[v2,1/5] dt-bindings: iio: at91-sama5d2_adc: add optional dma property

Message ID 1507703732-29175-2-git-send-email-eugen.hristev@microchip.com
State Not Applicable
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Series
  • iio: adc: at91-sama5d2_adc: add DMA support
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Commit Message

Eugen Hristev Oct. 11, 2017, 6:35 a.m.
Added property for DMA configuration of the device.

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
---
 Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt | 7 +++++++
 1 file changed, 7 insertions(+)

Comments

Rob Herring Oct. 13, 2017, 9:51 p.m. | #1
On Wed, Oct 11, 2017 at 09:35:28AM +0300, Eugen Hristev wrote:
> Added property for DMA configuration of the device.
> 
> Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
> ---
>  Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt b/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt
> index 552e7a8..5f94d479 100644
> --- a/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt
> +++ b/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt
> @@ -17,6 +17,11 @@ Required properties:
>    This property uses the IRQ edge types values: IRQ_TYPE_EDGE_RISING ,
>    IRQ_TYPE_EDGE_FALLING or IRQ_TYPE_EDGE_BOTH
>  
> +Optional properties:
> +  - dmas: Phandle to dma channel for the ADC.
> +  See ../../dma/dma.txt for details.
> +  - dma-names: Must be "rx" when dmas property is being used.

-names is pointless when there is only one.

Otherwise,

Acked-by: Rob Herring <robh@kernel.org>
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Alexandre Belloni Oct. 19, 2017, 11:14 a.m. | #2
On 13/10/2017 at 16:51:42 -0500, Rob Herring wrote:
> On Wed, Oct 11, 2017 at 09:35:28AM +0300, Eugen Hristev wrote:
> > Added property for DMA configuration of the device.
> > 
> > Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
> > ---
> >  Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt b/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt
> > index 552e7a8..5f94d479 100644
> > --- a/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt
> > +++ b/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt
> > @@ -17,6 +17,11 @@ Required properties:
> >    This property uses the IRQ edge types values: IRQ_TYPE_EDGE_RISING ,
> >    IRQ_TYPE_EDGE_FALLING or IRQ_TYPE_EDGE_BOTH
> >  
> > +Optional properties:
> > +  - dmas: Phandle to dma channel for the ADC.
> > +  See ../../dma/dma.txt for details.
> > +  - dma-names: Must be "rx" when dmas property is being used.
> 
> -names is pointless when there is only one.
> 

You didn't reply to the question I had previously about that: What if at
some point, we have multiple dmas in the same binding?
Rob Herring Oct. 19, 2017, 9:58 p.m. | #3
On Thu, Oct 19, 2017 at 6:14 AM, Alexandre Belloni
<alexandre.belloni@free-electrons.com> wrote:
> On 13/10/2017 at 16:51:42 -0500, Rob Herring wrote:
>> On Wed, Oct 11, 2017 at 09:35:28AM +0300, Eugen Hristev wrote:
>> > Added property for DMA configuration of the device.
>> >
>> > Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
>> > ---
>> >  Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt | 7 +++++++
>> >  1 file changed, 7 insertions(+)
>> >
>> > diff --git a/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt b/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt
>> > index 552e7a8..5f94d479 100644
>> > --- a/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt
>> > +++ b/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt
>> > @@ -17,6 +17,11 @@ Required properties:
>> >    This property uses the IRQ edge types values: IRQ_TYPE_EDGE_RISING ,
>> >    IRQ_TYPE_EDGE_FALLING or IRQ_TYPE_EDGE_BOTH
>> >
>> > +Optional properties:
>> > +  - dmas: Phandle to dma channel for the ADC.
>> > +  See ../../dma/dma.txt for details.
>> > +  - dma-names: Must be "rx" when dmas property is being used.
>>
>> -names is pointless when there is only one.
>>
>
> You didn't reply to the question I had previously about that: What if at
> some point, we have multiple dmas in the same binding?

Then add dma-names at that point and rx has to be first. If you know
there's other channels, then add them now. Don't evolve the bindings
needlessly based on what a driver supports.

Would another channel make sense here? Maybe multi-channel rx in which
case your naming wouldn't be setup for that. But "tx" on an ADC?

Rob
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Eugen Hristev Nov. 7, 2017, 8:49 a.m. | #4
On 20.10.2017 00:58, Rob Herring wrote:
> On Thu, Oct 19, 2017 at 6:14 AM, Alexandre Belloni
> <alexandre.belloni@free-electrons.com> wrote:
>> On 13/10/2017 at 16:51:42 -0500, Rob Herring wrote:
>>> On Wed, Oct 11, 2017 at 09:35:28AM +0300, Eugen Hristev wrote:
>>>> Added property for DMA configuration of the device.
>>>>
>>>> Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
>>>> ---
>>>>   Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt | 7 +++++++
>>>>   1 file changed, 7 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt b/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt
>>>> index 552e7a8..5f94d479 100644
>>>> --- a/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt
>>>> +++ b/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt
>>>> @@ -17,6 +17,11 @@ Required properties:
>>>>     This property uses the IRQ edge types values: IRQ_TYPE_EDGE_RISING ,
>>>>     IRQ_TYPE_EDGE_FALLING or IRQ_TYPE_EDGE_BOTH
>>>>
>>>> +Optional properties:
>>>> +  - dmas: Phandle to dma channel for the ADC.
>>>> +  See ../../dma/dma.txt for details.
>>>> +  - dma-names: Must be "rx" when dmas property is being used.
>>>
>>> -names is pointless when there is only one.
>>>
>>
>> You didn't reply to the question I had previously about that: What if at
>> some point, we have multiple dmas in the same binding?
> 
> Then add dma-names at that point and rx has to be first. If you know
> there's other channels, then add them now. Don't evolve the bindings
> needlessly based on what a driver supports.
> 
> Would another channel make sense here? Maybe multi-channel rx in which
> case your naming wouldn't be setup for that. But "tx" on an ADC?
> 
> Rob

Hello Rob,

I can keep only "dmas" and remove "dma-names", but then, the API used by
the drivers that request channels requires a name parameter
(dma_request_slave_channel), and it will look always inside the
"dma-names" property to match the name and find the proper channel, and
it will fail in this case.

Looking in the general dma binding (dma.txt) I can see that both
properties are marked as required for a client driver, so that's why
I added both.

I can either keep dma-names; or try to find the channel properties by
looking directly into the OF node and create the dma_chan struct inside
my driver (maybe call some xlate function for the DMA controller), but
still need to get the DT property. A complicated option would be to
actually create an API inside the dmaengine to find a channel without
name.

Which approach you think it's best to pursue ?

Thanks,
Eugen



> 
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Ludovic Desroches Nov. 7, 2017, 9:02 a.m. | #5
On Tue, Nov 07, 2017 at 10:49:41AM +0200, Eugen Hristev wrote:
> 
> 
> On 20.10.2017 00:58, Rob Herring wrote:
> > On Thu, Oct 19, 2017 at 6:14 AM, Alexandre Belloni
> > <alexandre.belloni@free-electrons.com> wrote:
> > > On 13/10/2017 at 16:51:42 -0500, Rob Herring wrote:
> > > > On Wed, Oct 11, 2017 at 09:35:28AM +0300, Eugen Hristev wrote:
> > > > > Added property for DMA configuration of the device.
> > > > > 
> > > > > Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
> > > > > ---
> > > > >   Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt | 7 +++++++
> > > > >   1 file changed, 7 insertions(+)
> > > > > 
> > > > > diff --git a/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt b/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt
> > > > > index 552e7a8..5f94d479 100644
> > > > > --- a/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt
> > > > > +++ b/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt
> > > > > @@ -17,6 +17,11 @@ Required properties:
> > > > >     This property uses the IRQ edge types values: IRQ_TYPE_EDGE_RISING ,
> > > > >     IRQ_TYPE_EDGE_FALLING or IRQ_TYPE_EDGE_BOTH
> > > > > 
> > > > > +Optional properties:
> > > > > +  - dmas: Phandle to dma channel for the ADC.
> > > > > +  See ../../dma/dma.txt for details.
> > > > > +  - dma-names: Must be "rx" when dmas property is being used.
> > > > 
> > > > -names is pointless when there is only one.
> > > > 
> > > 
> > > You didn't reply to the question I had previously about that: What if at
> > > some point, we have multiple dmas in the same binding?
> > 
> > Then add dma-names at that point and rx has to be first. If you know
> > there's other channels, then add them now. Don't evolve the bindings
> > needlessly based on what a driver supports.
> > 
> > Would another channel make sense here? Maybe multi-channel rx in which
> > case your naming wouldn't be setup for that. But "tx" on an ADC?
> > 
> > Rob
> 
> Hello Rob,
> 
> I can keep only "dmas" and remove "dma-names", but then, the API used by
> the drivers that request channels requires a name parameter
> (dma_request_slave_channel), and it will look always inside the
> "dma-names" property to match the name and find the proper channel, and
> it will fail in this case.
> 
> Looking in the general dma binding (dma.txt) I can see that both
> properties are marked as required for a client driver, so that's why
> I added both.
> 

I don't understand why dma-names should be removed. For sure, if we have
only one channel, it becomes useless but the helpers to get a dma channel
rely on dma-names property.

Ludovic

> I can either keep dma-names; or try to find the channel properties by
> looking directly into the OF node and create the dma_chan struct inside
> my driver (maybe call some xlate function for the DMA controller), but
> still need to get the DT property. A complicated option would be to
> actually create an API inside the dmaengine to find a channel without
> name.
> 
> Which approach you think it's best to pursue ?
> 
> Thanks,
> Eugen
> 
> 
> 
> > 
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Patch

diff --git a/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt b/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt
index 552e7a8..5f94d479 100644
--- a/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt
+++ b/Documentation/devicetree/bindings/iio/adc/at91-sama5d2_adc.txt
@@ -17,6 +17,11 @@  Required properties:
   This property uses the IRQ edge types values: IRQ_TYPE_EDGE_RISING ,
   IRQ_TYPE_EDGE_FALLING or IRQ_TYPE_EDGE_BOTH
 
+Optional properties:
+  - dmas: Phandle to dma channel for the ADC.
+  See ../../dma/dma.txt for details.
+  - dma-names: Must be "rx" when dmas property is being used.
+
 Example:
 
 adc: adc@fc030000 {
@@ -31,4 +36,6 @@  adc: adc@fc030000 {
 	vddana-supply = <&vdd_3v3_lp_reg>;
 	vref-supply = <&vdd_3v3_lp_reg>;
 	atmel,trigger-edge-type = <IRQ_TYPE_EDGE_BOTH>;
+	dmas = <&dma0 (AT91_XDMAC_DT_MEM_IF(0) | AT91_XDMAC_DT_PER_IF(1) | AT91_XDMAC_DT_PERID(25))>;
+	dma-names = "rx";
 }