stmmac mitigation and ethtool coalesce parameters

[Giuseppe CAVALLARO <peppe.cavallaro@st.com>]

Hello
I'm reworking the mitigation schema in the stmmac and removing the old
and dead STMMAC_TIMER code.

On new chips we have an HW RX-Watchdog that can be used for mitigating
the Rx-interrupts and first results look promising.

Before posting the patches I have a doubt about the ethtool coalesce
parameters to use in the driver to tune the following parameters:

- On Rx-side I have:
  a parameter that is the RI Watchdog Timer count. It indicates the
  number of system clock cycles.

- On Tx-side, the mitigation schema I'm using is based on a SW timer
  that calls the tx function (stmmac_tx) to reclaim the resource after
  transmitting the frames.
  Also there is another parameter (like a threshold) used to program
  the descriptors avoiding to set the interrupt on completion bit in
  when the frame is sent (xmit). This means that the stmmac_tx can be
  called by the ISR too.   This approach is showing really good figures
  as well.

so I wonder which are the appropriate ethtool coalesce parameters to
use? Or could I tune them by using sysfs entries?

Welcome advice.

Peppe