diff mbox series

[v2,1/2] dt-bindings: mtd: spi-nor: Add output-driver-strength property

Message ID 20211012061704.284214-1-alexander.stein@ew.tq-group.com
State Under Review
Delegated to: Ambarus Tudor
Headers show
Series [v2,1/2] dt-bindings: mtd: spi-nor: Add output-driver-strength property | expand

Commit Message

Alexander Stein Oct. 12, 2021, 6:17 a.m. UTC
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(+)

Comments

Michael Walle Oct. 12, 2021, 7:48 a.m. UTC | #1
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
diff mbox series

Patch

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.
+
   label: true
 
   partitions: