netdev - Re: [RFC PATCH net-next 1/4] dt-bindings: dmaengine: bam

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Message-ID: <YQMDP6+ft/iRJQQr@robh.at.kernel.org>
Date:   Thu, 29 Jul 2021 13:36:31 -0600
From:   Rob Herring <robh@...nel.org>
To:     Stephan Gerhold <stephan@...hold.net>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Loic Poulain <loic.poulain@...aro.org>,
        Sergey Ryazanov <ryazanov.s.a@...il.com>,
        Johannes Berg <johannes@...solutions.net>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Andy Gross <agross@...nel.org>, Vinod Koul <vkoul@...nel.org>,
        Aleksander Morgado <aleksander@...ksander.es>,
        netdev@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        dmaengine@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, phone-devel@...r.kernel.org,
        ~postmarketos/upstreaming@...ts.sr.ht,
        Jeffrey Hugo <jeffrey.l.hugo@...il.com>
Subject: Re: [RFC PATCH net-next 1/4] dt-bindings: dmaengine: bam_dma: Add
 remote power collapse mode

On Mon, Jul 19, 2021 at 04:53:14PM +0200, Stephan Gerhold wrote:
> In some configurations, the BAM DMA controller is set up by a remote
> processor and the local processor can simply start making use of it
> without setting up the BAM. This is already supported using the
> "qcom,controlled-remotely" property.
> 
> However, for some reason another possible configuration is that the
> remote processor is responsible for powering up the BAM, but we are
> still responsible for initializing it (e.g. resetting it etc). Add
> a "qcom,remote-power-collapse" property to describe that configuration.
> 
> Signed-off-by: Stephan Gerhold <stephan@...hold.net>
> ---
> NOTE: This is *not* a compile-time requirement for the BAM-DMUX driver
>       so this could also go through the dmaengine tree.
> 
> Also note that there is an ongoing effort to convert these bindings
> to DT schema but sadly there were not any updates for a while. :/
> https://lore.kernel.org/linux-arm-msm/20210519143700.27392-2-bhupesh.sharma@linaro.org/
> ---
>  Documentation/devicetree/bindings/dma/qcom_bam_dma.txt | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/dma/qcom_bam_dma.txt b/Documentation/devicetree/bindings/dma/qcom_bam_dma.txt
> index cf5b9e44432c..362a4f0905a8 100644
> --- a/Documentation/devicetree/bindings/dma/qcom_bam_dma.txt
> +++ b/Documentation/devicetree/bindings/dma/qcom_bam_dma.txt
> @@ -15,6 +15,8 @@ Required properties:
>    the secure world.
>  - qcom,controlled-remotely : optional, indicates that the bam is controlled by
>    remote proccessor i.e. execution environment.
> +- qcom,remote-power-collapse : optional, indicates that the bam is powered up by
> +  a remote processor but must be initialized by the local processor.

Wouldn't 'qcom,remote-power' or 'qcom,remote-powered' be sufficient? I 
don't understand what 'collapse' means here. Doesn't sound good though.

Rob