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 [thread overview]
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
next prev parent reply other threads:[~2019-09-13 14:36 UTC|newest]
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
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