Hi Rob, On 01/07/2023 07:38 AM, Rob Herring wrote:
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.On Fri, Jan 6, 2023 at 9:27 PM William Zhang <william.zhang@xxxxxxxxxxxx> wrote: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.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.
That is true but spi host controller driver reads and parses these slave device flag directly.If this is a requirement of the slave device, then the device's compatible string can imply the need for this and its driver can tell the host controller in some way.
Rob
Attachment:
smime.p7s
Description: S/MIME Cryptographic Signature
