From: Stefan Chulski <stef...@marvell.com> Armada hardware has a pause generation mechanism in GOP (MAC). The GOP generate flow control frames based on an indication programmed in Ports Control 0 Register. There is a bit per port. However assertion of the PortX Pause bits in the ports control 0 register only sends a one time pause. To complement the function the GOP has a mechanism to periodically send pause control messages based on periodic counters. This mechanism ensures that the pause is effective as long as the Appropriate PortX Pause is asserted.
Problem is that Packet Processor that actually can drop packets due to lack of resources not connected to the GOP flow control generation mechanism. To solve this issue Armada has firmware running on CM3 CPU dedicated for Flow Control support. Firmware monitors Packet Processor resources and asserts XON/XOFF by writing to Ports Control 0 Register. MSS shared SRAM memory used to communicate between CM3 firmware and PP2 driver. During init PP2 driver informs firmware about used BM pools, RXQs, congestion and depletion thresholds. The pause frames are generated whenever congestion or depletion in resources is detected. The back pressure is stopped when the resource reaches a sufficient level. So the congestion/depletion and sufficient level implement a hysteresis that reduces the XON/XOFF toggle frequency. Packet Processor v23 hardware introduces support for RX FIFO fill level monitor. Patch "add PPv23 version definition" to differ between v23 and v22 hardware. Patch "add TX FC firmware check" verifies that CM3 firmware supports Flow Control monitoring. v1 --> v2 - Add memory requirements information - Add EPROBE_DEFER if of_gen_pool_get return NULL - Move Flow control configuration to mvpp2_mac_link_up callback - Add firmware version info with Flow control support Konstantin Porotchkin (1): dts: marvell: add CM3 SRAM memory to cp115 ethernet device tree Stefan Chulski (17): doc: marvell: add cm3-mem device tree bindings description net: mvpp2: add CM3 SRAM memory map net: mvpp2: add PPv23 version definition net: mvpp2: always compare hw-version vs MVPP21 net: mvpp2: increase BM pool size to 2048 buffers net: mvpp2: increase RXQ size to 1024 descriptors net: mvpp2: add FCA periodic timer configurations net: mvpp2: add FCA RXQ non occupied descriptor threshold net: mvpp2: add spinlock for FW FCA configuration path net: mvpp2: enable global flow control net: mvpp2: add RXQ flow control configurations net: mvpp2: add ethtool flow control configuration support net: mvpp2: add BM protection underrun feature support net: mvpp2: add PPv23 RX FIFO flow control net: mvpp2: set 802.3x GoP Flow Control mode net: mvpp2: limit minimum ring size to 1024 descriptors net: mvpp2: add TX FC firmware check Documentation/devicetree/bindings/net/marvell-pp2.txt | 1 + arch/arm64/boot/dts/marvell/armada-cp11x.dtsi | 10 + drivers/net/ethernet/marvell/mvpp2/mvpp2.h | 130 ++++- drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c | 558 +++++++++++++++++++- 4 files changed, 657 insertions(+), 42 deletions(-) -- 1.9.1
