Document the FS Differential TX Output Resistance Tuning value found on
the eUSB2 repeater on Qualcomm PMICs.
Signed-off-by: Luca Weiss <luca.weiss@fairphone.com>
---
Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml b/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml
index 27f064a71c9fb8cb60e8333fb285f0510a4af94f..6bfd11657e2992735998063b3ca390e04a03930d 100644
--- a/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml
+++ b/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml
@@ -52,6 +52,12 @@ properties:
minimum: 0
maximum: 7
+ qcom,tune-res-fsdif:
+ $ref: /schemas/types.yaml#/definitions/uint8
+ description: FS Differential TX Output Resistance Tuning
+ minimum: 0
+ maximum: 7
+
required:
- compatible
- reg
--
2.50.0On Wed, Jun 25, 2025 at 11:14:56AM +0200, Luca Weiss wrote: > Document the FS Differential TX Output Resistance Tuning value found on > the eUSB2 repeater on Qualcomm PMICs. > > Signed-off-by: Luca Weiss <luca.weiss@fairphone.com> > --- > Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml b/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml > index 27f064a71c9fb8cb60e8333fb285f0510a4af94f..6bfd11657e2992735998063b3ca390e04a03930d 100644 > --- a/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml > +++ b/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml > @@ -52,6 +52,12 @@ properties: > minimum: 0 > maximum: 7 > > + qcom,tune-res-fsdif: > + $ref: /schemas/types.yaml#/definitions/uint8 > + description: FS Differential TX Output Resistance Tuning Resistance is in Ohms, tuning could be in dB, so I wonder what are the actual units here. Neither commit msg nor this description helps me to understand that. Best regards, Krzysztof
On Tue, Jul 08, 2025 at 10:13:24AM +0200, Krzysztof Kozlowski wrote: > On Wed, Jun 25, 2025 at 11:14:56AM +0200, Luca Weiss wrote: > > Document the FS Differential TX Output Resistance Tuning value found on > > the eUSB2 repeater on Qualcomm PMICs. > > > > Signed-off-by: Luca Weiss <luca.weiss@fairphone.com> > > --- > > Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml | 6 ++++++ > > 1 file changed, 6 insertions(+) > > > > diff --git a/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml b/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml > > index 27f064a71c9fb8cb60e8333fb285f0510a4af94f..6bfd11657e2992735998063b3ca390e04a03930d 100644 > > --- a/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml > > +++ b/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml > > @@ -52,6 +52,12 @@ properties: > > minimum: 0 > > maximum: 7 > > > > + qcom,tune-res-fsdif: > > + $ref: /schemas/types.yaml#/definitions/uint8 > > + description: FS Differential TX Output Resistance Tuning > > Resistance is in Ohms, tuning could be in dB, so I wonder what are the > actual units here. Neither commit msg nor this description helps me to > understand that. I checked and the values are in Ohms. Best regards, Krzysztof
On Tue Jul 8, 2025 at 10:21 AM CEST, Krzysztof Kozlowski wrote: > On Tue, Jul 08, 2025 at 10:13:24AM +0200, Krzysztof Kozlowski wrote: >> On Wed, Jun 25, 2025 at 11:14:56AM +0200, Luca Weiss wrote: >> > Document the FS Differential TX Output Resistance Tuning value found on >> > the eUSB2 repeater on Qualcomm PMICs. >> > >> > Signed-off-by: Luca Weiss <luca.weiss@fairphone.com> >> > --- >> > Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml | 6 ++++++ >> > 1 file changed, 6 insertions(+) >> > >> > diff --git a/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml b/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml >> > index 27f064a71c9fb8cb60e8333fb285f0510a4af94f..6bfd11657e2992735998063b3ca390e04a03930d 100644 >> > --- a/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml >> > +++ b/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml >> > @@ -52,6 +52,12 @@ properties: >> > minimum: 0 >> > maximum: 7 >> > >> > + qcom,tune-res-fsdif: >> > + $ref: /schemas/types.yaml#/definitions/uint8 >> > + description: FS Differential TX Output Resistance Tuning >> >> Resistance is in Ohms, tuning could be in dB, so I wonder what are the >> actual units here. Neither commit msg nor this description helps me to >> understand that. > > I checked and the values are in Ohms. Yes it's Ohms but not 0x00 = 0 ohms, and it's also an offset in ohms from the nominal value according to the Hardware Register Description I have, e.g. 0x7 = -12.1ohm from the default I can try and create bindings using these Ohm offset values, I didn't worry about it too much since the other tuning values in these bindings are also just register values, presumably from before Konrad had access to the docs. Regards Luca > > Best regards, > Krzysztof
Hi Krzysztof, On Tue Jul 8, 2025 at 10:31 AM CEST, Luca Weiss wrote: > On Tue Jul 8, 2025 at 10:21 AM CEST, Krzysztof Kozlowski wrote: >> On Tue, Jul 08, 2025 at 10:13:24AM +0200, Krzysztof Kozlowski wrote: >>> On Wed, Jun 25, 2025 at 11:14:56AM +0200, Luca Weiss wrote: >>> > Document the FS Differential TX Output Resistance Tuning value found on >>> > the eUSB2 repeater on Qualcomm PMICs. >>> > >>> > Signed-off-by: Luca Weiss <luca.weiss@fairphone.com> >>> > --- >>> > Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml | 6 ++++++ >>> > 1 file changed, 6 insertions(+) >>> > >>> > diff --git a/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml b/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml >>> > index 27f064a71c9fb8cb60e8333fb285f0510a4af94f..6bfd11657e2992735998063b3ca390e04a03930d 100644 >>> > --- a/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml >>> > +++ b/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml >>> > @@ -52,6 +52,12 @@ properties: >>> > minimum: 0 >>> > maximum: 7 >>> > >>> > + qcom,tune-res-fsdif: >>> > + $ref: /schemas/types.yaml#/definitions/uint8 >>> > + description: FS Differential TX Output Resistance Tuning >>> >>> Resistance is in Ohms, tuning could be in dB, so I wonder what are the >>> actual units here. Neither commit msg nor this description helps me to >>> understand that. >> >> I checked and the values are in Ohms. > > Yes it's Ohms but not 0x00 = 0 ohms, and it's also an offset in ohms > from the nominal value according to the Hardware Register Description I > have, e.g. 0x7 = -12.1ohm from the default > > I can try and create bindings using these Ohm offset values, I didn't > worry about it too much since the other tuning values in these bindings > are also just register values, presumably from before Konrad had access > to the docs. I've taken some more looks, and checked how similar tuning is handled in qcom,usb-snps-femto-v2.yaml and phy-qcom-snps-femto-v2.c, and changing up the concept of tuning in the eUSB2-repeater bindings+driver is not a trivial task. Since this is adding just one more property in-line with the already supported properties in the bindings+driver, can we get this in as-is, and deprecate all 4 qcom,tune-* properties later with a replacement that describes the values better? We have enough people at Qualcomm by now that should be able to do that, and have the required resources to answer any potential questions. Regards Luca
On 09/07/2025 11:40, Luca Weiss wrote: > Hi Krzysztof, > > On Tue Jul 8, 2025 at 10:31 AM CEST, Luca Weiss wrote: >> On Tue Jul 8, 2025 at 10:21 AM CEST, Krzysztof Kozlowski wrote: >>> On Tue, Jul 08, 2025 at 10:13:24AM +0200, Krzysztof Kozlowski wrote: >>>> On Wed, Jun 25, 2025 at 11:14:56AM +0200, Luca Weiss wrote: >>>>> Document the FS Differential TX Output Resistance Tuning value found on >>>>> the eUSB2 repeater on Qualcomm PMICs. >>>>> >>>>> Signed-off-by: Luca Weiss <luca.weiss@fairphone.com> >>>>> --- >>>>> Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml | 6 ++++++ >>>>> 1 file changed, 6 insertions(+) >>>>> >>>>> diff --git a/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml b/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml >>>>> index 27f064a71c9fb8cb60e8333fb285f0510a4af94f..6bfd11657e2992735998063b3ca390e04a03930d 100644 >>>>> --- a/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml >>>>> +++ b/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml >>>>> @@ -52,6 +52,12 @@ properties: >>>>> minimum: 0 >>>>> maximum: 7 >>>>> >>>>> + qcom,tune-res-fsdif: >>>>> + $ref: /schemas/types.yaml#/definitions/uint8 >>>>> + description: FS Differential TX Output Resistance Tuning >>>> >>>> Resistance is in Ohms, tuning could be in dB, so I wonder what are the >>>> actual units here. Neither commit msg nor this description helps me to >>>> understand that. >>> >>> I checked and the values are in Ohms. >> >> Yes it's Ohms but not 0x00 = 0 ohms, and it's also an offset in ohms >> from the nominal value according to the Hardware Register Description I >> have, e.g. 0x7 = -12.1ohm from the default >> >> I can try and create bindings using these Ohm offset values, I didn't >> worry about it too much since the other tuning values in these bindings >> are also just register values, presumably from before Konrad had access >> to the docs. > > I've taken some more looks, and checked how similar tuning is handled in > qcom,usb-snps-femto-v2.yaml and phy-qcom-snps-femto-v2.c, and changing up > the concept of tuning in the eUSB2-repeater bindings+driver is not a > trivial task. > > Since this is adding just one more property in-line with the already > supported properties in the bindings+driver, can we get this in as-is, > and deprecate all 4 qcom,tune-* properties later with a replacement that > describes the values better? This is a new property, so other existing properties do not matter here. We cannot take new code which you already think should be deprecated. register-like values are acceptable for vendor properties, but that does not make them usually more readable. The question is whether this should be more readable for hardware engineers or anyone writing/validating DTS. Is the actual resistance important or no one ever cares because you paste whatever qcom told you and you do not know what should be actually there? I can imagine the first - that some document explains you should have resistance of foo because of bar, which would mean the property should be more readable. But I can also imagine the second. Make your claim in commit msg. > We have enough people at Qualcomm by now that should be able to do that, > and have the required resources to answer any potential questions. They are busy sending vendor/downstream tree patches... Best regards, Krzysztof
On Wed Jul 9, 2025 at 12:16 PM CEST, Krzysztof Kozlowski wrote: > On 09/07/2025 11:40, Luca Weiss wrote: >> Hi Krzysztof, >> >> On Tue Jul 8, 2025 at 10:31 AM CEST, Luca Weiss wrote: >>> On Tue Jul 8, 2025 at 10:21 AM CEST, Krzysztof Kozlowski wrote: >>>> On Tue, Jul 08, 2025 at 10:13:24AM +0200, Krzysztof Kozlowski wrote: >>>>> On Wed, Jun 25, 2025 at 11:14:56AM +0200, Luca Weiss wrote: >>>>>> Document the FS Differential TX Output Resistance Tuning value found on >>>>>> the eUSB2 repeater on Qualcomm PMICs. >>>>>> >>>>>> Signed-off-by: Luca Weiss <luca.weiss@fairphone.com> >>>>>> --- >>>>>> Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml | 6 ++++++ >>>>>> 1 file changed, 6 insertions(+) >>>>>> >>>>>> diff --git a/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml b/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml >>>>>> index 27f064a71c9fb8cb60e8333fb285f0510a4af94f..6bfd11657e2992735998063b3ca390e04a03930d 100644 >>>>>> --- a/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml >>>>>> +++ b/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml >>>>>> @@ -52,6 +52,12 @@ properties: >>>>>> minimum: 0 >>>>>> maximum: 7 >>>>>> >>>>>> + qcom,tune-res-fsdif: >>>>>> + $ref: /schemas/types.yaml#/definitions/uint8 >>>>>> + description: FS Differential TX Output Resistance Tuning >>>>> >>>>> Resistance is in Ohms, tuning could be in dB, so I wonder what are the >>>>> actual units here. Neither commit msg nor this description helps me to >>>>> understand that. >>>> >>>> I checked and the values are in Ohms. >>> >>> Yes it's Ohms but not 0x00 = 0 ohms, and it's also an offset in ohms >>> from the nominal value according to the Hardware Register Description I >>> have, e.g. 0x7 = -12.1ohm from the default >>> >>> I can try and create bindings using these Ohm offset values, I didn't >>> worry about it too much since the other tuning values in these bindings >>> are also just register values, presumably from before Konrad had access >>> to the docs. >> >> I've taken some more looks, and checked how similar tuning is handled in >> qcom,usb-snps-femto-v2.yaml and phy-qcom-snps-femto-v2.c, and changing up >> the concept of tuning in the eUSB2-repeater bindings+driver is not a >> trivial task. >> >> Since this is adding just one more property in-line with the already >> supported properties in the bindings+driver, can we get this in as-is, >> and deprecate all 4 qcom,tune-* properties later with a replacement that >> describes the values better? > > This is a new property, so other existing properties do not matter here. > We cannot take new code which you already think should be deprecated. > > register-like values are acceptable for vendor properties, but that does > not make them usually more readable. The question is whether this should > be more readable for hardware engineers or anyone writing/validating > DTS. Is the actual resistance important or no one ever cares because you > paste whatever qcom told you and you do not know what should be actually > there? > > I can imagine the first - that some document explains you should have > resistance of foo because of bar, which would mean the property should > be more readable. But I can also imagine the second. Make your claim in > commit msg. Would this text in the commit message work for you? --- Document the FS Differential TX Output Resistance Tuning value found on the eUSB2 repeater on Qualcomm PMICs. The tuning values have special meanings, being different offsets of the resistance to the default value in Ohms but the exact meaning is not relevant here, as the correct tuning is determined by hardware engineers to make sure the electrical properties are as expected. --- I'm trying to avoid resending the whole series if we're not yet aligned on the wording. Regards Luca > >> We have enough people at Qualcomm by now that should be able to do that, >> and have the required resources to answer any potential questions. > They are busy sending vendor/downstream tree patches... > > Best regards, > Krzysztof
On 09/07/2025 14:22, Luca Weiss wrote: > On Wed Jul 9, 2025 at 12:16 PM CEST, Krzysztof Kozlowski wrote: >> On 09/07/2025 11:40, Luca Weiss wrote: >>> Hi Krzysztof, >>> >>> On Tue Jul 8, 2025 at 10:31 AM CEST, Luca Weiss wrote: >>>> On Tue Jul 8, 2025 at 10:21 AM CEST, Krzysztof Kozlowski wrote: >>>>> On Tue, Jul 08, 2025 at 10:13:24AM +0200, Krzysztof Kozlowski wrote: >>>>>> On Wed, Jun 25, 2025 at 11:14:56AM +0200, Luca Weiss wrote: >>>>>>> Document the FS Differential TX Output Resistance Tuning value found on >>>>>>> the eUSB2 repeater on Qualcomm PMICs. >>>>>>> >>>>>>> Signed-off-by: Luca Weiss <luca.weiss@fairphone.com> >>>>>>> --- >>>>>>> Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml | 6 ++++++ >>>>>>> 1 file changed, 6 insertions(+) >>>>>>> >>>>>>> diff --git a/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml b/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml >>>>>>> index 27f064a71c9fb8cb60e8333fb285f0510a4af94f..6bfd11657e2992735998063b3ca390e04a03930d 100644 >>>>>>> --- a/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml >>>>>>> +++ b/Documentation/devicetree/bindings/phy/qcom,snps-eusb2-repeater.yaml >>>>>>> @@ -52,6 +52,12 @@ properties: >>>>>>> minimum: 0 >>>>>>> maximum: 7 >>>>>>> >>>>>>> + qcom,tune-res-fsdif: >>>>>>> + $ref: /schemas/types.yaml#/definitions/uint8 >>>>>>> + description: FS Differential TX Output Resistance Tuning >>>>>> >>>>>> Resistance is in Ohms, tuning could be in dB, so I wonder what are the >>>>>> actual units here. Neither commit msg nor this description helps me to >>>>>> understand that. >>>>> >>>>> I checked and the values are in Ohms. >>>> >>>> Yes it's Ohms but not 0x00 = 0 ohms, and it's also an offset in ohms >>>> from the nominal value according to the Hardware Register Description I >>>> have, e.g. 0x7 = -12.1ohm from the default >>>> >>>> I can try and create bindings using these Ohm offset values, I didn't >>>> worry about it too much since the other tuning values in these bindings >>>> are also just register values, presumably from before Konrad had access >>>> to the docs. >>> >>> I've taken some more looks, and checked how similar tuning is handled in >>> qcom,usb-snps-femto-v2.yaml and phy-qcom-snps-femto-v2.c, and changing up >>> the concept of tuning in the eUSB2-repeater bindings+driver is not a >>> trivial task. >>> >>> Since this is adding just one more property in-line with the already >>> supported properties in the bindings+driver, can we get this in as-is, >>> and deprecate all 4 qcom,tune-* properties later with a replacement that >>> describes the values better? >> >> This is a new property, so other existing properties do not matter here. >> We cannot take new code which you already think should be deprecated. >> >> register-like values are acceptable for vendor properties, but that does >> not make them usually more readable. The question is whether this should >> be more readable for hardware engineers or anyone writing/validating >> DTS. Is the actual resistance important or no one ever cares because you >> paste whatever qcom told you and you do not know what should be actually >> there? >> >> I can imagine the first - that some document explains you should have >> resistance of foo because of bar, which would mean the property should >> be more readable. But I can also imagine the second. Make your claim in >> commit msg. > > Would this text in the commit message work for you? > > --- > Document the FS Differential TX Output Resistance Tuning value found on > the eUSB2 repeater on Qualcomm PMICs. The tuning values have special > meanings, being different offsets of the resistance to the default value > in Ohms but the exact meaning is not relevant here, as the correct > tuning is determined by hardware engineers to make sure the electrical > properties are as expected. > --- > > I'm trying to avoid resending the whole series if we're not yet aligned > on the wording. Sounds fine. Best regards, Krzysztof
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