diff options
Diffstat (limited to 'networking/dec_21140.rst')
| -rw-r--r-- | networking/dec_21140.rst | 236 |
1 files changed, 0 insertions, 236 deletions
diff --git a/networking/dec_21140.rst b/networking/dec_21140.rst deleted file mode 100644 index 5463b7d..0000000 --- a/networking/dec_21140.rst +++ /dev/null @@ -1,236 +0,0 @@ -.. SPDX-License-Identifier: CC-BY-SA-4.0 - -DEC 21140 Driver -################ - -DEC 21240 Driver Introduction -============================= - -.. COMMENT: XXX add back in cross reference to list of boards. - -One aim of our project is to port RTEMS on a standard PowerPC platform. To -achieve it, we have chosen a Motorola MCP750 board. This board includes an -Ethernet controller based on a DEC21140 chip. Because RTEMS has a TCP/IP stack, -we will have to develop the DEC21140 related ethernet driver for the PowerPC -port of RTEMS. As this controller is able to support 100Mbps network and as -there is a lot of PCI card using this DEC chip, we have decided to first -implement this driver on an Intel PC386 target to provide a solution for using -RTEMS on PC with the 100Mbps network and then to port this code on PowerPC in a -second phase. - -The aim of this document is to give some PCI board generalities and to explain -the software architecture of the RTEMS driver. Finally, we will see what will -be done for ChorusOs and Netboot environment . - -Document Revision History -========================= - -*Current release*: - -- Current applicable release is 1.0. - -*Existing releases*: - -- 1.0 : Released the 10/02/98. First version of this document. - -- 0.1 : First draft of this document - -*Planned releases*: - -- None planned today. - -DEC21140 PCI Board Generalities -=============================== - -.. COMMENT: XXX add crossreference to PCI Register Figure - -This chapter describes rapidely the PCI interface of this Ethernet controller. -The board we have chosen for our PC386 implementation is a D-Link DFE-500TX. -This is a dual-speed 10/100Mbps Ethernet PCI adapter with a DEC21140AF chip. -Like other PCI devices, this board has a PCI device's header containing some -required configuration registers, as shown in the PCI Register Figure. By -reading or writing these registers, a driver can obtain information about the -type of the board, the interrupt it uses, the mapping of the chip specific -registers, ... - -On Intel target, the chip specific registers can be accessed via 2 methods : -I/O port access or PCI address mapped access. We have chosen to implement the -PCI address access to obtain compatible source code to the port the driver on a -PowerPC target. - -.. COMMENT: PCI Device's Configuration Header Space Format - - -.. figure ../images/networking/PCIreg.png - :align: center - :alt: PCI Device's Configuration Header Space Format - -.. COMMENT: XXX add crossreference to PCI Register Figure - -On RTEMS, a PCI API exists. We have used it to configure the board. After -initializing this PCI module via the ``pci_initialize()`` function, we try to -detect the DEC21140 based ethernet board. This board is characterized by its -Vendor ID (0x1011) and its Device ID (0x0009). We give these arguments to -the``pcib_find_by_deviceid`` function which returns , if the device is present, -a pointer to the configuration header space (see PCI Registers Fgure). Once -this operation performed, the driver is able to extract the information it -needs to configure the board internal registers, like the interrupt line, the -base address,... The board internal registers will not be detailled here. You -can find them in *DIGITAL Semiconductor 21140A PCI Fast Ethernet LAN Controller -- Hardware Reference Manual*. - -.. COMMENT: fix citation - -RTEMS Driver Software Architecture -================================== - -In this chapter will see the initialization phase, how the controller uses the -host memory and the 2 threads launched at the initialization time. - -Initialization phase --------------------- - -The DEC21140 Ethernet driver keeps the same software architecture than the -other RTEMS ethernet drivers. The only API the programmer can use is the -``rtems_dec21140_driver_attach(struct rtems_bsdnet_ifconfig *config)`` -function which detects the board and initializes the associated data structure -(with registers base address, entry points to low-level initialization -function,...), if the board is found. - -Once the attach function executed, the driver initializes the DEC chip. Then -the driver connects an interrupt handler to the interrupt line driven by the -Ethernet controller (the only interrupt which will be treated is the receive -interrupt) and launches 2 threads : a receiver thread and a transmitter -thread. Then the driver waits for incoming frame to give to the protocol stack -or outcoming frame to send on the physical link. - -Memory Buffer -------------- - -.. COMMENT: XXX add cross reference to Problem - -This DEC chip uses the host memory to store the incoming Ethernet frames and -the descriptor of these frames. We have chosen to use 7 receive buffers and 1 -transmit buffer to optimize memory allocation due to cache and paging problem -that will be explained in the section *Encountered Problems*. - -To reference these buffers to the DEC chip we use a buffer descriptors -ring. The descriptor structure is defined in the Buffer Descriptor Figure. -Each descriptor can reference one or two memory buffers. We choose to use only -one buffer of 1520 bytes per descriptor. - -The difference between a receive and a transmit buffer descriptor is located in -the status and control bits fields. We do not give details here, please refer -to the DEC21140 Hardware Manual. - -.. COMMENT: Buffer Descriptor - - -.. figure:: ../images/networking/recvbd.png - :align: center - :alt: Buffer Descriptor - -Receiver Thread ---------------- - -This thread is event driven. Each time a DEC PCI board interrupt occurs, the -handler checks if this is a receive interrupt and send an event "reception" to -the receiver thread which looks into the entire buffer descriptors ring the -ones that contain a valid incoming frame (bit OWN=0 means descriptor belongs to -host processor). Each valid incoming ethernet frame is sent to the protocol -stack and the buffer descriptor is given back to the DEC board (the host -processor reset bit OWN, which means descriptor belongs to 21140). - -Transmitter Thread ------------------- - -This thread is also event driven. Each time an Ethernet frame is put in the -transmit queue, an event is sent to the transmit thread, which empty the queue -by sending each outcoming frame. Because we use only one transmit buffer, we -are sure that the frame is well-sent before sending the next. - -Encountered Problems -==================== - -On Intel PC386 target, we were faced with a problem of memory cache management. -Because the DEC chip uses the host memory to store the incoming frame and -because the DEC21140 configuration registers are mapped into the PCI address -space, we must ensure that the data read (or written) by the host processor are -the ones written (or read) by the DEC21140 device in the host memory and not -old data stored in the cache memory. Therefore, we had to provide a way to -manage the cache. This module is described in the document *RTEMS Cache -Management For Intel*. On Intel, the memory region cache management is -available only if the paging unit is enabled. We have used this paging -mechanism, with 4Kb page. All the buffers allocated to store the incoming or -outcoming frames, buffer descriptor and also the PCI address space of the DEC -board are located in a memory space with cache disable. - -Concerning the buffers and their descriptors, we have tried to optimize the -memory space in term of allocated page. One buffer has 1520 bytes, one -descriptor has 16 bytes. We have 7 receive buffers and 1 transmit buffer, and -for each, 1 descriptor : (7+1)*(1520+16) = 12288 bytes = 12Kb = 3 entire -pages. This allows not to lose too much memory or not to disable cache memory -for a page which contains other data than buffer, which could decrease -performance. - -Netboot DEC driver -================== - -We use Netboot tool to load our development from a server to the target via an -ethernet network. Currently, this tool does not support the DEC board. We plan -to port the DEC driver for the Netboot tool. - -But concerning the port of the DEC driver into Netboot, we are faced with a -problem: in RTEMS environment, the DEC driver is interrupt or event driven, in -Netboot environment, it must be used in polling mode. It means that we will -have to re-write some mechanisms of this driver. - -List of Ethernet cards using the DEC chip -========================================= - -Many Ethernet adapter cards use the Tulip chip. Here is a non exhaustive list -of adapters which support this driver : - -- Accton EtherDuo PCI. - -- Accton EN1207 All three media types supported. - -- Adaptec ANA6911/TX 21140-AC. - -- Cogent EM110 21140-A with DP83840 N-Way MII transceiver. - -- Cogent EM400 EM100 with 4 21140 100mbps-only ports + PCI Bridge. - -- Danpex EN-9400P3. - -- D-Link DFE500-Tx 21140-A with DP83840 transceiver. - -- Kingston EtherX KNE100TX 21140AE. - -- Netgear FX310 TX 10/100 21140AE. - -- SMC EtherPower10/100 With DEC21140 and 68836 SYM transceiver. - -- SMC EtherPower10/100 With DEC21140-AC and DP83840 MII transceiver. - Note: The EtherPower II uses the EPIC chip, which requires a different driver. - -- Surecom EP-320X DEC 21140. - -- Thomas Conrad TC5048. - -- Znyx ZX345 21140-A, usually with the DP83840 N-Way MII transciever. Some ZX345 - cards made in 1996 have an ICS 1890 transciver instead. - -- ZNYX ZX348 Two 21140-A chips using ICS 1890 transcievers and either a 21052 - or 21152 bridge. Early versions used National 83840 transcievers, but later - versions are depopulated ZX346 boards. - -- ZNYX ZX351 21140 chip with a Broadcom 100BaseT4 transciever. - -Our DEC driver has not been tested with all these cards, only with the D-Link -DFE500-TX. - -- DEC21140 Hardware Manual DIGITAL, DIGITAL Semiconductor 21140A PCI Fast - Ethernet LAN Controller - Hardware Reference Manual**. - -- *[99.TA.0021.M.ER]Emmanuel Raguet,*RTEMS Cache Management For Intel**. |