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-<?xml version="1.0" encoding="UTF-8"?>
-<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
- "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
-
-<book id="Z85230Guide">
- <bookinfo>
- <title>Z8530 Programming Guide</title>
-
- <authorgroup>
- <author>
- <firstname>Alan</firstname>
- <surname>Cox</surname>
- <affiliation>
- <address>
- <email>alan@lxorguk.ukuu.org.uk</email>
- </address>
- </affiliation>
- </author>
- </authorgroup>
-
- <copyright>
- <year>2000</year>
- <holder>Alan Cox</holder>
- </copyright>
-
- <legalnotice>
- <para>
- This documentation is free software; you can redistribute
- it and/or modify it under the terms of the GNU General Public
- License as published by the Free Software Foundation; either
- version 2 of the License, or (at your option) any later
- version.
- </para>
-
- <para>
- This program is distributed in the hope that it will be
- useful, but WITHOUT ANY WARRANTY; without even the implied
- warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
- See the GNU General Public License for more details.
- </para>
-
- <para>
- You should have received a copy of the GNU General Public
- License along with this program; if not, write to the Free
- Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
- MA 02111-1307 USA
- </para>
-
- <para>
- For more details see the file COPYING in the source
- distribution of Linux.
- </para>
- </legalnotice>
- </bookinfo>
-
-<toc></toc>
-
- <chapter id="intro">
- <title>Introduction</title>
- <para>
- 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.
- </para>
- <para>
- 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
- </para>
- </chapter>
-
- <chapter id="Driver_Modes">
- <title>Driver Modes</title>
- <para>
- 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).
- </para>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- </chapter>
-
- <chapter id="Using_the_Z85230_driver">
- <title>Using the Z85230 driver</title>
- <para>
- 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.
- </para>
- <para>
- 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 <function>z8530_interrupt</function>. 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.
- </para>
- <para>
- 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 &amp;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.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- Having initialised the device you can then call
- <function>z8530_init</function>. 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.
- </para>
- <para>
- Once you have called z8530_init you can also make use of the utility
- function <function>z8530_describe</function>. This provides a
- consistent reporting format for the Z8530 devices, and allows all
- the drivers to provide consistent reporting.
- </para>
- </chapter>
-
- <chapter id="Attaching_Network_Interfaces">
- <title>Attaching Network Interfaces</title>
- <para>
- 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.
- </para>
- <para>
- The network device used for each channel should be pointed to by
- the netdevice field of each channel. The hdlc-&gt; priv field of the
- network device points to your private data - you will need to be
- able to find your private data from this.
- </para>
- <para>
- 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.
- </para>
- <para>
- If you wish to use the generic HDLC then you need to register
- the HDLC device.
- </para>
- <para>
- 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.
- </para>
- </chapter>
-
- <chapter id="Configuring_And_Activating_The_Port">
- <title>Configuring And Activating The Port</title>
- <para>
- 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.
- </para>
- <para>
- <function>z8530_channel_load</function> 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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 <function>z8530_null_rx</function>
- to discard the data.
- </para>
- <para>
- To active PIO mode sending and receiving the <function>
- z8530_sync_open</function> 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 <function>z8530_sync_close</function>
- function shuts down a PIO channel. This must be done before the
- channel is opened again and before the driver shuts down
- and unloads.
- </para>
- <para>
- 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 <function>z8530_sync_dma_open</function>
- function. On failure a non zero error value is returned.
- Once this mode is activated it can be shut down by calling the
- <function>z8530_sync_dma_close</function>. You must call the close
- function matching the open mode you used.
- </para>
- <para>
- 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 <function>z8530_sync_txdma_open
- </function>. This returns a non zero error code on failure. The
- <function>z8530_sync_txdma_close</function> function closes down
- the Z8530 interface from this mode.
- </para>
- </chapter>
-
- <chapter id="Network_Layer_Functions">
- <title>Network Layer Functions</title>
- <para>
- 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.
- </para>
- <para>
- The function <function>z8530_queue_xmit</function> 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.
- </para>
- <para>
- The function <function>z8530_get_stats</function> 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.
- </para>
- </chapter>
-
- <chapter id="Porting_The_Z8530_Driver">
- <title>Porting The Z8530 Driver</title>
- <para>
- 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.
- </para>
- <para>
- 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
- <function>z8530_read_port</function> and <function>z8530_write_port
- </function> is intended to be all that is required to port this
- driver layer.
- </para>
- </chapter>
-
- <chapter id="bugs">
- <title>Known Bugs And Assumptions</title>
- <para>
- <variablelist>
- <varlistentry><term>Interrupt Locking</term>
- <listitem>
- <para>
- 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.
- </para>
- </listitem></varlistentry>
-
- <varlistentry><term>Occasional Failures</term>
- <listitem>
- <para>
- 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.
- </para>
- </listitem></varlistentry>
- </variablelist>
-
- </para>
- </chapter>
-
- <chapter id="pubfunctions">
- <title>Public Functions Provided</title>
-!Edrivers/net/wan/z85230.c
- </chapter>
-
- <chapter id="intfunctions">
- <title>Internal Functions</title>
-!Idrivers/net/wan/z85230.c
- </chapter>
-
-</book>