Merge branch 'regulator-5.4' into regulator-linus

[sfrench/cifs-2.6.git] / Documentation / devicetree / bindings / net / micrel-ksz90x1.txt

diff --git a/Documentation/devicetree/bindings/net/micrel-ksz90x1.txt b/Documentation/devicetree/bindings/net/micrel-ksz90x1.txt
index 5100358177c98127c169b046393cffda0f23dec6..b921731cd970e35a9221cae0f33fb982209949df 100644 (file)
--- a/Documentation/devicetree/bindings/net/micrel-ksz90x1.txt
+++ b/Documentation/devicetree/bindings/net/micrel-ksz90x1.txt
@@ -12,8 +12,36 @@ and therefore may overwrite them.
 KSZ9021:
 
   All skew control options are specified in picoseconds. The minimum
-  value is 0, the maximum value is 3000, and it is incremented by 200ps
-  steps.
+  value is 0, the maximum value is 3000, and it can be specified in 200ps
+  steps, *but* these values are in not fact what you get because this chip's
+  skew values actually increase in 120ps steps, starting from -840ps. The
+  incorrect values came from an error in the original KSZ9021 datasheet
+  before it was corrected in revision 1.2 (Feb 2014), but it is too late to
+  change the driver now because of the many existing device trees that have
+  been created using values that go up in increments of 200.
+
+  The following table shows the actual skew delay you will get for each of the
+  possible devicetree values, and the number that will be programmed into the
+  corresponding pad skew register:
+
+  Device Tree Value    Delay   Pad Skew Register Value
+  -----------------------------------------------------
+       0               -840ps          0000
+       200             -720ps          0001
+       400             -600ps          0010
+       600             -480ps          0011
+       800             -360ps          0100
+       1000            -240ps          0101
+       1200            -120ps          0110
+       1400               0ps          0111
+       1600             120ps          1000
+       1800             240ps          1001
+       2000             360ps          1010
+       2200             480ps          1011
+       2400             600ps          1100
+       2600             720ps          1101
+       2800             840ps          1110
+       3000             960ps          1111
 
   Optional properties: