Re: [RFC PATCH net-next 1/4] dt-bindings: dmaengine: bam_dma: Add remote power collapse mode

From: Rob Herring <robh@kernel.org>
To: Stephan Gerhold <stephan@gerhold.net>
Cc: "David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Loic Poulain <loic.poulain@linaro.org>,
	Sergey Ryazanov <ryazanov.s.a@gmail.com>,
	Johannes Berg <johannes@sipsolutions.net>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Andy Gross <agross@kernel.org>, Vinod Koul <vkoul@kernel.org>,
	Aleksander Morgado <aleksander@aleksander.es>,
	netdev@vger.kernel.org, linux-arm-msm@vger.kernel.org,
	dmaengine@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, phone-devel@vger.kernel.org,
	~postmarketos/upstreaming@lists.sr.ht,
	Jeffrey Hugo <jeffrey.l.hugo@gmail.com>
Subject: Re: [RFC PATCH net-next 1/4] dt-bindings: dmaengine: bam_dma: Add remote power collapse mode
Date: Thu, 29 Jul 2021 13:36:31 -0600	[thread overview]
Message-ID: <YQMDP6+ft/iRJQQr@robh.at.kernel.org> (raw)
In-Reply-To: <20210719145317.79692-2-stephan@gerhold.net>

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@gerhold.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