linux-kernel - Re: [PATCH v7 1/8] dmaengine: add DMA_PREP_LOCK and DMA_PREP

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Message-ID: <Z+lvYUeAElcW5uNl@vaman>
Date: Sun, 30 Mar 2025 21:50:49 +0530
From: Vinod Koul <vkoul@...nel.org>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Thara Gopinath <thara.gopinath@...il.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	"David S. Miller" <davem@...emloft.net>,
	Jonathan Corbet <corbet@....net>,
	Md Sadre Alam <quic_mdalam@...cinc.com>,
	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
	linux-crypto@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	linux-kernel@...r.kernel.org, dmaengine@...r.kernel.org,
	linux-doc@...r.kernel.org,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v7 1/8] dmaengine: add DMA_PREP_LOCK and DMA_PREP_UNLOCK
 flag

On 11-03-25, 10:25, Bartosz Golaszewski wrote:
> From: Md Sadre Alam <quic_mdalam@...cinc.com>
> 
> Add lock and unlock flags for the command descriptor. With the former set
> in the requester pipe, the bam controller will lock all other pipes and
> process the request only from requester pipe. Unlocking can only be
> performed from the same pipe.
> 
> Setting the DMA_PREP_LOCK/DMA_PREP_UNLOCK flags in the command
> descriptor means, the caller requests the BAM controller to be locked
> for the duration of the transaction. In this case the BAM driver must
> set the LOCK/UNLOCK bits in the HW descriptor respectively.
> 
> Only BAM IPs version 1.4.0 and above support the LOCK/UNLOCK feature.
> 
> Signed-off-by: Md Sadre Alam <quic_mdalam@...cinc.com>
> [Bartosz: reworked the commit message]
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> ---
>  Documentation/driver-api/dmaengine/provider.rst | 15 +++++++++++++++
>  include/linux/dmaengine.h                       |  6 ++++++
>  2 files changed, 21 insertions(+)
> 
> diff --git a/Documentation/driver-api/dmaengine/provider.rst b/Documentation/driver-api/dmaengine/provider.rst
> index 3085f8b460fa..a032e55d0a4f 100644
> --- a/Documentation/driver-api/dmaengine/provider.rst
> +++ b/Documentation/driver-api/dmaengine/provider.rst
> @@ -628,6 +628,21 @@ DMA_CTRL_REUSE
>    - This flag is only supported if the channel reports the DMA_LOAD_EOT
>      capability.
>  
> +- DMA_PREP_LOCK
> +
> +  - If set, the DMA will lock all other pipes not related to the current
> +    pipe group, and keep handling the current pipe only.
> +
> +  - All pipes not within this group will be locked by this pipe upon lock
> +    event.
> +
> +  - only pipes which are in the same group and relate to the same Environment
> +    Execution(EE) will not be locked by a certain pipe.

This does not make sense for me in generic context... Pipes and EEs are
implementation details... Please generalise the description for a
dma controller...

-- 
~Vinod