PHY doesn't receive the first packet #164
Description
XK_ETH_XU316_DUAL_100M uses the TI DP83826 PHY. During testing we noticed that very occasionally (1% of the time) the first packet sent after initialisation may be dropped for certain link partners. Subsequent packets are always OK. This is consistent with a similar bug seen on the TI forum <https://e2e.ti.com/support/interface-group/interface/f/interface-forum/956808/dp83822i-after-link-up-first-packet-is-not-being-transmitted>_.
For most applications this is not an issue however for test cases it may be worth noting.
Sending an initial dummy Tx packet from the application after link up works around this issue.
However, this doesn't work for test_hw_hot_plug, which tests device hot plugging by getting the link to go down multiple times while the application only sends a dummy packet at init time after seeing link up for the first time. This test works around this issue by requesting the application to send a packet after every link back up instance and ignoring whether its received or not, before requesting the actual transfer of packets that we care about.