5-4688-81e9-bccedf618d18@kernel.org> Date: Wed, 20 May 2026 14:16:21 +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: Jisheng Zhang Cc: Mark Brown , 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> 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 13:48, Jisheng Zhang wrote: > On Wed, May 20, 2026 at 09:09:55AM +0200, Krzysztof Kozlowski wrote: >> On 20/05/2026 01:38, Jisheng Zhang wrote: >>> On Fri, May 15, 2026 at 10:00:50AM +0200, Krzysztof Kozlowski wrote: >>>> On Mon, May 11, 2026 at 11:17:31AM +0800, Jisheng Zhang wrote: >>>>> The cdns xspi controller SDMA data port may support wider I/O width. >>>>> Wider I/O width can benefit performance. A simple test with QSPI nor >>>>> flash on one arm64 platform: >>>>> >>>>> 1 byte io width (default): >>>>> # dd if=/dev/mtdblock0 of=/dev/null bs=8192 count=1000 >>>>> 1000+0 records in >>>>> 1000+0 records out >>>>> 8192000 bytes (7.8MB) copied, 1.368735 seconds, 5.7MB/s >>>>> >>>>> 4 bytes io width: >>>>> # dd if=/dev/mtdblock0 of=/dev/null bs=8192 count=1000 >>>>> 1000+0 records in >>>>> 1000+0 records out >>>>> 8192000 bytes (7.8MB) copied, 1.088787 seconds, 7.2MB/s >>>>> >>>>> Improved by 26.3%! >>>>> >>>>> Add dt binding for sdma-io-width. >>>>> >>>>> Signed-off-by: Jisheng Zhang >>>>> --- >>>>> Documentation/devicetree/bindings/spi/cdns,xspi.yaml | 6 ++++++ >>>>> 1 file changed, 6 insertions(+) >>>>> >>>>> diff --git a/Documentation/devicetree/bindings/spi/cdns,xspi.yaml b/Documentation/devicetree/bindings/spi/cdns,xspi.yaml >>>>> index 38a5795589de..1fd4b6dfd417 100644 >>>>> --- a/Documentation/devicetree/bindings/spi/cdns,xspi.yaml >>>>> +++ b/Documentation/devicetree/bindings/spi/cdns,xspi.yaml >>>>> @@ -40,6 +40,12 @@ properties: >>>>> interrupts: >>>>> maxItems: 1 >>>>> >>>>> + sdma-io-width: >>>>> + description: Slave DMA data port I/O width (in bytes) >>>> >>>> Waht is SDMA? What is Slave DMA? The same? >>>> >>>> Why this cannot be deduced from the compatible? DMA is fixed per >>>> platform and SDMA do not sound like SPI device (so slave in older >>>> terminology) property. >>> >>> in cdns xspi, sdma == slave dma. It can be read by any master, such >>> as DMA engine or CPU. Its purpose and usage is similar as the data >>> reg in other spi controllers, e.g the DW_SPI_DR in dw spi. >> >> You did not really answer the questions. >> > > 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? 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. Argument that some drivers do that is obviously wrong, so I am jumping there. Best regards, Krzysztof