net: mvneta: bm: add support for hardware buffer management

Buffer manager (BM) is a dedicated hardware unit that can be used by all
ethernet ports of Armada XP and 38x SoC's. It allows to offload CPU on RX
path by sparing DRAM access on refilling buffer pool, hardware-based
filling of descriptor ring data and better memory utilization due to HW
arbitration for using 'short' pools for small packets.

Tests performed with A388 SoC working as a network bridge between two
packet generators showed increase of maximum processed 64B packets by
~20k (~555k packets with BM enabled vs ~535 packets without BM). Also
when pushing 1500B-packets with a line rate achieved, CPU load decreased
from around 25% without BM to 20% with BM.

BM comprise up to 4 buffer pointers' (BP) rings kept in DRAM, which
are called external BP pools - BPPE. Allocating and releasing buffer
pointers (BP) to/from BPPE is performed indirectly by write/read access
to a dedicated internal SRAM, where internal BP pools (BPPI) are placed.
BM hardware controls status of BPPE automatically, as well as assigning
proper buffers to RX descriptors. For more details please refer to
Functional Specification of Armada XP or 38x SoC.

In order to enable support for a separate hardware block, common for all
ports, a new driver has to be implemented ('mvneta_bm'). It provides
initialization sequence of address space, clocks, registers, SRAM,
empty pools' structures and also obtaining optional configuration
from DT (please refer to device tree binding documentation). mvneta_bm
exposes also a necessary API to mvneta driver, as well as a dedicated
structure with BM information (bm_priv), whose presence is used as a
flag notifying of BM usage by port. It has to be ensured that mvneta_bm
probe is executed prior to the ones in ports' driver. In case BM is not
used or its probe fails, mvneta falls back to use software buffer
management.

A sequence executed in mvneta_probe function is modified in order to have
an access to needed resources before possible port's BM initialization is
done. According to port-pools mapping provided by DT appropriate registers
are configured and the buffer pools are filled. RX path is modified
accordingly. Becaues the hardware allows a wide variety of configuration
options, following assumptions are made:
* using BM mechanisms can be selectively disabled/enabled basing
  on DT configuration among the ports
* 'long' pool's single buffer size is tied to port's MTU
* using 'long' pool by port is obligatory and it cannot be shared
* using 'short' pool for smaller packets is optional
* one 'short' pool can be shared among all ports

This commit enables hardware buffer management operation cooperating with
existing mvneta driver. New device tree binding documentation is added and
the one of mvneta is updated accordingly.

[[email protected]: removed the suspend/resume part]

Signed-off-by: Marcin Wojtas <[email protected]>
Signed-off-by: Gregory CLEMENT <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: wojtas-marcin

Documentation/devicetree/bindings/net/marvell-armada-370-neta.txt

@@ -18,15 +18,30 @@ Optional properties:
   "core" for core clock and "bus" for the optional bus clock.
 
 
+Optional properties (valid only for Armada XP/38x):
+
+- buffer-manager: a phandle to a buffer manager node. Please refer to
+  Documentation/devicetree/bindings/net/marvell-neta-bm.txt
+- bm,pool-long: ID of a pool, that will accept all packets of a size
+  higher than 'short' pool's threshold (if set) and up to MTU value.
+  Obligatory, when the port is supposed to use hardware
+  buffer management.
+- bm,pool-short: ID of a pool, that will be used for accepting
+  packets of a size lower than given threshold. If not set, the port
+  will use a single 'long' pool for all packets, as defined above.
+
 Example:
 
-ethernet@d0070000 {
+ethernet@70000 {
 	compatible = "marvell,armada-370-neta";
-	reg = <0xd0070000 0x2500>;
+	reg = <0x70000 0x2500>;
 	interrupts = <8>;
 	clocks = <&gate_clk 4>;
 	tx-csum-limit = <9800>
 	status = "okay";
 	phy = <&phy0>;
 	phy-mode = "rgmii-id";
+	buffer-manager = <&bm>;
+	bm,pool-long = <0>;
+	bm,pool-short = <1>;
 };

Documentation/devicetree/bindings/net/marvell-neta-bm.txt

@@ -0,0 +1,49 @@
+* Marvell Armada 380/XP Buffer Manager driver (BM)
+
+Required properties:
+
+- compatible: should be "marvell,armada-380-neta-bm".
+- reg: address and length of the register set for the device.
+- clocks: a pointer to the reference clock for this device.
+- internal-mem: a phandle to BM internal SRAM definition.
+
+Optional properties (port):
+
+- pool<0 : 3>,capacity: size of external buffer pointers' ring maintained
+  in DRAM. Can be set for each pool (id 0 : 3) separately. The value has
+  to be chosen between 128 and 16352 and it also has to be aligned to 32.
+  Otherwise the driver would adjust a given number or choose default if
+  not set.
+- pool<0 : 3>,pkt-size: maximum size of a packet accepted by a given buffer
+  pointers' pool (id 0 : 3). It will be taken into consideration only when pool
+  type is 'short'. For 'long' ones it would be overridden by port's MTU.
+  If not set a driver will choose a default value.
+
+In order to see how to hook the BM to a given ethernet port, please
+refer to Documentation/devicetree/bindings/net/marvell-armada-370-neta.txt.
+
+Example:
+
+- main node:
+
+bm: bm@c8000 {
+	compatible = "marvell,armada-380-neta-bm";
+	reg = <0xc8000 0xac>;
+	clocks = <&gateclk 13>;
+	internal-mem = <&bm_bppi>;
+	status = "okay";
+	pool2,capacity = <4096>;
+	pool1,pkt-size = <512>;
+};
+
+- internal SRAM node:
+
+bm_bppi: bm-bppi {
+	compatible = "mmio-sram";
+	reg = <MBUS_ID(0x0c, 0x04) 0 0x100000>;
+	ranges = <0 MBUS_ID(0x0c, 0x04) 0 0x100000>;
+	#address-cells = <1>;
+	#size-cells = <1>;
+	clocks = <&gateclk 13>;
+	status = "okay";
+};

drivers/net/ethernet/marvell/Kconfig

@@ -40,6 +40,19 @@ config MVMDIO
 
 	  This driver is used by the MV643XX_ETH and MVNETA drivers.
 
+config MVNETA_BM
+	tristate "Marvell Armada 38x/XP network interface BM support"
+	depends on MVNETA
+	---help---
+	  This driver supports auxiliary block of the network
+	  interface units in the Marvell ARMADA XP and ARMADA 38x SoC
+	  family, which is called buffer manager.
+
+	  This driver, when enabled, strictly cooperates with mvneta
+	  driver and is common for all network ports of the devices,
+	  even for Armada 370 SoC, which doesn't support hardware
+	  buffer management.
+
 config MVNETA
 	tristate "Marvell Armada 370/38x/XP network interface support"
 	depends on PLAT_ORION

drivers/net/ethernet/marvell/Makefile

@@ -4,6 +4,7 @@
 
 obj-$(CONFIG_MVMDIO) += mvmdio.o
 obj-$(CONFIG_MV643XX_ETH) += mv643xx_eth.o
+obj-$(CONFIG_MVNETA_BM) += mvneta_bm.o
 obj-$(CONFIG_MVNETA) += mvneta.o
 obj-$(CONFIG_MVPP2) += mvpp2.o
 obj-$(CONFIG_PXA168_ETH) += pxa168_eth.o