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SubjectRe: [PATCH 03/16] dt-bindings: spi: Add spi peripheral specific property
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Hi Mark,

On 01/06/2023 01:14 PM, Mark Brown wrote:
> 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.
>
It does not need to be Broadcom specific if other SoC's SPI bus
controller support such function. I am not aware of such case but
certainly I am no expert on other chips. I can put it in the generic
spi-peripheral-props.yaml if that is what you suggest.

>> +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...
>
Yes those ISI chip based voice cards do need such strange requirement
and will not work with other controller. That is one of the reason I
put this as Broadcom specific option.
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