linux-kernel - Re: [PATCH V1 19/26] DT bindings: spi: add spi client device properties

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Date:   Mon, 1 Apr 2019 14:37:23 +0700
From:   Mark Brown <broonie@...nel.org>
To:     Sowjanya Komatineni <skomatineni@...dia.com>
Cc:     thierry.reding@...il.com, jonathanh@...dia.com, talho@...dia.com,
        robh+dt@...nel.org, mark.rutland@....com, kyarlagadda@...dia.com,
        ldewangan@...dia.com, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-spi@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH V1 19/26] DT bindings: spi: add spi client device
 properties

On Tue, Mar 26, 2019 at 10:56:40PM -0700, Sowjanya Komatineni wrote:
> This patch adds below cs timing properties to allow SPI master configuring
> setup, hold and time interval between two SPI transactions to meet specific
> SPI client device requirements.
>  CS setup time
>  CS hold time
>  CS inactive delay
> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1;
> 	t=1553666253; bh=TbJVgRAIkjok3TkKNkfcvYc4WGyZhOpiH6sUZvadGrQ=;
> 	h=X-PGP-Universal:From:To:CC:Subject:Date:Message-ID:X-Mailer:
> 	 In-Reply-To:References:X-NVConfidentiality:MIME-Version:
> 	 Content-Type;
> 	b=Tud9guY5XCzkjKA2k2n0+xO/vTfMTNhH1e0viAyYmlgoG/j+uSBAAmOeZucVUlmEa
> 	 rwqxlSm+rkYMUfgSWqmJXqEjgRIAqMhA32FOJmhgpblGwYUR22hnbdhbk4TcqMNsIO

Something got corrupted?

> +spi-client device controller properties:
> +- nvidia,cs-setup-clk-count: CS setup timing parameter.
> +- nvidia,cs-hold-clk-count: CS hold timing parameter.
> +- nvidia,cs-inactive-cycles: CS inactive delay in terms of clock between
> +  transfers.

Why are these being done as nVidia specific properties rather than
generic ones and why are these being configured in DT rather than by the
client driver?  If the devices have particular timing requirements for
chip select presumably that's going to apply no matter what controller
or system they're used with so it seems best to configure this in the
client driver and have an API that any controller can implement.

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