>-----Original Message----- >From: Vladimir Oltean <olteanv@xxxxxxxxx> >Sent: Saturday, April 17, 2021 2:42 AM >To: Jakub Kicinski <kuba@xxxxxxxxxx>; David S. Miller ><davem@xxxxxxxxxxxxx>; netdev@xxxxxxxxxxxxxxx; Po Liu ><po.liu@xxxxxxx> >Cc: Claudiu Manoil <claudiu.manoil@xxxxxxx>; Alexandru Marginean ><alexandru.marginean@xxxxxxx>; Rob Herring <robh+dt@xxxxxxxxxx>; >Shawn Guo <shawnguo@xxxxxxxxxx>; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; >devicetree@xxxxxxxxxxxxxxx; Russell King - ARM Linux admin ><linux@xxxxxxxxxxxxxxx>; Andrew Lunn <andrew@xxxxxxx>; Michael Walle ><michael@xxxxxxxx>; Vladimir Oltean <vladimir.oltean@xxxxxxx> >Subject: [PATCH net-next 5/5] net: enetc: add support for flow control > >From: Vladimir Oltean <vladimir.oltean@xxxxxxx> > >In the ENETC receive path, a frame received by the MAC is first stored >in a 256KB 'FIFO' memory, then transferred to DRAM when enqueuing it to >the RX ring. The FIFO is a shared resource for all ENETC ports, but >every port keeps track of its own memory utilization, on RX and on TX. > >There is a setting for RX rings through which they can either operate in >'lossy' mode (where the lack of a free buffer causes an immediate >discard of the frame) or in 'lossless' mode (where the lack of a free >buffer in the ring makes the frame stay longer in the FIFO). > >In turn, when the memory utilization of the FIFO exceeds a certain >margin, the MAC can be configured to emit PAUSE frames. > >There is enough FIFO memory to buffer up to 3 MTU-sized frames per RX >port while not jeopardizing the other use cases (jumbo frames), and >also not consume bytes from the port TX allocations. Also, 3 MTU-sized >frames worth of memory is enough to ensure zero loss for 64 byte packets >at 1G line rate. > >Signed-off-by: Vladimir Oltean <vladimir.oltean@xxxxxxx> Reviewed-by: Claudiu Manoil <claudiu.manoil@xxxxxxx>
