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