diff options
Diffstat (limited to 'Documentation/networking')
| -rw-r--r-- | Documentation/networking/stmmac.txt | 143 | ||||
| -rw-r--r-- | Documentation/networking/timestamping.txt | 76 |
2 files changed, 189 insertions, 30 deletions
diff --git a/Documentation/networking/stmmac.txt b/Documentation/networking/stmmac.txt new file mode 100644 index 00000000000..7ee770b5ef5 --- /dev/null +++ b/Documentation/networking/stmmac.txt @@ -0,0 +1,143 @@ + STMicroelectronics 10/100/1000 Synopsys Ethernet driver + +Copyright (C) 2007-2010 STMicroelectronics Ltd +Author: Giuseppe Cavallaro <peppe.cavallaro@st.com> + +This is the driver for the MAC 10/100/1000 on-chip Ethernet controllers +(Synopsys IP blocks); it has been fully tested on STLinux platforms. + +Currently this network device driver is for all STM embedded MAC/GMAC +(7xxx SoCs). + +DWC Ether MAC 10/100/1000 Universal version 3.41a and DWC Ether MAC 10/100 +Universal version 4.0 have been used for developing the first code +implementation. + +Please, for more information also visit: www.stlinux.com + +1) Kernel Configuration +The kernel configuration option is STMMAC_ETH: + Device Drivers ---> Network device support ---> Ethernet (1000 Mbit) ---> + STMicroelectronics 10/100/1000 Ethernet driver (STMMAC_ETH) + +2) Driver parameters list: + debug: message level (0: no output, 16: all); + phyaddr: to manually provide the physical address to the PHY device; + dma_rxsize: DMA rx ring size; + 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: + stmmaceth=dma_rxsize:128,dma_txsize:512 + +4) Driver information and notes + +4.1) Transmit process +The xmit method is invoked when the kernel needs to transmit a packet; it sets +the descriptors in the ring and informs the DMA engine that there is a packet +ready to be transmitted. +Once the controller has finished transmitting the packet, an interrupt is +triggered; So the driver will be able to release the socket buffers. +By default, the driver sets the NETIF_F_SG bit in the features field of the +net_device structure enabling the scatter/gather feature. + +4.2) Receive process +When one or more packets are received, an interrupt happens. The interrupts +are not queued so the driver has to scan all the descriptors in the ring during +the receive process. +This is based on NAPI so the interrupt handler signals only if there is work to be +done, and it exits. +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. + +4.4) WOL +Wake up on Lan feature through Magic Frame is only supported for the GMAC +core. + +4.5) DMA descriptors +Driver handles both normal and enhanced descriptors. The latter has been only +tested on DWC Ether MAC 10/100/1000 Universal version 3.41a. + +4.6) Ethtool support +Ethtool is supported. Driver statistics and internal errors can be taken using: +ethtool -S ethX command. It is possible to dump registers etc. + +4.7) Jumbo and Segmentation Offloading +Jumbo frames are supported and tested for the GMAC. +The GSO has been also added but it's performed in software. +LRO is not supported. + +4.8) Physical +The driver is compatible with PAL to work with PHY and GPHY devices. + +4.9) Platform information +Several information came from the platform; please refer to the +driver's Header file in include/linux directory. + +struct plat_stmmacenet_data { + int bus_id; + int pbl; + int has_gmac; + void (*fix_mac_speed)(void *priv, unsigned int speed); + void (*bus_setup)(unsigned long ioaddr); +#ifdef CONFIG_STM_DRIVERS + struct stm_pad_config *pad_config; +#endif + void *bsp_priv; +}; + +Where: +- pbl (Programmable Burst Length) is maximum number of + beats to be transferred in one DMA transaction. + GMAC also enables the 4xPBL by default. +- fix_mac_speed and bus_setup are used to configure internal target + registers (on STM platforms); +- has_gmac: GMAC core is on board (get it at run-time in the next step); +- bus_id: bus identifier. + +struct plat_stmmacphy_data { + int bus_id; + int phy_addr; + unsigned int phy_mask; + int interface; + int (*phy_reset)(void *priv); + void *priv; +}; + +Where: +- bus_id: bus identifier; +- phy_addr: physical address used for the attached phy device; + set it to -1 to get it at run-time; +- interface: physical MII interface mode; +- phy_reset: hook to reset HW function. + +TODO: +- Continue to make the driver more generic and suitable for other Synopsys + Ethernet controllers used on other architectures (i.e. ARM). +- 10G controllers are not supported. +- MAC uses Normal descriptors and GMAC uses enhanced ones. + This is a limit that should be reviewed. MAC could want to + use the enhanced structure. +- Checksumming: Rx/Tx csum is done in HW in case of GMAC only. +- Review the timer optimisation code to use an embedded device that seems to be + available in new chip generations. diff --git a/Documentation/networking/timestamping.txt b/Documentation/networking/timestamping.txt index 0e58b453917..e8c8f4f06c6 100644 --- a/Documentation/networking/timestamping.txt +++ b/Documentation/networking/timestamping.txt @@ -41,11 +41,12 @@ SOF_TIMESTAMPING_SOFTWARE: return system time stamp generated in SOF_TIMESTAMPING_TX/RX determine how time stamps are generated. SOF_TIMESTAMPING_RAW/SYS determine how they are reported in the following control message: - struct scm_timestamping { - struct timespec systime; - struct timespec hwtimetrans; - struct timespec hwtimeraw; - }; + +struct scm_timestamping { + struct timespec systime; + struct timespec hwtimetrans; + struct timespec hwtimeraw; +}; recvmsg() can be used to get this control message for regular incoming packets. For send time stamps the outgoing packet is looped back to @@ -87,12 +88,13 @@ by the network device and will be empty without that support. SIOCSHWTSTAMP: Hardware time stamping must also be initialized for each device driver -that is expected to do hardware time stamping. The parameter is: +that is expected to do hardware time stamping. The parameter is defined in +/include/linux/net_tstamp.h as: struct hwtstamp_config { - int flags; /* no flags defined right now, must be zero */ - int tx_type; /* HWTSTAMP_TX_* */ - int rx_filter; /* HWTSTAMP_FILTER_* */ + int flags; /* no flags defined right now, must be zero */ + int tx_type; /* HWTSTAMP_TX_* */ + int rx_filter; /* HWTSTAMP_FILTER_* */ }; Desired behavior is passed into the kernel and to a specific device by @@ -139,42 +141,56 @@ enum { /* time stamp any incoming packet */ HWTSTAMP_FILTER_ALL, - /* return value: time stamp all packets requested plus some others */ - HWTSTAMP_FILTER_SOME, + /* return value: time stamp all packets requested plus some others */ + HWTSTAMP_FILTER_SOME, /* PTP v1, UDP, any kind of event packet */ HWTSTAMP_FILTER_PTP_V1_L4_EVENT, - ... + /* for the complete list of values, please check + * the include file /include/linux/net_tstamp.h + */ }; DEVICE IMPLEMENTATION A driver which supports hardware time stamping must support the -SIOCSHWTSTAMP ioctl. Time stamps for received packets must be stored -in the skb with skb_hwtstamp_set(). +SIOCSHWTSTAMP ioctl and update the supplied struct hwtstamp_config with +the actual values as described in the section on SIOCSHWTSTAMP. + +Time stamps for received packets must be stored in the skb. To get a pointer +to the shared time stamp structure of the skb call skb_hwtstamps(). Then +set the time stamps in the structure: + +struct skb_shared_hwtstamps { + /* hardware time stamp transformed into duration + * since arbitrary point in time + */ + ktime_t hwtstamp; + ktime_t syststamp; /* hwtstamp transformed to system time base */ +}; Time stamps for outgoing packets are to be generated as follows: -- In hard_start_xmit(), check if skb_hwtstamp_check_tx_hardware() - returns non-zero. If yes, then the driver is expected - to do hardware time stamping. +- In hard_start_xmit(), check if skb_tx(skb)->hardware is set no-zero. + If yes, then the driver is expected to do hardware time stamping. - If this is possible for the skb and requested, then declare - that the driver is doing the time stamping by calling - skb_hwtstamp_tx_in_progress(). A driver not supporting - hardware time stamping doesn't do that. A driver must never - touch sk_buff::tstamp! It is used to store how time stamping - for an outgoing packets is to be done. + that the driver is doing the time stamping by setting the field + skb_tx(skb)->in_progress non-zero. You might want to keep a pointer + to the associated skb for the next step and not free the skb. A driver + not supporting hardware time stamping doesn't do that. A driver must + never touch sk_buff::tstamp! It is used to store software generated + time stamps by the network subsystem. - As soon as the driver has sent the packet and/or obtained a hardware time stamp for it, it passes the time stamp back by calling skb_hwtstamp_tx() with the original skb, the raw - hardware time stamp and a handle to the device (necessary - to convert the hardware time stamp to system time). If obtaining - the hardware time stamp somehow fails, then the driver should - not fall back to software time stamping. The rationale is that - this would occur at a later time in the processing pipeline - than other software time stamping and therefore could lead - to unexpected deltas between time stamps. -- If the driver did not call skb_hwtstamp_tx_in_progress(), then + hardware time stamp. skb_hwtstamp_tx() clones the original skb and + adds the timestamps, therefore the original skb has to be freed now. + If obtaining the hardware time stamp somehow fails, then the driver + should not fall back to software time stamping. The rationale is that + this would occur at a later time in the processing pipeline than other + software time stamping and therefore could lead to unexpected deltas + between time stamps. +- If the driver did not call set skb_tx(skb)->in_progress, then dev_hard_start_xmit() checks whether software time stamping is wanted as fallback and potentially generates the time stamp. |