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DM9000: Add documentation for the driver.
Add Documentation/networking/dm9000.txt for the DM9000 network driver. Signed-off-by: Ben Dooks <ben-linux@fluff.org> Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
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Ben Dooks
Jeff Garzik
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Documentation/networking/dm9000.txt
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Documentation/networking/dm9000.txt
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DM9000 Network driver
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=====================
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Copyright 2008 Simtec Electronics,
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Ben Dooks <ben@simtec.co.uk> <ben-linux@fluff.org>
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Introduction
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------------
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This file describes how to use the DM9000 platform-device based network driver
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that is contained in the files drivers/net/dm9000.c and drivers/net/dm9000.h.
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The driver supports three DM9000 variants, the DM9000E which is the first chip
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supported as well as the newer DM9000A and DM9000B devices. It is currently
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maintained and tested by Ben Dooks, who should be CC: to any patches for this
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driver.
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Defining the platform device
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----------------------------
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The minimum set of resources attached to the platform device are as follows:
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1) The physical address of the address register
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2) The physical address of the data register
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3) The IRQ line the device's interrupt pin is connected to.
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These resources should be specified in that order, as the ordering of the
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two address regions is important (the driver expects these to be address
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and then data).
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An example from arch/arm/mach-s3c2410/mach-bast.c is:
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static struct resource bast_dm9k_resource[] = {
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[0] = {
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.start = S3C2410_CS5 + BAST_PA_DM9000,
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.end = S3C2410_CS5 + BAST_PA_DM9000 + 3,
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.flags = IORESOURCE_MEM,
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},
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[1] = {
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.start = S3C2410_CS5 + BAST_PA_DM9000 + 0x40,
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.end = S3C2410_CS5 + BAST_PA_DM9000 + 0x40 + 0x3f,
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.flags = IORESOURCE_MEM,
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},
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[2] = {
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.start = IRQ_DM9000,
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.end = IRQ_DM9000,
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.flags = IORESOURCE_IRQ | IORESOURCE_IRQ_HIGHLEVEL,
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}
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};
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static struct platform_device bast_device_dm9k = {
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.name = "dm9000",
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.id = 0,
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.num_resources = ARRAY_SIZE(bast_dm9k_resource),
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.resource = bast_dm9k_resource,
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};
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Note the setting of the IRQ trigger flag in bast_dm9k_resource[2].flags,
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as this will generate a warning if it is not present. The trigger from
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the flags field will be passed to request_irq() when registering the IRQ
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handler to ensure that the IRQ is setup correctly.
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This shows a typical platform device, without the optional configuration
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platform data supplied. The next example uses the same resources, but adds
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the optional platform data to pass extra configuration data:
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static struct dm9000_plat_data bast_dm9k_platdata = {
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.flags = DM9000_PLATF_16BITONLY,
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};
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static struct platform_device bast_device_dm9k = {
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.name = "dm9000",
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.id = 0,
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.num_resources = ARRAY_SIZE(bast_dm9k_resource),
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.resource = bast_dm9k_resource,
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.dev = {
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.platform_data = &bast_dm9k_platdata,
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}
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};
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The platform data is defined in include/linux/dm9000.h and described below.
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Platform data
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-------------
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Extra platform data for the DM9000 can describe the IO bus width to the
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device, whether or not an external PHY is attached to the device and
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the availability of an external configuration EEPROM.
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The flags for the platform data .flags field are as follows:
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DM9000_PLATF_8BITONLY
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The IO should be done with 8bit operations.
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DM9000_PLATF_16BITONLY
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The IO should be done with 16bit operations.
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DM9000_PLATF_32BITONLY
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The IO should be done with 32bit operations.
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DM9000_PLATF_EXT_PHY
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The chip is connected to an external PHY.
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DM9000_PLATF_NO_EEPROM
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This can be used to signify that the board does not have an
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EEPROM, or that the EEPROM should be hidden from the user.
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DM9000_PLATF_SIMPLE_PHY
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Switch to using the simpler PHY polling method which does not
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try and read the MII PHY state regularly. This is only available
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when using the internal PHY. See the section on link state polling
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for more information.
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The config symbol DM9000_FORCE_SIMPLE_PHY_POLL, Kconfig entry
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"Force simple NSR based PHY polling" allows this flag to be
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forced on at build time.
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PHY Link state polling
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----------------------
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The driver keeps track of the link state and informs the network core
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about link (carrier) availablilty. This is managed by several methods
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depending on the version of the chip and on which PHY is being used.
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For the internal PHY, the original (and currently default) method is
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to read the MII state, either when the status changes if we have the
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necessary interrupt support in the chip or every two seconds via a
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periodic timer.
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To reduce the overhead for the internal PHY, there is now the option
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of using the DM9000_FORCE_SIMPLE_PHY_POLL config, or DM9000_PLATF_SIMPLE_PHY
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platform data option to read the summary information without the
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expensive MII accesses. This method is faster, but does not print
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as much information.
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When using an external PHY, the driver currently has to poll the MII
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link status as there is no method for getting an interrupt on link change.
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DM9000A / DM9000B
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-----------------
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These chips are functionally similar to the DM9000E and are supported easily
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by the same driver. The features are:
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1) Interrupt on internal PHY state change. This means that the periodic
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polling of the PHY status may be disabled on these devices when using
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the internal PHY.
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2) TCP/UDP checksum offloading, which the driver does not currently support.
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ethtool
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-------
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The driver supports the ethtool interface for access to the driver
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state information, the PHY state and the EEPROM.
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