Fixed-link Feature

这种特性主要是为了解决没有使用mdio进行管理的Phy设备。

首先是设备树，内核，以及内核配置三块。

第一：

设备树：

有两种写法，据测试现在都是可行的：

之前是这种写法，

A 'fixed-link' property in the Ethernet MAC node, with 5 cells, of the form <a b c d e> with the following accepted values:

- a: emulated PHY ID, choose any but but unique to the all specified fixed-links, from 0 to 31

- b: duplex configuration: 0 for half duplex, 1 for full duplex

- c: link speed in Mbits/sec, accepted values are: 10, 100 and 1000

- d: pause configuration: 0 for no pause, 1 for pause

- e: asymmetric pause configuration: 0 for no asymmetric pause, 1 for asymmetric pause

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A 'fixed-link' sub-node of the Ethernet MAC device node, with the followingproperties:

* 'speed' (integer, mandatory), to indicate the link speed. Accepted values are 10, 100 and 1000

* 'full-duplex' (boolean, optional), to indicate that full duplex is used. When absent, half duplex is assumed.

* 'pause' (boolean, optional), to indicate that pause should be enabled.

* 'asym-pause' (boolean, optional), to indicate that asym_pause should be enabled.

* 'link-gpios' ('gpio-list', optional), to indicate if a gpio can be read to determine if the link is up.

https://alteraforum.com/forum/attachment.php?attachmentid=14009&stc=1

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