| Message ID | 1475676188-10639-1-git-send-email-mike.looijmans@topic.nl |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
On 10/05/2016 07:03 AM, Mike Looijmans wrote: > The KSZ9031 skew registers contain an offset, the chip's default value > is "neutral" which does not add any skew. Programming a 0 into a skew > property will actually set it the maximal negative adjustment and not > to a neutral position as one would expect. > > Explain this situation in the devicetree binding documentation and list > the settings that the chip considers neutral. > > Changing the implementation to accept negative values would have been > a better solution, but would break existing configurations. > > Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl> Reviewed-by: Florian Fainelli <f.fainelli@gmail.com> Thanks!
From: Mike Looijmans <mike.looijmans@topic.nl> Date: Wed, 5 Oct 2016 16:03:08 +0200 > The KSZ9031 skew registers contain an offset, the chip's default value > is "neutral" which does not add any skew. Programming a 0 into a skew > property will actually set it the maximal negative adjustment and not > to a neutral position as one would expect. > > Explain this situation in the devicetree binding documentation and list > the settings that the chip considers neutral. > > Changing the implementation to accept negative values would have been > a better solution, but would break existing configurations. > > Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl> Applied.
diff --git a/Documentation/devicetree/bindings/net/micrel-ksz90x1.txt b/Documentation/devicetree/bindings/net/micrel-ksz90x1.txt index f9c32ad..c35b5b4 100644 --- a/Documentation/devicetree/bindings/net/micrel-ksz90x1.txt +++ b/Documentation/devicetree/bindings/net/micrel-ksz90x1.txt @@ -34,16 +34,17 @@ KSZ9031: All skew control options are specified in picoseconds. The minimum value is 0, and the maximum is property-dependent. The increment - step is 60ps. + step is 60ps. The default value is the neutral setting, so setting + rxc-skew-ps=<0> actually results in -900 picoseconds adjustment. Optional properties: - Maximum value of 1860: + Maximum value of 1860, default value 900: - rxc-skew-ps : Skew control of RX clock pad - txc-skew-ps : Skew control of TX clock pad - Maximum value of 900: + Maximum value of 900, default value 420: - rxdv-skew-ps : Skew control of RX CTL pad - txen-skew-ps : Skew control of TX CTL pad
The KSZ9031 skew registers contain an offset, the chip's default value is "neutral" which does not add any skew. Programming a 0 into a skew property will actually set it the maximal negative adjustment and not to a neutral position as one would expect. Explain this situation in the devicetree binding documentation and list the settings that the chip considers neutral. Changing the implementation to accept negative values would have been a better solution, but would break existing configurations. Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl> --- Documentation/devicetree/bindings/net/micrel-ksz90x1.txt | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)