| Message ID | 20210106173900.388758-1-aford173@gmail.com (mailing list archive) |
|---|---|
| State | RFC, archived |
| Headers | show |
| Series | [RFC,1/2] dt-bindings: clk: versaclock5: Add load capacitance properties | expand |
Hi Adam, On 06/01/21 18:38, Adam Ford wrote: > There are two registers which can set the load capacitance for > XTAL1 and XTAL2. These are optional registers when using an > external crystal. Update the bindings to support them. > > Signed-off-by: Adam Ford <aford173@gmail.com> > --- > .../devicetree/bindings/clock/idt,versaclock5.yaml | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml b/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml > index 2ac1131fd922..e5e55ffb266e 100644 > --- a/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml > +++ b/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml > @@ -59,6 +59,18 @@ properties: > minItems: 1 > maxItems: 2 > > + idt,xtal1-load-femtofarads: I wonder whether we should have a common, vendor independent property. In mainline we have xtal-load-pf (ti,cdce925.txt bindings) which has no vendor prefix. However I don't know how much common it is to need different loads for x1 and x2. Any hardware engineer around? > + $ref: /schemas/types.yaml#/definitions/uint32 > + minimum: 9000 > + maximum: 25000 > + description: Optional loading capacitor for XTAL1 Nit: I think the common wording is "load capacitor", not "loading capacitor".
On Fri, Jan 8, 2021 at 4:49 PM Luca Ceresoli <luca@lucaceresoli.net> wrote: > > Hi Adam, > > On 06/01/21 18:38, Adam Ford wrote: > > There are two registers which can set the load capacitance for > > XTAL1 and XTAL2. These are optional registers when using an > > external crystal. Update the bindings to support them. > > > > Signed-off-by: Adam Ford <aford173@gmail.com> > > --- > > .../devicetree/bindings/clock/idt,versaclock5.yaml | 12 ++++++++++++ > > 1 file changed, 12 insertions(+) > > > > diff --git a/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml b/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml > > index 2ac1131fd922..e5e55ffb266e 100644 > > --- a/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml > > +++ b/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml > > @@ -59,6 +59,18 @@ properties: > > minItems: 1 > > maxItems: 2 > > > > + idt,xtal1-load-femtofarads: > > I wonder whether we should have a common, vendor independent property. That would be nice. > In mainline we have xtal-load-pf (ti,cdce925.txt bindings) which has no > vendor prefix. However I don't know how much common it is to need rtc-pcf85063.c uses quartz-load-femtofarads, so there is already some discrepancy. Since the unit of measure here is femtofarads, using pF in the name seems wrong. We need to read the data as a u32, so femtofarads works better than pF, which would require a decimal point. > different loads for x1 and x2. Any hardware engineer around? I talked to a hardware engineer where I work, and he said it makes sense to keep them the same. I only separated them because there are two registers, and I assumed there might be a reason to have X1 and X2 be different, but I'm ok with reading one value and writing it to two different registers. adam > > > + $ref: /schemas/types.yaml#/definitions/uint32 > > + minimum: 9000 > > + maximum: 25000 > > + description: Optional loading capacitor for XTAL1 > > Nit: I think the common wording is "load capacitor", not "loading > capacitor". > > -- > Luca
On Wed, Jan 06, 2021 at 11:38:59AM -0600, Adam Ford wrote: > There are two registers which can set the load capacitance for > XTAL1 and XTAL2. These are optional registers when using an > external crystal. Update the bindings to support them. > > Signed-off-by: Adam Ford <aford173@gmail.com> > --- > .../devicetree/bindings/clock/idt,versaclock5.yaml | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml b/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml > index 2ac1131fd922..e5e55ffb266e 100644 > --- a/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml > +++ b/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml > @@ -59,6 +59,18 @@ properties: > minItems: 1 > maxItems: 2 > > + idt,xtal1-load-femtofarads: > + $ref: /schemas/types.yaml#/definitions/uint32 Already has a type, so you can drop the $ref. > + minimum: 9000 > + maximum: 25000 > + description: Optional loading capacitor for XTAL1 > + > + idt,xtal2-load-femtofarads: > + $ref: /schemas/types.yaml#/definitions/uint32 > + minimum: 9000 > + maximum: 25000 > + description: Optional loading capacitor for XTAL2 > + > patternProperties: > "^OUT[1-4]$": > type: object > -- > 2.25.1 >
On Tue, Jan 12, 2021 at 9:16 PM Rob Herring <robh@kernel.org> wrote: > > On Wed, Jan 06, 2021 at 11:38:59AM -0600, Adam Ford wrote: > > There are two registers which can set the load capacitance for > > XTAL1 and XTAL2. These are optional registers when using an > > external crystal. Update the bindings to support them. > > > > Signed-off-by: Adam Ford <aford173@gmail.com> > > --- > > .../devicetree/bindings/clock/idt,versaclock5.yaml | 12 ++++++++++++ > > 1 file changed, 12 insertions(+) > > > > diff --git a/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml b/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml > > index 2ac1131fd922..e5e55ffb266e 100644 > > --- a/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml > > +++ b/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml > > @@ -59,6 +59,18 @@ properties: > > minItems: 1 > > maxItems: 2 > > > > + idt,xtal1-load-femtofarads: > > + $ref: /schemas/types.yaml#/definitions/uint32 > > Already has a type, so you can drop the $ref. > > > + minimum: 9000 > > + maximum: 25000 Luca, Do you want the range to the 9000 - 25000 per the datasheet, or should I use the max value based on the programmer guide? Currently, my intent was to cap the value to 11111b, so anyone who writes 23000, 24000, or 25000 will all be the same value based on the feedback I got from Renesas. adam > > + description: Optional loading capacitor for XTAL1 > > + > > + idt,xtal2-load-femtofarads: > > + $ref: /schemas/types.yaml#/definitions/uint32 > > + minimum: 9000 > > + maximum: 25000 > > + description: Optional loading capacitor for XTAL2 > > + > > patternProperties: > > "^OUT[1-4]$": > > type: object > > -- > > 2.25.1 > >
Hi Adam, On 13/01/21 13:31, Adam Ford wrote: > On Tue, Jan 12, 2021 at 9:16 PM Rob Herring <robh@kernel.org> wrote: >> >> On Wed, Jan 06, 2021 at 11:38:59AM -0600, Adam Ford wrote: >>> There are two registers which can set the load capacitance for >>> XTAL1 and XTAL2. These are optional registers when using an >>> external crystal. Update the bindings to support them. >>> >>> Signed-off-by: Adam Ford <aford173@gmail.com> >>> --- >>> .../devicetree/bindings/clock/idt,versaclock5.yaml | 12 ++++++++++++ >>> 1 file changed, 12 insertions(+) >>> >>> diff --git a/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml b/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml >>> index 2ac1131fd922..e5e55ffb266e 100644 >>> --- a/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml >>> +++ b/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml >>> @@ -59,6 +59,18 @@ properties: >>> minItems: 1 >>> maxItems: 2 >>> >>> + idt,xtal1-load-femtofarads: >>> + $ref: /schemas/types.yaml#/definitions/uint32 >> >> Already has a type, so you can drop the $ref. >> >>> + minimum: 9000 >>> + maximum: 25000 > > Luca, > > Do you want the range to the 9000 - 25000 per the datasheet, or should > I use the max value based on the programmer guide? Currently, my > intent was to cap the value to 11111b, so anyone who writes 23000, > 24000, or 25000 will all be the same value based on the feedback I got > from Renesas. DT should describe the HW, so I'd use the same range that can be set in hardware, regardless of driver support. Thus it should be: 9000 - [9000 + 430 * 32] = 9000 - 22760
Hi Adam, On 09/01/21 03:48, Adam Ford wrote: > On Fri, Jan 8, 2021 at 4:49 PM Luca Ceresoli <luca@lucaceresoli.net> wrote: >> >> Hi Adam, >> >> On 06/01/21 18:38, Adam Ford wrote: >>> There are two registers which can set the load capacitance for >>> XTAL1 and XTAL2. These are optional registers when using an >>> external crystal. Update the bindings to support them. >>> >>> Signed-off-by: Adam Ford <aford173@gmail.com> >>> --- >>> .../devicetree/bindings/clock/idt,versaclock5.yaml | 12 ++++++++++++ >>> 1 file changed, 12 insertions(+) >>> >>> diff --git a/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml b/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml >>> index 2ac1131fd922..e5e55ffb266e 100644 >>> --- a/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml >>> +++ b/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml >>> @@ -59,6 +59,18 @@ properties: >>> minItems: 1 >>> maxItems: 2 >>> >>> + idt,xtal1-load-femtofarads: >> >> I wonder whether we should have a common, vendor independent property. > > That would be nice. > >> In mainline we have xtal-load-pf (ti,cdce925.txt bindings) which has no >> vendor prefix. However I don't know how much common it is to need > > rtc-pcf85063.c uses quartz-load-femtofarads, so there is already some > discrepancy. > > Since the unit of measure here is femtofarads, using pF in the name seems wrong. > We need to read the data as a u32, so femtofarads works better than > pF, which would require a decimal point. > >> different loads for x1 and x2. Any hardware engineer around? > > I talked to a hardware engineer where I work, and he said it makes > sense to keep them the same. I only separated them because there are > two registers, and I assumed there might be a reason to have X1 and X2 > be different, but I'm ok with reading one value and writing it to two > different registers. If both your HW engineer and the Renesas docs say setting different values is not useful in real life, and other drivers don't set different values as well, it looks like that is the reasonable way. I think it also increases likelihood of establishing a unique property name to be used for all future chips.
diff --git a/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml b/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml index 2ac1131fd922..e5e55ffb266e 100644 --- a/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml +++ b/Documentation/devicetree/bindings/clock/idt,versaclock5.yaml @@ -59,6 +59,18 @@ properties: minItems: 1 maxItems: 2 + idt,xtal1-load-femtofarads: + $ref: /schemas/types.yaml#/definitions/uint32 + minimum: 9000 + maximum: 25000 + description: Optional loading capacitor for XTAL1 + + idt,xtal2-load-femtofarads: + $ref: /schemas/types.yaml#/definitions/uint32 + minimum: 9000 + maximum: 25000 + description: Optional loading capacitor for XTAL2 + patternProperties: "^OUT[1-4]$": type: object
There are two registers which can set the load capacitance for XTAL1 and XTAL2. These are optional registers when using an external crystal. Update the bindings to support them. Signed-off-by: Adam Ford <aford173@gmail.com> --- .../devicetree/bindings/clock/idt,versaclock5.yaml | 12 ++++++++++++ 1 file changed, 12 insertions(+)