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

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Message-ID: <Y7iPS48viBg0QRok@sirena.org.uk>
Date:   Fri, 6 Jan 2023 21:14:51 +0000
From:   Mark Brown <broonie@...nel.org>
To:     William Zhang <william.zhang@...adcom.com>
Cc:     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>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/16] dt-bindings: spi: Add spi peripheral specific
 property

On Fri, Jan 06, 2023 at 12:07:55PM -0800, William Zhang wrote:

> brcm,no-clk-gate is a Broadcom Broadband HS SPI controller specific
> property for certain SPI device such as Broadcom ISI voice daughtercard
> to work properly. It disables the clock gating feature when the chip
> select is deasserted for any device that wants to keep the clock
> running.

Why would this property be Broadcom specific?  Other devices could in
theory implement this.

> +properties:
> +  brcm,no-clk-gate:
> +    $ref: /schemas/types.yaml#/definitions/flag
> +    description:
> +      Some SPI device such as Broadcom ISI based voice daughtercard requires SPI
> +      clock running even when chip select is deasserted. By default the
> +      controller turns off or gate the clock when cs is not active to save
> +      power. This flag tells the controller driver to keep the clock running
> +      when chip select is not active.

This seems problematic with any host controlled chip select support...

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