Às 2:10 PM de 4/12/2017, Andrew Lunn escreveu: >>>> +- snps,drop-tx-status: this enables drop tx status >>> >>> Hi Joao >>> >>> Was the conclusion from testing that this cannot be turned on by >>> default? >> >> This feature is great for applications that need good performance, but has a >> drawback since it has an impact in timestamp feature in Tx. There are some >> operations in PTP where the timestamp is given to the host through the TX >> status >> in the descriptor, so this will have an impact. >> >> There's a way of solving this of course by making the driver checking the >> timestamp in the MAC_Tx_Timestamp_Status_XXX registers, but I can only look >> into >> that feature later in the future. > > The problem you have is that the device tree binding is a Binary API > you have to keep backwards compatible with for the next 20 years. You > cannot drop this property when you do get around to finishing the > work. You also want to avoid adding more and more options, which > nobody knows what they do, and what best combination is to get the > best performance. You should be aiming for a driver which just works > without any configuration and with good performance. > >>> What sort of performance improvement did you get? Do you have some >>> benchmark numbers? >> >> My setup is FPGA based, so it will have lower performance values. >> Iperf results with >> "Drop Transmit Status" set: ~650Mbps. >> "Drop Transmit Status" unset: ~450Mbps. > > What percentage of your customers use FPGAs? When i look at the users > of this driver, i see ST, Allwinner, Rockchip, Meson, etc. So silicon, > not FPGA. Does it make sense to do performance measurements on FPGA, > when you say it has lower performance?
I don't understand your question. Synopsys is an IP vendor, so all recent IPs are available for prototyping as you can understand and so early development is done using a FPGA. I only mentioned that the values were from a FPGA based setup because you could think that they were low. Performance values are just an indication. > > Andrew > Joao
