On Wed, Nov 30, 2016 at 10:44 PM, Rob Herring <robh@xxxxxxxxxx> wrote:
> On Fri, Nov 25, 2016 at 02:01:50PM +0100, Martin Blumenstingl wrote:
>> This allows configuring the RGMII TX clock delay. The RGMII clock is
>> generated by underlying hardware of the the Meson 8b / GXBB DWMAC glue.
>> The configuration depends on the actual hardware (no delay may be
>> needed due to the design of the actual circuit, the PHY might add this
>> delay, etc.).
>>
>> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
>> ---
>> Documentation/devicetree/bindings/net/meson-dwmac.txt | 14 ++++++++++++++
>> 1 file changed, 14 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/net/meson-dwmac.txt b/Documentation/devicetree/bindings/net/meson-dwmac.txt
>> index 89e62dd..f8bc540 100644
>> --- a/Documentation/devicetree/bindings/net/meson-dwmac.txt
>> +++ b/Documentation/devicetree/bindings/net/meson-dwmac.txt
>> @@ -25,6 +25,20 @@ Required properties on Meson8b and newer:
>> - "clkin0" - first parent clock of the internal mux
>> - "clkin1" - second parent clock of the internal mux
>>
>> +Optional properties on Meson8b and newer:
>> +- amlogic,tx-delay-ns: The internal RGMII TX clock delay (provided
>> + by this driver) in nanoseconds. Allowed values
>> + are: 0ns, 2ns, 4ns, 6ns.
>> + This must be configured when the phy-mode is
>> + "rgmii" (typically a value of 2ns is used in
>> + this case).
>> + When phy-mode is set to "rgmii-id" or
>> + "rgmii-txid" the TX clock delay is already
>> + provided by the PHY. In that case this
>> + property should be set to 0ns (which disables
>> + the TX clock delay in the MAC to prevent the
>> + clock from going off because both PHY and MAC
>> + are adding a delay).
>
> What's the default? Why can't no property mean 0ns delay?
This value (2ns) was previously hardcoded. Having a default of 0ns
means that patch 7 ("ARM64: dts: amlogic: add the ethernet TX delay
configuration") becomes mandatory (otherwise we'll have broken Gbit
ethernet again because the TX delay is now disabled in the PHY when
phy-mode is "rgmii" and additionally we don't apply the 2ns TX delay
on the MAC side when the property is missing).
I'm fine with either way though - just let me know so I can adjust the
code accordingly.
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