linux-kernel - Re: [PATCH 03/16] dt-bindings: spi: Add spi peripheral specific property

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Message-ID: <Y7xosoZMJEwRi1ok@sirena.org.uk>
Date:   Mon, 9 Jan 2023 19:19:14 +0000
From:   Mark Brown <broonie@...nel.org>
To:     William Zhang <william.zhang@...adcom.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Linux SPI List <linux-spi@...r.kernel.org>,
        Broadcom Kernel List <bcm-kernel-feedback-list@...adcom.com>,
        anand.gore@...adcom.com, tomer.yacoby@...adcom.com,
        dan.beygelman@...adcom.com, joel.peshkin@...adcom.com,
        f.fainelli@...il.com, jonas.gorski@...il.com,
        kursad.oney@...adcom.com, dregan@...l.com,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/16] dt-bindings: spi: Add spi peripheral specific
 property

On Mon, Jan 09, 2023 at 12:06:13AM -0800, William Zhang wrote:
> > On Fri, Jan 6, 2023 at 9:27 PM William Zhang <william.zhang@...adcom.com> wrote:

> > Keeping the clock on or not would affect all devices unless you have a
> > per device clock you can gate, so making this a per device flag
> > doesn't make sense.

> This applies only to each chip select. There is only one device under each
> chip select.  So won't impact any other devices under other cs.

I don't understand how this would work - usually a SPI controller has a
single set of clock, MOSI and MISO lines with the only per device thing
being the chip select.  If the clock line is used by all devices then it
must be kept on for all of them if it's to be kept on for one of them.

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