[v1,2/2] dt-bindings: ASoC: simple-card: Add system-clock-id property

  This is a new per-DAI property used to specify the clock ID argument
to snd_soc_dai_set_sysclk().

Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@gmail.com>
---
 Documentation/devicetree/bindings/sound/simple-card.yaml | 8 ++++++++
 1 file changed, 8 insertions(+)
  

On 22/10/2022 12:27, Aidan MacDonald wrote:
> This is a new per-DAI property used to specify the clock ID argument
> to snd_soc_dai_set_sysclk().

You did no show the use of this property and here you refer to some
specific Linux driver implementation, so in total this does no look like
 a hardware property.

You also did not explain why do you need it (the most important piece of
commit msg).

> 
> Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@gmail.com>
> ---
>  Documentation/devicetree/bindings/sound/simple-card.yaml | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/sound/simple-card.yaml b/Documentation/devicetree/bindings/sound/simple-card.yaml
> index ed19899bc94b..cb7774e235d0 100644
> --- a/Documentation/devicetree/bindings/sound/simple-card.yaml
> +++ b/Documentation/devicetree/bindings/sound/simple-card.yaml
> @@ -57,6 +57,12 @@ definitions:
>        single fixed sampling rate.
>      $ref: /schemas/types.yaml#/definitions/flag
>  
> +  system-clock-id:
> +    description: |
> +      Specify the clock ID used for setting the DAI system clock.


With lack of explanation above, I would say - use common clock framework
to choose a clock...


Best regards,
Krzysztof
  

Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> writes:

> On 22/10/2022 12:27, Aidan MacDonald wrote:
>> This is a new per-DAI property used to specify the clock ID argument
>> to snd_soc_dai_set_sysclk().
>
> You did no show the use of this property and here you refer to some
> specific Linux driver implementation, so in total this does no look like
>  a hardware property.
>
> You also did not explain why do you need it (the most important piece of
> commit msg).
>
>>
>> Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@gmail.com>
>> ---
>>  Documentation/devicetree/bindings/sound/simple-card.yaml | 8 ++++++++
>>  1 file changed, 8 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/sound/simple-card.yaml b/Documentation/devicetree/bindings/sound/simple-card.yaml
>> index ed19899bc94b..cb7774e235d0 100644
>> --- a/Documentation/devicetree/bindings/sound/simple-card.yaml
>> +++ b/Documentation/devicetree/bindings/sound/simple-card.yaml
>> @@ -57,6 +57,12 @@ definitions:
>>        single fixed sampling rate.
>>      $ref: /schemas/types.yaml#/definitions/flag
>>
>> +  system-clock-id:
>> +    description: |
>> +      Specify the clock ID used for setting the DAI system clock.
>
>
> With lack of explanation above, I would say - use common clock framework
> to choose a clock...
>
>
> Best regards,
> Krzysztof

Sorry, I didn't explain things very well. The system clock ID is indeed
a property of the DAI hardware. The ID is not specific to Linux in any
way, and really it's an enumeration that requires a dt-binding.

A DAI may support multiple system clock inputs or outputs identified by
the clock ID. In the case of outputs, these could be distinct clocks
that have their own I/O pins, or the clock ID could select the internal
source clock used for a clock generator. For inputs, the system clock ID
may inform the DAI how or where the system clock is being provided so
hardware registers can be configured appropriately.

Really the details do not matter, except that in a particular DAI link
configuration a specific clock ID must be used. This is determined by
the actual hardware connection between the DAIs; if the wrong clock is
used, the DAI may not function correctly.

Currently the device tree is ambiguous as to which system clock should
be used when the DAI supports more than one, because there is no way to
specify which clock was intended. Linux just treats the ID as zero, but
that's currently a Linux-specific numbering so there's guarantee that
another OS would choose the same clock as Linux.

The system-clock-id property is therefore necessary to fully describe
the hardware connection between DAIs in a DAI link when a DAI offers
more than one choice of system clock.

I will resend the patch with the above in the commit message.

Regards,
Aidan
  

On 23/10/2022 09:47, Aidan MacDonald wrote:
> 
> Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> writes:
> 
>> On 22/10/2022 12:27, Aidan MacDonald wrote:
>>> This is a new per-DAI property used to specify the clock ID argument
>>> to snd_soc_dai_set_sysclk().
>>
>> You did no show the use of this property and here you refer to some
>> specific Linux driver implementation, so in total this does no look like
>>  a hardware property.
>>
>> You also did not explain why do you need it (the most important piece of
>> commit msg).
>>
>>>
>>> Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@gmail.com>
>>> ---
>>>  Documentation/devicetree/bindings/sound/simple-card.yaml | 8 ++++++++
>>>  1 file changed, 8 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/sound/simple-card.yaml b/Documentation/devicetree/bindings/sound/simple-card.yaml
>>> index ed19899bc94b..cb7774e235d0 100644
>>> --- a/Documentation/devicetree/bindings/sound/simple-card.yaml
>>> +++ b/Documentation/devicetree/bindings/sound/simple-card.yaml
>>> @@ -57,6 +57,12 @@ definitions:
>>>        single fixed sampling rate.
>>>      $ref: /schemas/types.yaml#/definitions/flag
>>>
>>> +  system-clock-id:
>>> +    description: |
>>> +      Specify the clock ID used for setting the DAI system clock.
>>
>>
>> With lack of explanation above, I would say - use common clock framework
>> to choose a clock...
>>
>>
>> Best regards,
>> Krzysztof
> 
> Sorry, I didn't explain things very well. The system clock ID is indeed
> a property of the DAI hardware. The ID is not specific to Linux in any
> way, and really it's an enumeration that requires a dt-binding.
> 
> A DAI may support multiple system clock inputs or outputs identified by
> the clock ID. In the case of outputs, these could be distinct clocks
> that have their own I/O pins, or the clock ID could select the internal
> source clock used for a clock generator. For inputs, the system clock ID
> may inform the DAI how or where the system clock is being provided so
> hardware registers can be configured appropriately.
> 
> Really the details do not matter, except that in a particular DAI link
> configuration a specific clock ID must be used. This is determined by
> the actual hardware connection between the DAIs; if the wrong clock is
> used, the DAI may not function correctly.
> 
> Currently the device tree is ambiguous as to which system clock should
> be used when the DAI supports more than one, because there is no way to
> specify which clock was intended. Linux just treats the ID as zero, but
> that's currently a Linux-specific numbering so there's guarantee that
> another OS would choose the same clock as Linux.
> 
> The system-clock-id property is therefore necessary to fully describe
> the hardware connection between DAIs in a DAI link when a DAI offers
> more than one choice of system clock.
> 
> I will resend the patch with the above in the commit message.

For example if you want to define which input pin to use (so you have
internal mux), it's quite unspecific to give them some indexes. What is
0? What is 1? Number of pin? Number of pin counting from where?

Since this is unanswered, the IDs are also driver and implementation
dependent, thus you still have the same problem - another OS can choose
different clock. That's not then a hardware description, but software
configuration.

Best regards,
Krzysztof
  

Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> writes:

> On 23/10/2022 09:47, Aidan MacDonald wrote:
>>
>> Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> writes:
>>
>>> On 22/10/2022 12:27, Aidan MacDonald wrote:
>>>> This is a new per-DAI property used to specify the clock ID argument
>>>> to snd_soc_dai_set_sysclk().
>>>
>>> You did no show the use of this property and here you refer to some
>>> specific Linux driver implementation, so in total this does no look like
>>>  a hardware property.
>>>
>>> You also did not explain why do you need it (the most important piece of
>>> commit msg).
>>>
>>>>
>>>> Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@gmail.com>
>>>> ---
>>>>  Documentation/devicetree/bindings/sound/simple-card.yaml | 8 ++++++++
>>>>  1 file changed, 8 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/sound/simple-card.yaml b/Documentation/devicetree/bindings/sound/simple-card.yaml
>>>> index ed19899bc94b..cb7774e235d0 100644
>>>> --- a/Documentation/devicetree/bindings/sound/simple-card.yaml
>>>> +++ b/Documentation/devicetree/bindings/sound/simple-card.yaml
>>>> @@ -57,6 +57,12 @@ definitions:
>>>>        single fixed sampling rate.
>>>>      $ref: /schemas/types.yaml#/definitions/flag
>>>>
>>>> +  system-clock-id:
>>>> +    description: |
>>>> +      Specify the clock ID used for setting the DAI system clock.
>>>
>>>
>>> With lack of explanation above, I would say - use common clock framework
>>> to choose a clock...
>>>
>>>
>>> Best regards,
>>> Krzysztof
>>
>> Sorry, I didn't explain things very well. The system clock ID is indeed
>> a property of the DAI hardware. The ID is not specific to Linux in any
>> way, and really it's an enumeration that requires a dt-binding.
>>
>> A DAI may support multiple system clock inputs or outputs identified by
>> the clock ID. In the case of outputs, these could be distinct clocks
>> that have their own I/O pins, or the clock ID could select the internal
>> source clock used for a clock generator. For inputs, the system clock ID
>> may inform the DAI how or where the system clock is being provided so
>> hardware registers can be configured appropriately.
>>
>> Really the details do not matter, except that in a particular DAI link
>> configuration a specific clock ID must be used. This is determined by
>> the actual hardware connection between the DAIs; if the wrong clock is
>> used, the DAI may not function correctly.
>>
>> Currently the device tree is ambiguous as to which system clock should
>> be used when the DAI supports more than one, because there is no way to
>> specify which clock was intended. Linux just treats the ID as zero, but
>> that's currently a Linux-specific numbering so there's guarantee that
>> another OS would choose the same clock as Linux.
>>
>> The system-clock-id property is therefore necessary to fully describe
>> the hardware connection between DAIs in a DAI link when a DAI offers
>> more than one choice of system clock.
>>
>> I will resend the patch with the above in the commit message.
>
> For example if you want to define which input pin to use (so you have
> internal mux), it's quite unspecific to give them some indexes. What is
> 0? What is 1? Number of pin? Number of pin counting from where?
>
> Since this is unanswered, the IDs are also driver and implementation
> dependent, thus you still have the same problem - another OS can choose
> different clock. That's not then a hardware description, but software
> configuration.
>
> Best regards,
> Krzysztof

I answered this already. The enumeration is arbitrary. Create some
dt-bindings and voila, it becomes standardized and OS-independent.

Regards,
Aidan
  

On 24/10/2022 19:38, Aidan MacDonald wrote:
> 
> Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> writes:
> 
>> On 23/10/2022 09:47, Aidan MacDonald wrote:
>>>
>>> Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> writes:
>>>
>>>> On 22/10/2022 12:27, Aidan MacDonald wrote:
>>>>> This is a new per-DAI property used to specify the clock ID argument
>>>>> to snd_soc_dai_set_sysclk().
>>>>
>>>> You did no show the use of this property and here you refer to some
>>>> specific Linux driver implementation, so in total this does no look like
>>>>  a hardware property.
>>>>
>>>> You also did not explain why do you need it (the most important piece of
>>>> commit msg).
>>>>
>>>>>
>>>>> Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@gmail.com>
>>>>> ---
>>>>>  Documentation/devicetree/bindings/sound/simple-card.yaml | 8 ++++++++
>>>>>  1 file changed, 8 insertions(+)
>>>>>
>>>>> diff --git a/Documentation/devicetree/bindings/sound/simple-card.yaml b/Documentation/devicetree/bindings/sound/simple-card.yaml
>>>>> index ed19899bc94b..cb7774e235d0 100644
>>>>> --- a/Documentation/devicetree/bindings/sound/simple-card.yaml
>>>>> +++ b/Documentation/devicetree/bindings/sound/simple-card.yaml
>>>>> @@ -57,6 +57,12 @@ definitions:
>>>>>        single fixed sampling rate.
>>>>>      $ref: /schemas/types.yaml#/definitions/flag
>>>>>
>>>>> +  system-clock-id:
>>>>> +    description: |
>>>>> +      Specify the clock ID used for setting the DAI system clock.
>>>>
>>>>
>>>> With lack of explanation above, I would say - use common clock framework
>>>> to choose a clock...
>>>>
>>>>
>>>> Best regards,
>>>> Krzysztof
>>>
>>> Sorry, I didn't explain things very well. The system clock ID is indeed
>>> a property of the DAI hardware. The ID is not specific to Linux in any
>>> way, and really it's an enumeration that requires a dt-binding.
>>>
>>> A DAI may support multiple system clock inputs or outputs identified by
>>> the clock ID. In the case of outputs, these could be distinct clocks
>>> that have their own I/O pins, or the clock ID could select the internal
>>> source clock used for a clock generator. For inputs, the system clock ID
>>> may inform the DAI how or where the system clock is being provided so
>>> hardware registers can be configured appropriately.
>>>
>>> Really the details do not matter, except that in a particular DAI link
>>> configuration a specific clock ID must be used. This is determined by
>>> the actual hardware connection between the DAIs; if the wrong clock is
>>> used, the DAI may not function correctly.
>>>
>>> Currently the device tree is ambiguous as to which system clock should
>>> be used when the DAI supports more than one, because there is no way to
>>> specify which clock was intended. Linux just treats the ID as zero, but
>>> that's currently a Linux-specific numbering so there's guarantee that
>>> another OS would choose the same clock as Linux.
>>>
>>> The system-clock-id property is therefore necessary to fully describe
>>> the hardware connection between DAIs in a DAI link when a DAI offers
>>> more than one choice of system clock.
>>>
>>> I will resend the patch with the above in the commit message.
>>
>> For example if you want to define which input pin to use (so you have
>> internal mux), it's quite unspecific to give them some indexes. What is
>> 0? What is 1? Number of pin? Number of pin counting from where?
>>
>> Since this is unanswered, the IDs are also driver and implementation
>> dependent, thus you still have the same problem - another OS can choose
>> different clock. That's not then a hardware description, but software
>> configuration.
>>
>> Best regards,
>> Krzysztof
> 
> I answered this already. The enumeration is arbitrary. Create some
> dt-bindings and voila, it becomes standardized and OS-independent.

Hm, then I missed something. Can you point me to DTS and bindings
(patches or in-tree) which show this standardized indices of clock inputs?

Best regards,
Krzysztof
  

Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> writes:

> On 24/10/2022 19:38, Aidan MacDonald wrote:
>>
>> Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> writes:
>>
>>> On 23/10/2022 09:47, Aidan MacDonald wrote:
>>>>
>>>> Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> writes:
>>>>
>>>>> On 22/10/2022 12:27, Aidan MacDonald wrote:
>>>>>> This is a new per-DAI property used to specify the clock ID argument
>>>>>> to snd_soc_dai_set_sysclk().
>>>>>
>>>>> You did no show the use of this property and here you refer to some
>>>>> specific Linux driver implementation, so in total this does no look like
>>>>>  a hardware property.
>>>>>
>>>>> You also did not explain why do you need it (the most important piece of
>>>>> commit msg).
>>>>>
>>>>>>
>>>>>> Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@gmail.com>
>>>>>> ---
>>>>>>  Documentation/devicetree/bindings/sound/simple-card.yaml | 8 ++++++++
>>>>>>  1 file changed, 8 insertions(+)
>>>>>>
>>>>>> diff --git a/Documentation/devicetree/bindings/sound/simple-card.yaml b/Documentation/devicetree/bindings/sound/simple-card.yaml
>>>>>> index ed19899bc94b..cb7774e235d0 100644
>>>>>> --- a/Documentation/devicetree/bindings/sound/simple-card.yaml
>>>>>> +++ b/Documentation/devicetree/bindings/sound/simple-card.yaml
>>>>>> @@ -57,6 +57,12 @@ definitions:
>>>>>>        single fixed sampling rate.
>>>>>>      $ref: /schemas/types.yaml#/definitions/flag
>>>>>>
>>>>>> +  system-clock-id:
>>>>>> +    description: |
>>>>>> +      Specify the clock ID used for setting the DAI system clock.
>>>>>
>>>>>
>>>>> With lack of explanation above, I would say - use common clock framework
>>>>> to choose a clock...
>>>>>
>>>>>
>>>>> Best regards,
>>>>> Krzysztof
>>>>
>>>> Sorry, I didn't explain things very well. The system clock ID is indeed
>>>> a property of the DAI hardware. The ID is not specific to Linux in any
>>>> way, and really it's an enumeration that requires a dt-binding.
>>>>
>>>> A DAI may support multiple system clock inputs or outputs identified by
>>>> the clock ID. In the case of outputs, these could be distinct clocks
>>>> that have their own I/O pins, or the clock ID could select the internal
>>>> source clock used for a clock generator. For inputs, the system clock ID
>>>> may inform the DAI how or where the system clock is being provided so
>>>> hardware registers can be configured appropriately.
>>>>
>>>> Really the details do not matter, except that in a particular DAI link
>>>> configuration a specific clock ID must be used. This is determined by
>>>> the actual hardware connection between the DAIs; if the wrong clock is
>>>> used, the DAI may not function correctly.
>>>>
>>>> Currently the device tree is ambiguous as to which system clock should
>>>> be used when the DAI supports more than one, because there is no way to
>>>> specify which clock was intended. Linux just treats the ID as zero, but
>>>> that's currently a Linux-specific numbering so there's guarantee that
>>>> another OS would choose the same clock as Linux.
>>>>
>>>> The system-clock-id property is therefore necessary to fully describe
>>>> the hardware connection between DAIs in a DAI link when a DAI offers
>>>> more than one choice of system clock.
>>>>
>>>> I will resend the patch with the above in the commit message.
>>>
>>> For example if you want to define which input pin to use (so you have
>>> internal mux), it's quite unspecific to give them some indexes. What is
>>> 0? What is 1? Number of pin? Number of pin counting from where?
>>>
>>> Since this is unanswered, the IDs are also driver and implementation
>>> dependent, thus you still have the same problem - another OS can choose
>>> different clock. That's not then a hardware description, but software
>>> configuration.
>>>
>>> Best regards,
>>> Krzysztof
>>
>> I answered this already. The enumeration is arbitrary. Create some
>> dt-bindings and voila, it becomes standardized and OS-independent.
>
> Hm, then I missed something. Can you point me to DTS and bindings
> (patches or in-tree) which show this standardized indices of clock inputs?
>
> Best regards,
> Krzysztof

Device trees already use standardized enumerations in other areas so it
isn't a new idea. Look under include/dt-bindings/clock. Every header
there contains an arbitrary enumeration of a device's clocks. In fact
most of include/dt-bindings is exactly for this purpose, to define
standard values that are not "just numbers" but an enum, a flag, etc,
with a special meaning. It is not specific to clocks.

There is no dt-binding for system clock ID, because prior to this patch
they were not exposed to DT in any way. But the enumerations themselves
already exist, eg. the IDs for nau8821 codec:

    /* System Clock Source */
    enum {
        NAU8821_CLK_DIS,
        NAU8821_CLK_MCLK,
        NAU8821_CLK_INTERNAL,
        NAU8821_CLK_FLL_MCLK,
        NAU8821_CLK_FLL_BLK,
        NAU8821_CLK_FLL_FS,
    };

We would just be moving these into dt-bindings if somebody wants to
use a codec with simple-card. Future drivers would add the enum into
dt-bindings from the start because that's where it belongs.

Regards,
Aidan
  

On 25/10/2022 05:14, Aidan MacDonald wrote:
>> Krzysztof
> 
> Device trees already use standardized enumerations in other areas so it
> isn't a new idea. Look under include/dt-bindings/clock. Every header
> there contains an arbitrary enumeration of a device's clocks. In fact
> most of include/dt-bindings is exactly for this purpose, to define
> standard values that are not "just numbers" but an enum, a flag, etc,
> with a special meaning. It is not specific to clocks.
> 
> There is no dt-binding for system clock ID, because prior to this patch
> they were not exposed to DT in any way. But the enumerations themselves
> already exist, eg. the IDs for nau8821 codec:
> 
>     /* System Clock Source */
>     enum {
>         NAU8821_CLK_DIS,
>         NAU8821_CLK_MCLK,
>         NAU8821_CLK_INTERNAL,
>         NAU8821_CLK_FLL_MCLK,
>         NAU8821_CLK_FLL_BLK,
>         NAU8821_CLK_FLL_FS,
>     };

OK, this looks good.

> 
> We would just be moving these into dt-bindings if somebody wants to
> use a codec with simple-card. Future drivers would add the enum into
> dt-bindings from the start because that's where it belongs.

And the remaining piece I don't get is that these are not bindings for
codec, but for sound audio card. You want to set "system-clock-id"
property for audio card, while putting clock from codec, which will be
used to pass back to the codec... so it is a property of the codec, not
of the audio card. IOW, NAU8821_CLK_* does not configure here the clock
of the system, but only, only clock of the codec.



Best regards,
Krzysztof
  

Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> writes:

> And the remaining piece I don't get is that these are not bindings for
> codec, but for sound audio card. You want to set "system-clock-id"
> property for audio card, while putting clock from codec, which will be
> used to pass back to the codec... so it is a property of the codec, not
> of the audio card. IOW, NAU8821_CLK_* does not configure here the clock
> of the system, but only, only clock of the codec.

The system clock is controlled at the DAI level, it's specific to one
DAI on one component. The simple-card device node has sub-nodes for the
DAI links, and each DAI link node has sub-nodes for the DAIs within the
link. "system-clock-id" is a property on the DAI nodes, so it's not a
card-level property, just one part of the overall card definition.

Since the clock ID is something defined by the codec it would naturally
be a value defined by the codec, but the *configuration* of the codec is
part of the sound card because it depends on how everything is connected
together. If you used the same codec in a different machine it would
have a different configuration.

Regards,
Aidan
  

On 26/10/2022 10:48, Aidan MacDonald wrote:
> 
> Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> writes:
> 
>> And the remaining piece I don't get is that these are not bindings for
>> codec, but for sound audio card. You want to set "system-clock-id"
>> property for audio card, while putting clock from codec, which will be
>> used to pass back to the codec... so it is a property of the codec, not
>> of the audio card. IOW, NAU8821_CLK_* does not configure here the clock
>> of the system, but only, only clock of the codec.
> 
> The system clock is controlled at the DAI level, it's specific to one
> DAI on one component. The simple-card device node has sub-nodes for the
> DAI links, and each DAI link node has sub-nodes for the DAIs within the
> link. "system-clock-id" is a property on the DAI nodes, so it's not a
> card-level property, just one part of the overall card definition.
> 
> Since the clock ID is something defined by the codec it would naturally
> be a value defined by the codec, but the *configuration* of the codec is
> part of the sound card because it depends on how everything is connected
> together. If you used the same codec in a different machine it would
> have a different configuration.


OK, that sounds reasonable. Thank you for explaining this. You still
need to convince Mark :)

Best regards,
Krzysztof
  

On 22/10/2022 12:27, Aidan MacDonald wrote:
> This is a new per-DAI property used to specify the clock ID argument
> to snd_soc_dai_set_sysclk().
> 
> Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@gmail.com>
> ---
>  Documentation/devicetree/bindings/sound/simple-card.yaml | 8 ++++++++
>  1 file changed, 8 insertions(+)

My concerns were addressed, so:

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Best regards,
Krzysztof
  

Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> writes:

> On 26/10/2022 10:48, Aidan MacDonald wrote:
>>
>> Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> writes:
>>
>>> And the remaining piece I don't get is that these are not bindings for
>>> codec, but for sound audio card. You want to set "system-clock-id"
>>> property for audio card, while putting clock from codec, which will be
>>> used to pass back to the codec... so it is a property of the codec, not
>>> of the audio card. IOW, NAU8821_CLK_* does not configure here the clock
>>> of the system, but only, only clock of the codec.
>>
>> The system clock is controlled at the DAI level, it's specific to one
>> DAI on one component. The simple-card device node has sub-nodes for the
>> DAI links, and each DAI link node has sub-nodes for the DAIs within the
>> link. "system-clock-id" is a property on the DAI nodes, so it's not a
>> card-level property, just one part of the overall card definition.
>>
>> Since the clock ID is something defined by the codec it would naturally
>> be a value defined by the codec, but the *configuration* of the codec is
>> part of the sound card because it depends on how everything is connected
>> together. If you used the same codec in a different machine it would
>> have a different configuration.
>
> OK, that sounds reasonable. Thank you for explaining this. You still
> need to convince Mark :)

No problem, thanks for bearing with all my explanations! Mark raised
some good points, and I have to agree with him. This could create too
many future issues, and the problem might be better solved with the
clock API -- but unfortunately that's not yet feasible.

Regards,
Aidan