dmaengine Archive on lore.kernel.org
 help / color / Atom feed
From: Rob Herring <robh@kernel.org>
To: Peter Ujfalusi <peter.ujfalusi@ti.com>
Cc: vkoul@kernel.org, dmaengine@vger.kernel.org,
	linux-kernel@vger.kernel.org, dan.j.williams@intel.com,
	devicetree@vger.kernel.org
Subject: Re: [PATCH 1/3] dt-bindings: dma: Add documentation for DMA domains
Date: Fri, 13 Sep 2019 15:36:28 +0100
Message-ID: <5d7ba96c.1c69fb81.ee467.32b9@mx.google.com> (raw)
In-Reply-To: <20190910115037.23539-2-peter.ujfalusi@ti.com>

On Tue, Sep 10, 2019 at 02:50:35PM +0300, Peter Ujfalusi wrote:
> On systems where multiple DMA controllers available, non Slave (for example
> memcpy operation) users can not be described in DT as there is no device
> involved from the DMA controller's point of view, DMA binding is not usable.
> However in these systems still a peripheral might need to be serviced by or
> it is better to serviced by specific DMA controller.
> When a memcpy is used to/from a memory mapped region for example a DMA in the
> same domain can perform better.
> For generic software modules doing mem 2 mem operations it also matter that
> they will get a channel from a controller which is faster in DDR to DDR mode
> rather then from the first controller happen to be loaded.
> 
> This property is inherited, so it may be specified in a device node or in any
> of its parent nodes.

If a device needs mem2mem dma, I think we should just use the existing 
dma binding. The provider will need a way to define cell values which 
mean mem2mem.

For generic s/w, it should be able to query the dma speed or get a 
preferred one IMO. It's not a DT problem.

We measure memcpy speeds at boot time to select the fastest 
implementation for a chip, why not do that for mem2mem DMA?

> 
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
> ---
>  .../devicetree/bindings/dma/dma-domain.yaml   | 88 +++++++++++++++++++
>  1 file changed, 88 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/dma/dma-domain.yaml

Note that you have several errors in your schema. Run 'make dt_bindings_check'.

Rob


  reply index

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-10 11:50 [PATCH 0/3] dmaengine: Support for DMA domain controllers Peter Ujfalusi
2019-09-10 11:50 ` [PATCH 1/3] dt-bindings: dma: Add documentation for DMA domains Peter Ujfalusi
2019-09-13 14:36   ` Rob Herring [this message]
2019-09-16 11:21     ` Peter Ujfalusi
2019-09-24 13:56       ` Peter Ujfalusi
2019-09-24 14:44       ` Rob Herring
2019-10-04 15:56         ` Peter Ujfalusi
2019-09-10 11:50 ` [PATCH 2/3] dmaengine: of_dma: Function to look up the DMA domain of a client Peter Ujfalusi
2019-09-10 11:50 ` [PATCH 3/3] dmaengine: Support for requesting channels preferring DMA domain controller Peter Ujfalusi

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=5d7ba96c.1c69fb81.ee467.32b9@mx.google.com \
    --to=robh@kernel.org \
    --cc=dan.j.williams@intel.com \
    --cc=devicetree@vger.kernel.org \
    --cc=dmaengine@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=peter.ujfalusi@ti.com \
    --cc=vkoul@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

dmaengine Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/dmaengine/0 dmaengine/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 dmaengine dmaengine/ https://lore.kernel.org/dmaengine \
		dmaengine@vger.kernel.org dmaengine@archiver.kernel.org
	public-inbox-index dmaengine

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.dmaengine


AGPL code for this site: git clone https://public-inbox.org/ public-inbox