Messages in this thread | | | Date | Tue, 12 Oct 2021 09:48:46 +0200 | From | Michael Walle <> | Subject | Re: [PATCH v2 1/2] dt-bindings: mtd: spi-nor: Add output-driver-strength property |
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Am 2021-10-12 08:17, schrieb Alexander Stein: > This property is for optimizing output voltage impedance and is > specific to each board. It overwrites the default set by the flash > device. Various flash devices support different impedances. > > Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com> > --- > Changes in v2: > * Updated the property description and the commit message accordingly > > Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml > b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml > index ed590d7c6e37..4c3c506a8853 100644 > --- a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml > +++ b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml > @@ -72,6 +72,14 @@ properties: > be used on such systems, to denote the absence of a reliable > reset > mechanism. > > + output-driver-strength: > + $ref: /schemas/types.yaml#/definitions/uint32 > + description: > + Output driver strength in ohms which optimizes the impedance at > Vcc/2 > + output voltage. This property overwrites the default set by the > flash > + device. This is board specific and should be determined by the > + manufacturer. Various flash devices support different > impedances.
Mh, this seems to be very tailored to this flash chip. Eg. the "Vcc/2", is this something specific to this flash or is this some kind of common usage? For example, Winbond flashes specifies the output driver strength in percent. Settings are 25%, 50%, 75%, 100% there.
I'd have to ask a hardware guy, if one could convert between these two representations of the driver strength.
Rob, do you know how is this case ususally handled? Can there be different properties, like:
output-driver-strength-ohms output-driver-strength-percent
or similar.
-michael
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