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From: Vinod Koul <vkoul@kernel.org>
To: Eugen.Hristev@microchip.com
Cc: robh@kernel.org, Tudor.Ambarus@microchip.com,
	Ludovic.Desroches@microchip.com, dmaengine@vger.kernel.org,
	devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, Nicolas.Ferre@microchip.com
Subject: Re: [PATCH 6/7] dt-bindings: dmaengine: at_xdmac: add optional microchip,m2m property
Date: Fri, 16 Oct 2020 12:36:18 +0530	[thread overview]
Message-ID: <20201016070618.GW2968@vkoul-mobl> (raw)
In-Reply-To: <6f305564-e91c-794b-0025-de805f1d1a58@microchip.com>

Hi Eugen,

On 16-10-20, 06:45, Eugen.Hristev@microchip.com wrote:
> On 23.09.2020 02:33, Rob Herring wrote:
> 
> > On Mon, Sep 14, 2020 at 05:09:55PM +0300, Eugen Hristev wrote:
> >> Add optional microchip,m2m property that specifies if a controller is
> >> dedicated to memory to memory operations only.
> >>
> >> Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
> >> ---
> >>   Documentation/devicetree/bindings/dma/atmel-xdma.txt | 6 ++++++
> >>   1 file changed, 6 insertions(+)
> >>
> >> diff --git a/Documentation/devicetree/bindings/dma/atmel-xdma.txt b/Documentation/devicetree/bindings/dma/atmel-xdma.txt
> >> index 510b7f25ba24..642da6b95a29 100644
> >> --- a/Documentation/devicetree/bindings/dma/atmel-xdma.txt
> >> +++ b/Documentation/devicetree/bindings/dma/atmel-xdma.txt
> >> @@ -15,6 +15,12 @@ the dmas property of client devices.
> >>       interface identifier,
> >>       - bit 30-24: PERID, peripheral identifier.
> >>
> >> +Optional properties:
> >> +- microchip,m2m: this controller is connected on AXI only to memory and it's
> >> +     dedicated to memory to memory DMA operations. If this option is
> >> +     missing, it's assumed that the DMA controller is connected to
> >> +     peripherals, thus it's a per2mem and mem2per.
> > 
> > Wouldn't 'dma-requests = <0>' cover this case?
> > 
> > Rob
> > 
> 
> Hi Rob,
> 
> I do not think so. With requests = 0, it means that actually the DMA 
> controller is unusable ?
> Since you suggest requests = 0, it means that it cannot take requests at 
> all ?
> I do not find another example in current DT with this property set to zero.

Not really, dma-requests implies "request signals supported" which are
used for peripheral cases. m2m does not need request signals, so it is
very reasonable to conclude that dma-requests = <0> would imply no
peripheral support and only m2m support.

Thanks
-- 
~Vinod

WARNING: multiple messages have this Message-ID (diff)
From: Vinod Koul <vkoul@kernel.org>
To: Eugen.Hristev@microchip.com
Cc: robh@kernel.org, devicetree@vger.kernel.org,
	Tudor.Ambarus@microchip.com, linux-kernel@vger.kernel.org,
	Ludovic.Desroches@microchip.com, dmaengine@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 6/7] dt-bindings: dmaengine: at_xdmac: add optional microchip,m2m property
Date: Fri, 16 Oct 2020 12:36:18 +0530	[thread overview]
Message-ID: <20201016070618.GW2968@vkoul-mobl> (raw)
In-Reply-To: <6f305564-e91c-794b-0025-de805f1d1a58@microchip.com>

Hi Eugen,

On 16-10-20, 06:45, Eugen.Hristev@microchip.com wrote:
> On 23.09.2020 02:33, Rob Herring wrote:
> 
> > On Mon, Sep 14, 2020 at 05:09:55PM +0300, Eugen Hristev wrote:
> >> Add optional microchip,m2m property that specifies if a controller is
> >> dedicated to memory to memory operations only.
> >>
> >> Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
> >> ---
> >>   Documentation/devicetree/bindings/dma/atmel-xdma.txt | 6 ++++++
> >>   1 file changed, 6 insertions(+)
> >>
> >> diff --git a/Documentation/devicetree/bindings/dma/atmel-xdma.txt b/Documentation/devicetree/bindings/dma/atmel-xdma.txt
> >> index 510b7f25ba24..642da6b95a29 100644
> >> --- a/Documentation/devicetree/bindings/dma/atmel-xdma.txt
> >> +++ b/Documentation/devicetree/bindings/dma/atmel-xdma.txt
> >> @@ -15,6 +15,12 @@ the dmas property of client devices.
> >>       interface identifier,
> >>       - bit 30-24: PERID, peripheral identifier.
> >>
> >> +Optional properties:
> >> +- microchip,m2m: this controller is connected on AXI only to memory and it's
> >> +     dedicated to memory to memory DMA operations. If this option is
> >> +     missing, it's assumed that the DMA controller is connected to
> >> +     peripherals, thus it's a per2mem and mem2per.
> > 
> > Wouldn't 'dma-requests = <0>' cover this case?
> > 
> > Rob
> > 
> 
> Hi Rob,
> 
> I do not think so. With requests = 0, it means that actually the DMA 
> controller is unusable ?
> Since you suggest requests = 0, it means that it cannot take requests at 
> all ?
> I do not find another example in current DT with this property set to zero.

Not really, dma-requests implies "request signals supported" which are
used for peripheral cases. m2m does not need request signals, so it is
very reasonable to conclude that dma-requests = <0> would imply no
peripheral support and only m2m support.

Thanks
-- 
~Vinod

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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2020-10-16  7:06 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-14 14:09 [PATCH 0/7] dmaengine: add support for sama7g5 based at_xdmac Eugen Hristev
2020-09-14 14:09 ` Eugen Hristev
2020-09-14 14:09 ` [PATCH 1/7] dmaengine: at_xdmac: separate register defines into header file Eugen Hristev
2020-09-14 14:09   ` Eugen Hristev
2020-09-23  5:07   ` Tudor.Ambarus
2020-09-23  5:07     ` Tudor.Ambarus
2020-09-14 14:09 ` [PATCH 2/7] MAINTAINERS: add dma/at_xdmac_regs.h to XDMAC driver entry Eugen Hristev
2020-09-14 14:09   ` Eugen Hristev
2020-09-23  5:12   ` Tudor.Ambarus
2020-09-23  5:12     ` Tudor.Ambarus
2020-09-14 14:09 ` [PATCH 3/7] dt-bindings: dmaengine: at_xdmac: add compatible with microchip,sama7g5 Eugen Hristev
2020-09-14 14:09   ` [PATCH 3/7] dt-bindings: dmaengine: at_xdmac: add compatible with microchip, sama7g5 Eugen Hristev
2020-09-22 23:32   ` [PATCH 3/7] dt-bindings: dmaengine: at_xdmac: add compatible with microchip,sama7g5 Rob Herring
2020-09-22 23:32     ` Rob Herring
2020-09-14 14:09 ` [PATCH 4/7] dmaengine: at_xdmac: adapt perid for mem2mem operations Eugen Hristev
2020-09-14 14:09   ` Eugen Hristev
2020-09-23  5:30   ` Tudor.Ambarus
2020-09-23  5:30     ` Tudor.Ambarus
2020-09-23  5:35     ` Tudor.Ambarus
2020-09-23  5:35       ` Tudor.Ambarus
2020-09-14 14:09 ` [PATCH 5/7] dmaengine: at_xdmac: add support for sama7g5 based at_xdmac Eugen Hristev
2020-09-14 14:09   ` Eugen Hristev
2020-09-23  7:08   ` Tudor.Ambarus
2020-09-23  7:08     ` Tudor.Ambarus
2020-10-16  6:52     ` Eugen.Hristev
2020-10-16  6:52       ` Eugen.Hristev
2020-09-14 14:09 ` [PATCH 6/7] dt-bindings: dmaengine: at_xdmac: add optional microchip,m2m property Eugen Hristev
2020-09-14 14:09   ` [PATCH 6/7] dt-bindings: dmaengine: at_xdmac: add optional microchip, m2m property Eugen Hristev
2020-09-22 23:33   ` [PATCH 6/7] dt-bindings: dmaengine: at_xdmac: add optional microchip,m2m property Rob Herring
2020-09-22 23:33     ` Rob Herring
2020-10-16  6:45     ` Eugen.Hristev
2020-10-16  6:45       ` Eugen.Hristev
2020-10-16  7:06       ` Vinod Koul [this message]
2020-10-16  7:06         ` Vinod Koul
2020-10-16  7:09         ` Eugen.Hristev
2020-10-16  7:09           ` Eugen.Hristev
2020-09-14 14:09 ` [PATCH 7/7] dmaengine: at_xdmac: add AXI priority support and recommended settings Eugen Hristev
2020-09-14 14:09   ` Eugen Hristev

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