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diff --git a/Documentation/networking/device_drivers/wan/z8530book.rst b/Documentation/networking/device_drivers/wan/z8530book.rst deleted file mode 100644 index fea2c40e7973..000000000000 --- a/Documentation/networking/device_drivers/wan/z8530book.rst +++ /dev/null @@ -1,256 +0,0 @@ -======================= -Z8530 Programming Guide -======================= - -:Author: Alan Cox - -Introduction -============ - -The Z85x30 family synchronous/asynchronous controller chips are used on -a large number of cheap network interface cards. The kernel provides a -core interface layer that is designed to make it easy to provide WAN -services using this chip. - -The current driver only support synchronous operation. Merging the -asynchronous driver support into this code to allow any Z85x30 device to -be used as both a tty interface and as a synchronous controller is a -project for Linux post the 2.4 release - -Driver Modes -============ - -The Z85230 driver layer can drive Z8530, Z85C30 and Z85230 devices in -three different modes. Each mode can be applied to an individual channel -on the chip (each chip has two channels). - -The PIO synchronous mode supports the most common Z8530 wiring. Here the -chip is interface to the I/O and interrupt facilities of the host -machine but not to the DMA subsystem. When running PIO the Z8530 has -extremely tight timing requirements. Doing high speeds, even with a -Z85230 will be tricky. Typically you should expect to achieve at best -9600 baud with a Z8C530 and 64Kbits with a Z85230. - -The DMA mode supports the chip when it is configured to use dual DMA -channels on an ISA bus. The better cards tend to support this mode of -operation for a single channel. With DMA running the Z85230 tops out -when it starts to hit ISA DMA constraints at about 512Kbits. It is worth -noting here that many PC machines hang or crash when the chip is driven -fast enough to hold the ISA bus solid. - -Transmit DMA mode uses a single DMA channel. The DMA channel is used for -transmission as the transmit FIFO is smaller than the receive FIFO. it -gives better performance than pure PIO mode but is nowhere near as ideal -as pure DMA mode. - -Using the Z85230 driver -======================= - -The Z85230 driver provides the back end interface to your board. To -configure a Z8530 interface you need to detect the board and to identify -its ports and interrupt resources. It is also your problem to verify the -resources are available. - -Having identified the chip you need to fill in a struct z8530_dev, -which describes each chip. This object must exist until you finally -shutdown the board. Firstly zero the active field. This ensures nothing -goes off without you intending it. The irq field should be set to the -interrupt number of the chip. (Each chip has a single interrupt source -rather than each channel). You are responsible for allocating the -interrupt line. The interrupt handler should be set to -:c:func:`z8530_interrupt()`. The device id should be set to the -z8530_dev structure pointer. Whether the interrupt can be shared or not -is board dependent, and up to you to initialise. - -The structure holds two channel structures. Initialise chanA.ctrlio and -chanA.dataio with the address of the control and data ports. You can or -this with Z8530_PORT_SLEEP to indicate your interface needs the 5uS -delay for chip settling done in software. The PORT_SLEEP option is -architecture specific. Other flags may become available on future -platforms, eg for MMIO. Initialise the chanA.irqs to &z8530_nop to -start the chip up as disabled and discarding interrupt events. This -ensures that stray interrupts will be mopped up and not hang the bus. -Set chanA.dev to point to the device structure itself. The private and -name field you may use as you wish. The private field is unused by the -Z85230 layer. The name is used for error reporting and it may thus make -sense to make it match the network name. - -Repeat the same operation with the B channel if your chip has both -channels wired to something useful. This isn't always the case. If it is -not wired then the I/O values do not matter, but you must initialise -chanB.dev. - -If your board has DMA facilities then initialise the txdma and rxdma -fields for the relevant channels. You must also allocate the ISA DMA -channels and do any necessary board level initialisation to configure -them. The low level driver will do the Z8530 and DMA controller -programming but not board specific magic. - -Having initialised the device you can then call -:c:func:`z8530_init()`. This will probe the chip and reset it into -a known state. An identification sequence is then run to identify the -chip type. If the checks fail to pass the function returns a non zero -error code. Typically this indicates that the port given is not valid. -After this call the type field of the z8530_dev structure is -initialised to either Z8530, Z85C30 or Z85230 according to the chip -found. - -Once you have called z8530_init you can also make use of the utility -function :c:func:`z8530_describe()`. This provides a consistent -reporting format for the Z8530 devices, and allows all the drivers to -provide consistent reporting. - -Attaching Network Interfaces -============================ - -If you wish to use the network interface facilities of the driver, then -you need to attach a network device to each channel that is present and -in use. In addition to use the generic HDLC you need to follow some -additional plumbing rules. They may seem complex but a look at the -example hostess_sv11 driver should reassure you. - -The network device used for each channel should be pointed to by the -netdevice field of each channel. The hdlc-> priv field of the network -device points to your private data - you will need to be able to find -your private data from this. - -The way most drivers approach this particular problem is to create a -structure holding the Z8530 device definition and put that into the -private field of the network device. The network device fields of the -channels then point back to the network devices. - -If you wish to use the generic HDLC then you need to register the HDLC -device. - -Before you register your network device you will also need to provide -suitable handlers for most of the network device callbacks. See the -network device documentation for more details on this. - -Configuring And Activating The Port -=================================== - -The Z85230 driver provides helper functions and tables to load the port -registers on the Z8530 chips. When programming the register settings for -a channel be aware that the documentation recommends initialisation -orders. Strange things happen when these are not followed. - -:c:func:`z8530_channel_load()` takes an array of pairs of -initialisation values in an array of u8 type. The first value is the -Z8530 register number. Add 16 to indicate the alternate register bank on -the later chips. The array is terminated by a 255. - -The driver provides a pair of public tables. The z8530_hdlc_kilostream -table is for the UK 'Kilostream' service and also happens to cover most -other end host configurations. The z8530_hdlc_kilostream_85230 table -is the same configuration using the enhancements of the 85230 chip. The -configuration loaded is standard NRZ encoded synchronous data with HDLC -bitstuffing. All of the timing is taken from the other end of the link. - -When writing your own tables be aware that the driver internally tracks -register values. It may need to reload values. You should therefore be -sure to set registers 1-7, 9-11, 14 and 15 in all configurations. Where -the register settings depend on DMA selection the driver will update the -bits itself when you open or close. Loading a new table with the -interface open is not recommended. - -There are three standard configurations supported by the core code. In -PIO mode the interface is programmed up to use interrupt driven PIO. -This places high demands on the host processor to avoid latency. The -driver is written to take account of latency issues but it cannot avoid -latencies caused by other drivers, notably IDE in PIO mode. Because the -drivers allocate buffers you must also prevent MTU changes while the -port is open. - -Once the port is open it will call the rx_function of each channel -whenever a completed packet arrived. This is invoked from interrupt -context and passes you the channel and a network buffer (struct -sk_buff) holding the data. The data includes the CRC bytes so most -users will want to trim the last two bytes before processing the data. -This function is very timing critical. When you wish to simply discard -data the support code provides the function -:c:func:`z8530_null_rx()` to discard the data. - -To active PIO mode sending and receiving the ``z8530_sync_open`` is called. -This expects to be passed the network device and the channel. Typically -this is called from your network device open callback. On a failure a -non zero error status is returned. -The :c:func:`z8530_sync_close()` function shuts down a PIO -channel. This must be done before the channel is opened again and before -the driver shuts down and unloads. - -The ideal mode of operation is dual channel DMA mode. Here the kernel -driver will configure the board for DMA in both directions. The driver -also handles ISA DMA issues such as controller programming and the -memory range limit for you. This mode is activated by calling the -:c:func:`z8530_sync_dma_open()` function. On failure a non zero -error value is returned. Once this mode is activated it can be shut down -by calling the :c:func:`z8530_sync_dma_close()`. You must call -the close function matching the open mode you used. - -The final supported mode uses a single DMA channel to drive the transmit -side. As the Z85C30 has a larger FIFO on the receive channel this tends -to increase the maximum speed a little. This is activated by calling the -``z8530_sync_txdma_open``. This returns a non zero error code on failure. The -:c:func:`z8530_sync_txdma_close()` function closes down the Z8530 -interface from this mode. - -Network Layer Functions -======================= - -The Z8530 layer provides functions to queue packets for transmission. -The driver internally buffers the frame currently being transmitted and -one further frame (in order to keep back to back transmission running). -Any further buffering is up to the caller. - -The function :c:func:`z8530_queue_xmit()` takes a network buffer -in sk_buff format and queues it for transmission. The caller must -provide the entire packet with the exception of the bitstuffing and CRC. -This is normally done by the caller via the generic HDLC interface -layer. It returns 0 if the buffer has been queued and non zero values -for queue full. If the function accepts the buffer it becomes property -of the Z8530 layer and the caller should not free it. - -The function :c:func:`z8530_get_stats()` returns a pointer to an -internally maintained per interface statistics block. This provides most -of the interface code needed to implement the network layer get_stats -callback. - -Porting The Z8530 Driver -======================== - -The Z8530 driver is written to be portable. In DMA mode it makes -assumptions about the use of ISA DMA. These are probably warranted in -most cases as the Z85230 in particular was designed to glue to PC type -machines. The PIO mode makes no real assumptions. - -Should you need to retarget the Z8530 driver to another architecture the -only code that should need changing are the port I/O functions. At the -moment these assume PC I/O port accesses. This may not be appropriate -for all platforms. Replacing :c:func:`z8530_read_port()` and -``z8530_write_port`` is intended to be all that is required to port -this driver layer. - -Known Bugs And Assumptions -========================== - -Interrupt Locking - The locking in the driver is done via the global cli/sti lock. This - makes for relatively poor SMP performance. Switching this to use a - per device spin lock would probably materially improve performance. - -Occasional Failures - We have reports of occasional failures when run for very long - periods of time and the driver starts to receive junk frames. At the - moment the cause of this is not clear. - -Public Functions Provided -========================= - -.. kernel-doc:: drivers/net/wan/z85230.c - :export: - -Internal Functions -================== - -.. kernel-doc:: drivers/net/wan/z85230.c - :internal: |