path: root/Documentation/networking/stmmac.txt
diff options
Diffstat (limited to 'Documentation/networking/stmmac.txt')
1 files changed, 45 insertions, 24 deletions
diff --git a/Documentation/networking/stmmac.txt b/Documentation/networking/stmmac.txt
index 5cb9a197246..f9fa6db40a5 100644
--- a/Documentation/networking/stmmac.txt
+++ b/Documentation/networking/stmmac.txt
@@ -29,11 +29,9 @@ The kernel configuration option is STMMAC_ETH:
dma_txsize: DMA tx ring size;
buf_sz: DMA buffer size;
tc: control the HW FIFO threshold;
- tx_coe: Enable/Disable Tx Checksum Offload engine;
watchdog: transmit timeout (in milliseconds);
flow_ctrl: Flow control ability [on/off];
pause: Flow Control Pause Time;
- tmrate: timer period (only if timer optimisation is configured).
3) Command line options
Driver parameters can be also passed in command line by using:
@@ -60,17 +58,19 @@ Then the poll method will be scheduled at some future point.
The incoming packets are stored, by the DMA, in a list of pre-allocated socket
buffers in order to avoid the memcpy (Zero-copy).
-4.3) Timer-Driver Interrupt
-Instead of having the device that asynchronously notifies the frame receptions,
-the driver configures a timer to generate an interrupt at regular intervals.
-Based on the granularity of the timer, the frames that are received by the
-device will experience different levels of latency. Some NICs have dedicated
-timer device to perform this task. STMMAC can use either the RTC device or the
-TMU channel 2 on STLinux platforms.
-The timers frequency can be passed to the driver as parameter; when change it,
-take care of both hardware capability and network stability/performance impact.
-Several performance tests on STM platforms showed this optimisation allows to
-spare the CPU while having the maximum throughput.
+4.3) Interrupt Mitigation
+The driver is able to mitigate the number of its DMA interrupts
+using NAPI for the reception on chips older than the 3.50.
+New chips have an HW RX-Watchdog used for this mitigation.
+On Tx-side, the mitigation schema is based on a SW timer that calls the
+tx function (stmmac_tx) to reclaim the resource after transmitting the
+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).
+Mitigation parameters can be tuned by ethtool.
4.4) WOL
Wake up on Lan feature through Magic and Unicast frames are supported for the
@@ -121,6 +121,7 @@ struct plat_stmmacenet_data {
int bugged_jumbo;
int pmt;
int force_sf_dma_mode;
+ int riwt_off;
void (*fix_mac_speed)(void *priv, unsigned int speed);
void (*bus_setup)(void __iomem *ioaddr);
int (*init)(struct platform_device *pdev);
@@ -156,6 +157,7 @@ Where:
o pmt: core has the embedded power module (optional).
o force_sf_dma_mode: force DMA to use the Store and Forward mode
instead of the Threshold.
+ o riwt_off: force to disable the RX watchdog feature and switch to NAPI mode.
o fix_mac_speed: this callback is used for modifying some syscfg registers
(on ST SoCs) according to the link speed negotiated by the
physical layer .
@@ -173,7 +175,6 @@ Where:
For MDIO bus The we have:
struct stmmac_mdio_bus_data {
- int bus_id;
int (*phy_reset)(void *priv);
unsigned int phy_mask;
int *irqs;
@@ -181,7 +182,6 @@ For MDIO bus The we have:
- o bus_id: bus identifier;
o phy_reset: hook to reset the phy device attached to the bus.
o phy_mask: phy mask passed when register the MDIO bus within the driver.
o irqs: list of IRQs, one per PHY.
@@ -230,9 +230,6 @@ there are two MAC cores: one MAC is for MDIO Bus/PHY emulation
with fixed_link support.
static struct stmmac_mdio_bus_data stmmac1_mdio_bus = {
- .bus_id = 1,
- |
- |-> phy device on the bus_id 1
.phy_reset = phy_reset;
|-> function to provide the phy_reset on this board
@@ -257,9 +254,11 @@ reset procedure etc).
o Makefile
o stmmac_main.c: main network device driver;
o stmmac_mdio.c: mdio functions;
+ o stmmac_pci: PCI driver;
+ o stmmac_platform.c: platform driver
o stmmac_ethtool.c: ethtool support;
o stmmac_timer.[ch]: timer code used for mitigating the driver dma interrupts
- Only tested on ST40 platforms based.
+ (only tested on ST40 platforms based);
o stmmac.h: private driver structure;
o common.h: common definitions and VFTs;
o descs.h: descriptor structure definitions;
@@ -269,9 +268,11 @@ reset procedure etc).
o dwmac100_core: MAC 100 core and dma code;
o dwmac100_dma.c: dma funtions for the MAC chip;
o dwmac1000.h: specific header file for the MAC;
- o dwmac_lib.c: generic DMA functions shared among chips
- o enh_desc.c: functions for handling enhanced descriptors
- o norm_desc.c: functions for handling normal descriptors
+ o dwmac_lib.c: generic DMA functions shared among chips;
+ o enh_desc.c: functions for handling enhanced descriptors;
+ o norm_desc.c: functions for handling normal descriptors;
+ o chain_mode.c/ring_mode.c:: functions to manage RING/CHAINED modes;
+ o mmc_core.c/mmc.h: Management MAC Counters;
5) Debug Information
@@ -304,7 +305,27 @@ All these are only useful during the developing stage
and should never enabled inside the code for general usage.
In fact, these can generate an huge amount of debug messages.
-6) TODO:
+6) Energy Efficient Ethernet
+Energy Efficient Ethernet(EEE) enables IEEE 802.3 MAC sublayer along
+with a family of Physical layer to operate in the Low power Idle(LPI)
+mode. The EEE mode supports the IEEE 802.3 MAC operation at 100Mbps,
+1000Mbps & 10Gbps.
+The LPI mode allows power saving by switching off parts of the
+communication device functionality when there is no data to be
+transmitted & received. The system on both the side of the link can
+disable some functionalities & save power during the period of low-link
+utilization. The MAC controls whether the system should enter or exit
+the LPI mode & communicate this to PHY.
+As soon as the interface is opened, the driver verifies if the EEE can
+be supported. This is done by looking at both the DMA HW capability
+register and the PHY devices MCD registers.
+To enter in Tx LPI mode the driver needs to have a software timer
+that enable and disable the LPI mode when there is nothing to be
+7) TODO:
o XGMAC is not supported.
- o Add the EEE - Energy Efficient Ethernet
o Add the PTP - precision time protocol