[PATCH 2/4] dt-bindings: arm: mediatek: Add new bindings of MediaTek frequency hopping

Johnson Wang posted 4 patches 2 years ago
There is a newer version of this series
[PATCH 2/4] dt-bindings: arm: mediatek: Add new bindings of MediaTek frequency hopping
Posted by Johnson Wang 2 years ago
Add the new binding documentation for MediaTek frequency hopping
and spread spectrum clocking control.

Co-developed-by: Edward-JW Yang <edward-jw.yang@mediatek.com>
Signed-off-by: Edward-JW Yang <edward-jw.yang@mediatek.com>
Signed-off-by: Johnson Wang <johnson.wang@mediatek.com>
---
 .../bindings/arm/mediatek/mediatek,fhctl.yaml | 49 +++++++++++++++++++
 1 file changed, 49 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yaml

diff --git a/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yaml b/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yaml
new file mode 100644
index 000000000000..c5d76410538b
--- /dev/null
+++ b/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yaml
@@ -0,0 +1,49 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/arm/mediatek/mediatek,fhctl.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: MediaTek frequency hopping and spread spectrum clocking control
+
+maintainers:
+  - Edward-JW Yang <edward-jw.yang@mediatek.com>
+
+description: |
+  Frequency hopping control (FHCTL) is a piece of hardware that control
+  some PLLs to adopt "hopping" mechanism to adjust their frequency.
+  Spread spectrum clocking (SSC) is another function provided by this hardware.
+
+properties:
+  compatible:
+    const: mediatek,fhctl
+
+  reg:
+    maxItems: 1
+
+  mediatek,hopping-ssc-percents:
+    description: |
+      Determine the enablement of frequency hopping feature and the percentage
+      of spread spectrum clocking for PLLs.
+    $ref: /schemas/types.yaml#/definitions/uint32-matrix
+    items:
+      items:
+        - description: PLL id that is expected to enable frequency hopping.
+        - description: The percentage of spread spectrum clocking for one PLL.
+          minimum: 0
+          maximum: 8
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/clock/mt8186-clk.h>
+    fhctl: fhctl@1000ce00 {
+        compatible = "mediatek,fhctl";
+        reg = <0x1000c000 0xe00>;
+        mediatek,hopping-ssc-percents = <CLK_APMIXED_MSDCPLL 3>;
+    };
-- 
2.18.0
Re: [PATCH 2/4] dt-bindings: arm: mediatek: Add new bindings of MediaTek frequency hopping
Posted by Krzysztof Kozlowski 2 years ago
On 31/08/2022 15:48, Johnson Wang wrote:
> Add the new binding documentation for MediaTek frequency hopping
> and spread spectrum clocking control.
> 
> Co-developed-by: Edward-JW Yang <edward-jw.yang@mediatek.com>
> Signed-off-by: Edward-JW Yang <edward-jw.yang@mediatek.com>
> Signed-off-by: Johnson Wang <johnson.wang@mediatek.com>
> ---
>  .../bindings/arm/mediatek/mediatek,fhctl.yaml | 49 +++++++++++++++++++
>  1 file changed, 49 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yaml
> 
> diff --git a/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yaml b/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yaml
> new file mode 100644
> index 000000000000..c5d76410538b
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yaml
> @@ -0,0 +1,49 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/arm/mediatek/mediatek,fhctl.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: MediaTek frequency hopping and spread spectrum clocking control
> +
> +maintainers:
> +  - Edward-JW Yang <edward-jw.yang@mediatek.com>
> +
> +description: |
> +  Frequency hopping control (FHCTL) is a piece of hardware that control
> +  some PLLs to adopt "hopping" mechanism to adjust their frequency.
> +  Spread spectrum clocking (SSC) is another function provided by this hardware.
> +
> +properties:
> +  compatible:
> +    const: mediatek,fhctl

You need SoC/device specific compatibles. Preferably only SoC specific,
without generic fallback, unless you can guarantee (while representing
MediaTek), that generic fallback will cover all of their SoCs?

> +
> +  reg:
> +    maxItems: 1
> +
> +  mediatek,hopping-ssc-percents:
> +    description: |
> +      Determine the enablement of frequency hopping feature and the percentage
> +      of spread spectrum clocking for PLLs.
> +    $ref: /schemas/types.yaml#/definitions/uint32-matrix
> +    items:
> +      items:
> +        - description: PLL id that is expected to enable frequency hopping.

So the clocks are indices from some specific, yet unnamed
clock-controller? This feels hacky. You should rather take here clock
phandles (1) or integrate it into specific clock controller (2). The
reason is that either your device does something on top of existing
clocks (option 1, thus it takes clock as inputs) or it modifies existing
clocks (option 2, thus it is integral part of clock-controller).


Best regards,
Krzysztof
Re: [PATCH 2/4] dt-bindings: arm: mediatek: Add new bindings of MediaTek frequency hopping
Posted by Johnson Wang 2 years ago
On Wed, 2022-08-31 at 16:19 +0300, Krzysztof Kozlowski wrote:
> On 31/08/2022 15:48, Johnson Wang wrote:
> > Add the new binding documentation for MediaTek frequency hopping
> > and spread spectrum clocking control.
> > 
> > Co-developed-by: Edward-JW Yang <edward-jw.yang@mediatek.com>
> > Signed-off-by: Edward-JW Yang <edward-jw.yang@mediatek.com>
> > Signed-off-by: Johnson Wang <johnson.wang@mediatek.com>
> > ---
> >  .../bindings/arm/mediatek/mediatek,fhctl.yaml | 49
> > +++++++++++++++++++
> >  1 file changed, 49 insertions(+)
> >  create mode 100644
> > Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yaml
> > 
> > diff --git
> > a/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yam
> > l
> > b/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yam
> > l
> > new file mode 100644
> > index 000000000000..c5d76410538b
> > --- /dev/null
> > +++
> > b/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yam
> > l
> > @@ -0,0 +1,49 @@
> > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: 
> > https://urldefense.com/v3/__http://devicetree.org/schemas/arm/mediatek/mediatek,fhctl.yaml*__;Iw!!CTRNKA9wMg0ARbw!ysl-bMp7yP9Ym70o6EVB8A36MBxcXGap8doEKR_SbaAQSy8-_RU5jvrWTjzETut_6eXNGut4j-3dY0q7xJdpQbmaOw$
> >  
> > +$schema: 
> > https://urldefense.com/v3/__http://devicetree.org/meta-schemas/core.yaml*__;Iw!!CTRNKA9wMg0ARbw!ysl-bMp7yP9Ym70o6EVB8A36MBxcXGap8doEKR_SbaAQSy8-_RU5jvrWTjzETut_6eXNGut4j-3dY0q7xJezt7_RBw$
> >  
> > +
> > +title: MediaTek frequency hopping and spread spectrum clocking
> > control
> > +
> > +maintainers:
> > +  - Edward-JW Yang <edward-jw.yang@mediatek.com>
> > +
> > +description: |
> > +  Frequency hopping control (FHCTL) is a piece of hardware that
> > control
> > +  some PLLs to adopt "hopping" mechanism to adjust their
> > frequency.
> > +  Spread spectrum clocking (SSC) is another function provided by
> > this hardware.
> > +
> > +properties:
> > +  compatible:
> > +    const: mediatek,fhctl
> 
> You need SoC/device specific compatibles. Preferably only SoC
> specific,
> without generic fallback, unless you can guarantee (while
> representing
> MediaTek), that generic fallback will cover all of their SoCs?
> 

Hi Krzysztof,

At this moment, we plan to support FHCTL feature for MT8186 only.

If you prefer SoC-specific compatble, we will improve that in the next
version.

Thanks for your suggestion.

BRs,
Johnson Wang
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  mediatek,hopping-ssc-percents:
> > +    description: |
> > +      Determine the enablement of frequency hopping feature and
> > the percentage
> > +      of spread spectrum clocking for PLLs.
> > +    $ref: /schemas/types.yaml#/definitions/uint32-matrix
> > +    items:
> > +      items:
> > +        - description: PLL id that is expected to enable frequency
> > hopping.
> 
> So the clocks are indices from some specific, yet unnamed
> clock-controller? This feels hacky. You should rather take here clock
> phandles (1) or integrate it into specific clock controller (2). The
> reason is that either your device does something on top of existing
> clocks (option 1, thus it takes clock as inputs) or it modifies
> existing
> clocks (option 2, thus it is integral part of clock-controller).
> 
> 
> Best regards,
> Krzysztof
Re: [PATCH 2/4] dt-bindings: arm: mediatek: Add new bindings of MediaTek frequency hopping
Posted by Krzysztof Kozlowski 2 years ago
On 02/09/2022 08:39, Johnson Wang wrote:
> On Wed, 2022-08-31 at 16:19 +0300, Krzysztof Kozlowski wrote:
>> On 31/08/2022 15:48, Johnson Wang wrote:
>>> Add the new binding documentation for MediaTek frequency hopping
>>> and spread spectrum clocking control.
>>>
>>> Co-developed-by: Edward-JW Yang <edward-jw.yang@mediatek.com>
>>> Signed-off-by: Edward-JW Yang <edward-jw.yang@mediatek.com>
>>> Signed-off-by: Johnson Wang <johnson.wang@mediatek.com>
>>> ---
>>>  .../bindings/arm/mediatek/mediatek,fhctl.yaml | 49
>>> +++++++++++++++++++
>>>  1 file changed, 49 insertions(+)
>>>  create mode 100644
>>> Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yaml
>>>
>>> diff --git
>>> a/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yam
>>> l
>>> b/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yam
>>> l
>>> new file mode 100644
>>> index 000000000000..c5d76410538b
>>> --- /dev/null
>>> +++
>>> b/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yam
>>> l
>>> @@ -0,0 +1,49 @@
>>> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
>>> +%YAML 1.2
>>> +---
>>> +$id: 
>>> https://urldefense.com/v3/__http://devicetree.org/schemas/arm/mediatek/mediatek,fhctl.yaml*__;Iw!!CTRNKA9wMg0ARbw!ysl-bMp7yP9Ym70o6EVB8A36MBxcXGap8doEKR_SbaAQSy8-_RU5jvrWTjzETut_6eXNGut4j-3dY0q7xJdpQbmaOw$
>>>  
>>> +$schema: 
>>> https://urldefense.com/v3/__http://devicetree.org/meta-schemas/core.yaml*__;Iw!!CTRNKA9wMg0ARbw!ysl-bMp7yP9Ym70o6EVB8A36MBxcXGap8doEKR_SbaAQSy8-_RU5jvrWTjzETut_6eXNGut4j-3dY0q7xJezt7_RBw$
>>>  
>>> +
>>> +title: MediaTek frequency hopping and spread spectrum clocking
>>> control
>>> +
>>> +maintainers:
>>> +  - Edward-JW Yang <edward-jw.yang@mediatek.com>
>>> +
>>> +description: |
>>> +  Frequency hopping control (FHCTL) is a piece of hardware that
>>> control
>>> +  some PLLs to adopt "hopping" mechanism to adjust their
>>> frequency.
>>> +  Spread spectrum clocking (SSC) is another function provided by
>>> this hardware.
>>> +
>>> +properties:
>>> +  compatible:
>>> +    const: mediatek,fhctl
>>
>> You need SoC/device specific compatibles. Preferably only SoC
>> specific,
>> without generic fallback, unless you can guarantee (while
>> representing
>> MediaTek), that generic fallback will cover all of their SoCs?
>>
> 
> Hi Krzysztof,
> 
> At this moment, we plan to support FHCTL feature for MT8186 only.
> 
> If you prefer SoC-specific compatble, we will improve that in the next
> version.

Then make it only for mt8186.

Best regards,
Krzysztof
Re: [PATCH 2/4] dt-bindings: arm: mediatek: Add new bindings of MediaTek frequency hopping
Posted by AngeloGioacchino Del Regno 2 years ago
Il 31/08/22 15:19, Krzysztof Kozlowski ha scritto:
> On 31/08/2022 15:48, Johnson Wang wrote:
>> Add the new binding documentation for MediaTek frequency hopping
>> and spread spectrum clocking control.
>>
>> Co-developed-by: Edward-JW Yang <edward-jw.yang@mediatek.com>
>> Signed-off-by: Edward-JW Yang <edward-jw.yang@mediatek.com>
>> Signed-off-by: Johnson Wang <johnson.wang@mediatek.com>
>> ---
>>   .../bindings/arm/mediatek/mediatek,fhctl.yaml | 49 +++++++++++++++++++
>>   1 file changed, 49 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yaml b/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yaml
>> new file mode 100644
>> index 000000000000..c5d76410538b
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yaml
>> @@ -0,0 +1,49 @@
>> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/arm/mediatek/mediatek,fhctl.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: MediaTek frequency hopping and spread spectrum clocking control
>> +
>> +maintainers:
>> +  - Edward-JW Yang <edward-jw.yang@mediatek.com>
>> +
>> +description: |
>> +  Frequency hopping control (FHCTL) is a piece of hardware that control
>> +  some PLLs to adopt "hopping" mechanism to adjust their frequency.
>> +  Spread spectrum clocking (SSC) is another function provided by this hardware.
>> +
>> +properties:
>> +  compatible:
>> +    const: mediatek,fhctl
> 
> You need SoC/device specific compatibles. Preferably only SoC specific,
> without generic fallback, unless you can guarantee (while representing
> MediaTek), that generic fallback will cover all of their SoCs?
> 
>> +
>> +  reg:
>> +    maxItems: 1
>> +
>> +  mediatek,hopping-ssc-percents:
>> +    description: |
>> +      Determine the enablement of frequency hopping feature and the percentage
>> +      of spread spectrum clocking for PLLs.
>> +    $ref: /schemas/types.yaml#/definitions/uint32-matrix
>> +    items:
>> +      items:
>> +        - description: PLL id that is expected to enable frequency hopping.
> 
> So the clocks are indices from some specific, yet unnamed
> clock-controller? This feels hacky. You should rather take here clock
> phandles (1) or integrate it into specific clock controller (2). The
> reason is that either your device does something on top of existing
> clocks (option 1, thus it takes clock as inputs) or it modifies existing
> clocks (option 2, thus it is integral part of clock-controller).
> 

FHCTL is a MCU that handles (some, or all, depending on what's supported on the
SoC and what's needed by the board) PLL frequency setting, doing it in steps and
avoiding overshooting and other issues.

We had a pretty big conversation about this a while ago and the indices instead
of phandles is actually my fault, that happened because I initially proposed your
option 2 but then for a number of reasons we went with this kind of solution.

I know it's going to be a long read, but the entire conversation is on the list [1]

Cheers,
Angelo

[1]: 
https://patchwork.kernel.org/project/linux-mediatek/patch/20220612135414.3003-3-johnson.wang@mediatek.com/

> 
> Best regards,
> Krzysztof
Re: [PATCH 2/4] dt-bindings: arm: mediatek: Add new bindings of MediaTek frequency hopping
Posted by Krzysztof Kozlowski 2 years ago
On 01/09/2022 11:04, AngeloGioacchino Del Regno wrote:
> I know it's going to be a long read, but the entire conversation is on the list [1]
> 
> Cheers,
> Angelo
> 
> [1]: 
> https://patchwork.kernel.org/project/linux-mediatek/patch/20220612135414.3003-3-johnson.wang@mediatek.com/

I see there hundreds of lines of quoted text without trimming to actual
parts, so no, no one is going to read it.

Best regards,
Krzysztof
Re: [PATCH 2/4] dt-bindings: arm: mediatek: Add new bindings of MediaTek frequency hopping
Posted by Krzysztof Kozlowski 2 years ago
On 01/09/2022 11:04, AngeloGioacchino Del Regno wrote:
> Il 31/08/22 15:19, Krzysztof Kozlowski ha scritto:
>> On 31/08/2022 15:48, Johnson Wang wrote:
>>> Add the new binding documentation for MediaTek frequency hopping
>>> and spread spectrum clocking control.
>>>
>>> Co-developed-by: Edward-JW Yang <edward-jw.yang@mediatek.com>
>>> Signed-off-by: Edward-JW Yang <edward-jw.yang@mediatek.com>
>>> Signed-off-by: Johnson Wang <johnson.wang@mediatek.com>
>>> ---
>>>   .../bindings/arm/mediatek/mediatek,fhctl.yaml | 49 +++++++++++++++++++
>>>   1 file changed, 49 insertions(+)
>>>   create mode 100644 Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yaml
>>>
>>> diff --git a/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yaml b/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yaml
>>> new file mode 100644
>>> index 000000000000..c5d76410538b
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yaml
>>> @@ -0,0 +1,49 @@
>>> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
>>> +%YAML 1.2
>>> +---
>>> +$id: http://devicetree.org/schemas/arm/mediatek/mediatek,fhctl.yaml#
>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>> +
>>> +title: MediaTek frequency hopping and spread spectrum clocking control
>>> +
>>> +maintainers:
>>> +  - Edward-JW Yang <edward-jw.yang@mediatek.com>
>>> +
>>> +description: |
>>> +  Frequency hopping control (FHCTL) is a piece of hardware that control
>>> +  some PLLs to adopt "hopping" mechanism to adjust their frequency.
>>> +  Spread spectrum clocking (SSC) is another function provided by this hardware.
>>> +
>>> +properties:
>>> +  compatible:
>>> +    const: mediatek,fhctl
>>
>> You need SoC/device specific compatibles. Preferably only SoC specific,
>> without generic fallback, unless you can guarantee (while representing
>> MediaTek), that generic fallback will cover all of their SoCs?
>>
>>> +
>>> +  reg:
>>> +    maxItems: 1
>>> +
>>> +  mediatek,hopping-ssc-percents:
>>> +    description: |
>>> +      Determine the enablement of frequency hopping feature and the percentage
>>> +      of spread spectrum clocking for PLLs.
>>> +    $ref: /schemas/types.yaml#/definitions/uint32-matrix
>>> +    items:
>>> +      items:
>>> +        - description: PLL id that is expected to enable frequency hopping.
>>
>> So the clocks are indices from some specific, yet unnamed
>> clock-controller? This feels hacky. You should rather take here clock
>> phandles (1) or integrate it into specific clock controller (2). The
>> reason is that either your device does something on top of existing
>> clocks (option 1, thus it takes clock as inputs) or it modifies existing
>> clocks (option 2, thus it is integral part of clock-controller).
>>
> 
> FHCTL is a MCU that handles (some, or all, depending on what's supported on the
> SoC and what's needed by the board) PLL frequency setting, doing it in steps and
> avoiding overshooting and other issues.
> 
> We had a pretty big conversation about this a while ago and the indices instead
> of phandles is actually my fault, that happened because I initially proposed your
> option 2 but then for a number of reasons we went with this kind of solution.
> 
> I know it's going to be a long read, but the entire conversation is on the list [1]
> 

Sorry, but it's a hacky architecture where one device (which is a clock
provider) and second device have no relationship in hardware description
but both play with each other resources. That's simply not a proper
hardware description, so again:

1. If this is separate device (as you indicated), then it needs
expressing the dependencies and uses of other device resources.

2. If this is not a separate device, but integral part of clock
controller, then it would be fine but then probably should be child of
that device.

Best regards,
Krzysztof
Re: [PATCH 2/4] dt-bindings: arm: mediatek: Add new bindings of MediaTek frequency hopping
Posted by AngeloGioacchino Del Regno 2 years ago
Il 01/09/22 11:42, Krzysztof Kozlowski ha scritto:
> On 01/09/2022 11:04, AngeloGioacchino Del Regno wrote:
>> Il 31/08/22 15:19, Krzysztof Kozlowski ha scritto:
>>> On 31/08/2022 15:48, Johnson Wang wrote:
>>>> Add the new binding documentation for MediaTek frequency hopping
>>>> and spread spectrum clocking control.
>>>>
>>>> Co-developed-by: Edward-JW Yang <edward-jw.yang@mediatek.com>
>>>> Signed-off-by: Edward-JW Yang <edward-jw.yang@mediatek.com>
>>>> Signed-off-by: Johnson Wang <johnson.wang@mediatek.com>
>>>> ---
>>>>    .../bindings/arm/mediatek/mediatek,fhctl.yaml | 49 +++++++++++++++++++
>>>>    1 file changed, 49 insertions(+)
>>>>    create mode 100644 Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yaml
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yaml b/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yaml
>>>> new file mode 100644
>>>> index 000000000000..c5d76410538b
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/arm/mediatek/mediatek,fhctl.yaml
>>>> @@ -0,0 +1,49 @@
>>>> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
>>>> +%YAML 1.2
>>>> +---
>>>> +$id: http://devicetree.org/schemas/arm/mediatek/mediatek,fhctl.yaml#
>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>>> +
>>>> +title: MediaTek frequency hopping and spread spectrum clocking control
>>>> +
>>>> +maintainers:
>>>> +  - Edward-JW Yang <edward-jw.yang@mediatek.com>
>>>> +
>>>> +description: |
>>>> +  Frequency hopping control (FHCTL) is a piece of hardware that control
>>>> +  some PLLs to adopt "hopping" mechanism to adjust their frequency.
>>>> +  Spread spectrum clocking (SSC) is another function provided by this hardware.
>>>> +
>>>> +properties:
>>>> +  compatible:
>>>> +    const: mediatek,fhctl
>>>
>>> You need SoC/device specific compatibles. Preferably only SoC specific,
>>> without generic fallback, unless you can guarantee (while representing
>>> MediaTek), that generic fallback will cover all of their SoCs?
>>>
>>>> +
>>>> +  reg:
>>>> +    maxItems: 1
>>>> +
>>>> +  mediatek,hopping-ssc-percents:
>>>> +    description: |
>>>> +      Determine the enablement of frequency hopping feature and the percentage
>>>> +      of spread spectrum clocking for PLLs.
>>>> +    $ref: /schemas/types.yaml#/definitions/uint32-matrix
>>>> +    items:
>>>> +      items:
>>>> +        - description: PLL id that is expected to enable frequency hopping.
>>>
>>> So the clocks are indices from some specific, yet unnamed
>>> clock-controller? This feels hacky. You should rather take here clock
>>> phandles (1) or integrate it into specific clock controller (2). The
>>> reason is that either your device does something on top of existing
>>> clocks (option 1, thus it takes clock as inputs) or it modifies existing
>>> clocks (option 2, thus it is integral part of clock-controller).
>>>
>>
>> FHCTL is a MCU that handles (some, or all, depending on what's supported on the
>> SoC and what's needed by the board) PLL frequency setting, doing it in steps and
>> avoiding overshooting and other issues.
>>
>> We had a pretty big conversation about this a while ago and the indices instead
>> of phandles is actually my fault, that happened because I initially proposed your
>> option 2 but then for a number of reasons we went with this kind of solution.
>>
>> I know it's going to be a long read, but the entire conversation is on the list [1]
>>
> 
> Sorry, but it's a hacky architecture where one device (which is a clock
> provider) and second device have no relationship in hardware description
> but both play with each other resources.

Yes, that's exactly how it is hardware-side. Except, just to be as clear as
possible, FHCTL plays with the clock provider, but *not* vice-versa.

> That's simply not a proper
> hardware description, so again:
> 
> 1. If this is separate device (as you indicated), then it needs
> expressing the dependencies and uses of other device resources.

Agreed. In this case, what about...

mediatek,hopping-ssc-percents = <&provider CLK_SOMEPLL 3>;

or would it be better to specify the clocks in a separated property?

clocks = <&provider CLK_SOMEPLL>, <&provider CLK_SOME_OTHER_PLL>;
mediatek,hopping-ssc-percents = <3>, <5>;

Thanks,
Angelo

> 
> 2. If this is not a separate device, but integral part of clock
> controller, then it would be fine but then probably should be child of
> that device.
> 
> Best regards,
> Krzysztof
Re: [PATCH 2/4] dt-bindings: arm: mediatek: Add new bindings of MediaTek frequency hopping
Posted by Krzysztof Kozlowski 2 years ago
On 01/09/2022 13:22, AngeloGioacchino Del Regno wrote:
>> That's simply not a proper
>> hardware description, so again:
>>
>> 1. If this is separate device (as you indicated), then it needs
>> expressing the dependencies and uses of other device resources.
> 
> Agreed. In this case, what about...
> 
> mediatek,hopping-ssc-percents = <&provider CLK_SOMEPLL 3>;
> 
> or would it be better to specify the clocks in a separated property?
> 
> clocks = <&provider CLK_SOMEPLL>, <&provider CLK_SOME_OTHER_PLL>;
> mediatek,hopping-ssc-percents = <3>, <5>;
> 

I propose the last one - using standard clocks property and a matching
table.

Best regards,
Krzysztof
Re: [PATCH 2/4] dt-bindings: arm: mediatek: Add new bindings of MediaTek frequency hopping
Posted by AngeloGioacchino Del Regno 2 years ago
Il 01/09/22 12:30, Krzysztof Kozlowski ha scritto:
> On 01/09/2022 13:22, AngeloGioacchino Del Regno wrote:
>>> That's simply not a proper
>>> hardware description, so again:
>>>
>>> 1. If this is separate device (as you indicated), then it needs
>>> expressing the dependencies and uses of other device resources.
>>
>> Agreed. In this case, what about...
>>
>> mediatek,hopping-ssc-percents = <&provider CLK_SOMEPLL 3>;
>>
>> or would it be better to specify the clocks in a separated property?
>>
>> clocks = <&provider CLK_SOMEPLL>, <&provider CLK_SOME_OTHER_PLL>;
>> mediatek,hopping-ssc-percents = <3>, <5>;
>>
> 
> I propose the last one - using standard clocks property and a matching
> table.
> 

Right. I like the last one a bit better, as well.

Thanks for the advices!
Angelo