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authorJeff Garzik <jgarzik@pobox.com>2005-09-01 18:02:01 -0400
committerJeff Garzik <jgarzik@pobox.com>2005-09-01 18:02:01 -0400
commite3ee3b78f83688a0ae4315e8be71b2eac559904a (patch)
treedeb03bcdd020262af450ed23382d7c921263f5cf /Documentation/networking
parent91cb70c1769d9b72dd1efe40c31f01005820b09e (diff)
parent6b39374a27eb4be7e9d82145ae270ba02ea90dc8 (diff)
downloadlinux-next-e3ee3b78f83688a0ae4315e8be71b2eac559904a.tar.gz
/spare/repo/netdev-2.6 branch 'master'
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-rw-r--r--Documentation/networking/phy.txt288
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diff --git a/Documentation/networking/cxgb.txt b/Documentation/networking/cxgb.txt
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+ Chelsio N210 10Gb Ethernet Network Controller
+
+ Driver Release Notes for Linux
+
+ Version 2.1.1
+
+ June 20, 2005
+
+CONTENTS
+========
+ INTRODUCTION
+ FEATURES
+ PERFORMANCE
+ DRIVER MESSAGES
+ KNOWN ISSUES
+ SUPPORT
+
+
+INTRODUCTION
+============
+
+ This document describes the Linux driver for Chelsio 10Gb Ethernet Network
+ Controller. This driver supports the Chelsio N210 NIC and is backward
+ compatible with the Chelsio N110 model 10Gb NICs.
+
+
+FEATURES
+========
+
+ Adaptive Interrupts (adaptive-rx)
+ ---------------------------------
+
+ This feature provides an adaptive algorithm that adjusts the interrupt
+ coalescing parameters, allowing the driver to dynamically adapt the latency
+ settings to achieve the highest performance during various types of network
+ load.
+
+ The interface used to control this feature is ethtool. Please see the
+ ethtool manpage for additional usage information.
+
+ By default, adaptive-rx is disabled.
+ To enable adaptive-rx:
+
+ ethtool -C <interface> adaptive-rx on
+
+ To disable adaptive-rx, use ethtool:
+
+ ethtool -C <interface> adaptive-rx off
+
+ After disabling adaptive-rx, the timer latency value will be set to 50us.
+ You may set the timer latency after disabling adaptive-rx:
+
+ ethtool -C <interface> rx-usecs <microseconds>
+
+ An example to set the timer latency value to 100us on eth0:
+
+ ethtool -C eth0 rx-usecs 100
+
+ You may also provide a timer latency value while disabling adpative-rx:
+
+ ethtool -C <interface> adaptive-rx off rx-usecs <microseconds>
+
+ If adaptive-rx is disabled and a timer latency value is specified, the timer
+ will be set to the specified value until changed by the user or until
+ adaptive-rx is enabled.
+
+ To view the status of the adaptive-rx and timer latency values:
+
+ ethtool -c <interface>
+
+
+ TCP Segmentation Offloading (TSO) Support
+ -----------------------------------------
+
+ This feature, also known as "large send", enables a system's protocol stack
+ to offload portions of outbound TCP processing to a network interface card
+ thereby reducing system CPU utilization and enhancing performance.
+
+ The interface used to control this feature is ethtool version 1.8 or higher.
+ Please see the ethtool manpage for additional usage information.
+
+ By default, TSO is enabled.
+ To disable TSO:
+
+ ethtool -K <interface> tso off
+
+ To enable TSO:
+
+ ethtool -K <interface> tso on
+
+ To view the status of TSO:
+
+ ethtool -k <interface>
+
+
+PERFORMANCE
+===========
+
+ The following information is provided as an example of how to change system
+ parameters for "performance tuning" an what value to use. You may or may not
+ want to change these system parameters, depending on your server/workstation
+ application. Doing so is not warranted in any way by Chelsio Communications,
+ and is done at "YOUR OWN RISK". Chelsio will not be held responsible for loss
+ of data or damage to equipment.
+
+ Your distribution may have a different way of doing things, or you may prefer
+ a different method. These commands are shown only to provide an example of
+ what to do and are by no means definitive.
+
+ Making any of the following system changes will only last until you reboot
+ your system. You may want to write a script that runs at boot-up which
+ includes the optimal settings for your system.
+
+ Setting PCI Latency Timer:
+ setpci -d 1425:* 0x0c.l=0x0000F800
+
+ Disabling TCP timestamp:
+ sysctl -w net.ipv4.tcp_timestamps=0
+
+ Disabling SACK:
+ sysctl -w net.ipv4.tcp_sack=0
+
+ Setting large number of incoming connection requests:
+ sysctl -w net.ipv4.tcp_max_syn_backlog=3000
+
+ Setting maximum receive socket buffer size:
+ sysctl -w net.core.rmem_max=1024000
+
+ Setting maximum send socket buffer size:
+ sysctl -w net.core.wmem_max=1024000
+
+ Set smp_affinity (on a multiprocessor system) to a single CPU:
+ echo 1 > /proc/irq/<interrupt_number>/smp_affinity
+
+ Setting default receive socket buffer size:
+ sysctl -w net.core.rmem_default=524287
+
+ Setting default send socket buffer size:
+ sysctl -w net.core.wmem_default=524287
+
+ Setting maximum option memory buffers:
+ sysctl -w net.core.optmem_max=524287
+
+ Setting maximum backlog (# of unprocessed packets before kernel drops):
+ sysctl -w net.core.netdev_max_backlog=300000
+
+ Setting TCP read buffers (min/default/max):
+ sysctl -w net.ipv4.tcp_rmem="10000000 10000000 10000000"
+
+ Setting TCP write buffers (min/pressure/max):
+ sysctl -w net.ipv4.tcp_wmem="10000000 10000000 10000000"
+
+ Setting TCP buffer space (min/pressure/max):
+ sysctl -w net.ipv4.tcp_mem="10000000 10000000 10000000"
+
+ TCP window size for single connections:
+ The receive buffer (RX_WINDOW) size must be at least as large as the
+ Bandwidth-Delay Product of the communication link between the sender and
+ receiver. Due to the variations of RTT, you may want to increase the buffer
+ size up to 2 times the Bandwidth-Delay Product. Reference page 289 of
+ "TCP/IP Illustrated, Volume 1, The Protocols" by W. Richard Stevens.
+ At 10Gb speeds, use the following formula:
+ RX_WINDOW >= 1.25MBytes * RTT(in milliseconds)
+ Example for RTT with 100us: RX_WINDOW = (1,250,000 * 0.1) = 125,000
+ RX_WINDOW sizes of 256KB - 512KB should be sufficient.
+ Setting the min, max, and default receive buffer (RX_WINDOW) size:
+ sysctl -w net.ipv4.tcp_rmem="<min> <default> <max>"
+
+ TCP window size for multiple connections:
+ The receive buffer (RX_WINDOW) size may be calculated the same as single
+ connections, but should be divided by the number of connections. The
+ smaller window prevents congestion and facilitates better pacing,
+ especially if/when MAC level flow control does not work well or when it is
+ not supported on the machine. Experimentation may be necessary to attain
+ the correct value. This method is provided as a starting point fot the
+ correct receive buffer size.
+ Setting the min, max, and default receive buffer (RX_WINDOW) size is
+ performed in the same manner as single connection.
+
+
+DRIVER MESSAGES
+===============
+
+ The following messages are the most common messages logged by syslog. These
+ may be found in /var/log/messages.
+
+ Driver up:
+ Chelsio Network Driver - version 2.1.1
+
+ NIC detected:
+ eth#: Chelsio N210 1x10GBaseX NIC (rev #), PCIX 133MHz/64-bit
+
+ Link up:
+ eth#: link is up at 10 Gbps, full duplex
+
+ Link down:
+ eth#: link is down
+
+
+KNOWN ISSUES
+============
+
+ These issues have been identified during testing. The following information
+ is provided as a workaround to the problem. In some cases, this problem is
+ inherent to Linux or to a particular Linux Distribution and/or hardware
+ platform.
+
+ 1. Large number of TCP retransmits on a multiprocessor (SMP) system.
+
+ On a system with multiple CPUs, the interrupt (IRQ) for the network
+ controller may be bound to more than one CPU. This will cause TCP
+ retransmits if the packet data were to be split across different CPUs
+ and re-assembled in a different order than expected.
+
+ To eliminate the TCP retransmits, set smp_affinity on the particular
+ interrupt to a single CPU. You can locate the interrupt (IRQ) used on
+ the N110/N210 by using ifconfig:
+ ifconfig <dev_name> | grep Interrupt
+ Set the smp_affinity to a single CPU:
+ echo 1 > /proc/irq/<interrupt_number>/smp_affinity
+
+ It is highly suggested that you do not run the irqbalance daemon on your
+ system, as this will change any smp_affinity setting you have applied.
+ The irqbalance daemon runs on a 10 second interval and binds interrupts
+ to the least loaded CPU determined by the daemon. To disable this daemon:
+ chkconfig --level 2345 irqbalance off
+
+ By default, some Linux distributions enable the kernel feature,
+ irqbalance, which performs the same function as the daemon. To disable
+ this feature, add the following line to your bootloader:
+ noirqbalance
+
+ Example using the Grub bootloader:
+ title Red Hat Enterprise Linux AS (2.4.21-27.ELsmp)
+ root (hd0,0)
+ kernel /vmlinuz-2.4.21-27.ELsmp ro root=/dev/hda3 noirqbalance
+ initrd /initrd-2.4.21-27.ELsmp.img
+
+ 2. After running insmod, the driver is loaded and the incorrect network
+ interface is brought up without running ifup.
+
+ When using 2.4.x kernels, including RHEL kernels, the Linux kernel
+ invokes a script named "hotplug". This script is primarily used to
+ automatically bring up USB devices when they are plugged in, however,
+ the script also attempts to automatically bring up a network interface
+ after loading the kernel module. The hotplug script does this by scanning
+ the ifcfg-eth# config files in /etc/sysconfig/network-scripts, looking
+ for HWADDR=<mac_address>.
+
+ If the hotplug script does not find the HWADDRR within any of the
+ ifcfg-eth# files, it will bring up the device with the next available
+ interface name. If this interface is already configured for a different
+ network card, your new interface will have incorrect IP address and
+ network settings.
+
+ To solve this issue, you can add the HWADDR=<mac_address> key to the
+ interface config file of your network controller.
+
+ To disable this "hotplug" feature, you may add the driver (module name)
+ to the "blacklist" file located in /etc/hotplug. It has been noted that
+ this does not work for network devices because the net.agent script
+ does not use the blacklist file. Simply remove, or rename, the net.agent
+ script located in /etc/hotplug to disable this feature.
+
+ 3. Transport Protocol (TP) hangs when running heavy multi-connection traffic
+ on an AMD Opteron system with HyperTransport PCI-X Tunnel chipset.
+
+ If your AMD Opteron system uses the AMD-8131 HyperTransport PCI-X Tunnel
+ chipset, you may experience the "133-Mhz Mode Split Completion Data
+ Corruption" bug identified by AMD while using a 133Mhz PCI-X card on the
+ bus PCI-X bus.
+
+ AMD states, "Under highly specific conditions, the AMD-8131 PCI-X Tunnel
+ can provide stale data via split completion cycles to a PCI-X card that
+ is operating at 133 Mhz", causing data corruption.
+
+ AMD's provides three workarounds for this problem, however, Chelsio
+ recommends the first option for best performance with this bug:
+
+ For 133Mhz secondary bus operation, limit the transaction length and
+ the number of outstanding transactions, via BIOS configuration
+ programming of the PCI-X card, to the following:
+
+ Data Length (bytes): 1k
+ Total allowed outstanding transactions: 2
+
+ Please refer to AMD 8131-HT/PCI-X Errata 26310 Rev 3.08 August 2004,
+ section 56, "133-MHz Mode Split Completion Data Corruption" for more
+ details with this bug and workarounds suggested by AMD.
+
+ It may be possible to work outside AMD's recommended PCI-X settings, try
+ increasing the Data Length to 2k bytes for increased performance. If you
+ have issues with these settings, please revert to the "safe" settings
+ and duplicate the problem before submitting a bug or asking for support.
+
+ NOTE: The default setting on most systems is 8 outstanding transactions
+ and 2k bytes data length.
+
+ 4. On multiprocessor systems, it has been noted that an application which
+ is handling 10Gb networking can switch between CPUs causing degraded
+ and/or unstable performance.
+
+ If running on an SMP system and taking performance measurements, it
+ is suggested you either run the latest netperf-2.4.0+ or use a binding
+ tool such as Tim Hockin's procstate utilities (runon)
+ <http://www.hockin.org/~thockin/procstate/>.
+
+ Binding netserver and netperf (or other applications) to particular
+ CPUs will have a significant difference in performance measurements.
+ You may need to experiment which CPU to bind the application to in
+ order to achieve the best performance for your system.
+
+ If you are developing an application designed for 10Gb networking,
+ please keep in mind you may want to look at kernel functions
+ sched_setaffinity & sched_getaffinity to bind your application.
+
+ If you are just running user-space applications such as ftp, telnet,
+ etc., you may want to try the runon tool provided by Tim Hockin's
+ procstate utility. You could also try binding the interface to a
+ particular CPU: runon 0 ifup eth0
+
+
+SUPPORT
+=======
+
+ If you have problems with the software or hardware, please contact our
+ customer support team via email at support@chelsio.com or check our website
+ at http://www.chelsio.com
+
+===============================================================================
+
+ Chelsio Communications
+ 370 San Aleso Ave.
+ Suite 100
+ Sunnyvale, CA 94085
+ http://www.chelsio.com
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License, version 2, as
+published by the Free Software Foundation.
+
+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.
+
+THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
+WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+
+ Copyright (c) 2003-2005 Chelsio Communications. All rights reserved.
+
+===============================================================================
diff --git a/Documentation/networking/phy.txt b/Documentation/networking/phy.txt
new file mode 100644
index 000000000000..29ccae409031
--- /dev/null
+++ b/Documentation/networking/phy.txt
@@ -0,0 +1,288 @@
+
+-------
+PHY Abstraction Layer
+(Updated 2005-07-21)
+
+Purpose
+
+ Most network devices consist of set of registers which provide an interface
+ to a MAC layer, which communicates with the physical connection through a
+ PHY. The PHY concerns itself with negotiating link parameters with the link
+ partner on the other side of the network connection (typically, an ethernet
+ cable), and provides a register interface to allow drivers to determine what
+ settings were chosen, and to configure what settings are allowed.
+
+ While these devices are distinct from the network devices, and conform to a
+ standard layout for the registers, it has been common practice to integrate
+ the PHY management code with the network driver. This has resulted in large
+ amounts of redundant code. Also, on embedded systems with multiple (and
+ sometimes quite different) ethernet controllers connected to the same
+ management bus, it is difficult to ensure safe use of the bus.
+
+ Since the PHYs are devices, and the management busses through which they are
+ accessed are, in fact, busses, the PHY Abstraction Layer treats them as such.
+ In doing so, it has these goals:
+
+ 1) Increase code-reuse
+ 2) Increase overall code-maintainability
+ 3) Speed development time for new network drivers, and for new systems
+
+ Basically, this layer is meant to provide an interface to PHY devices which
+ allows network driver writers to write as little code as possible, while
+ still providing a full feature set.
+
+The MDIO bus
+
+ Most network devices are connected to a PHY by means of a management bus.
+ Different devices use different busses (though some share common interfaces).
+ In order to take advantage of the PAL, each bus interface needs to be
+ registered as a distinct device.
+
+ 1) read and write functions must be implemented. Their prototypes are:
+
+ int write(struct mii_bus *bus, int mii_id, int regnum, u16 value);
+ int read(struct mii_bus *bus, int mii_id, int regnum);
+
+ mii_id is the address on the bus for the PHY, and regnum is the register
+ number. These functions are guaranteed not to be called from interrupt
+ time, so it is safe for them to block, waiting for an interrupt to signal
+ the operation is complete
+
+ 2) A reset function is necessary. This is used to return the bus to an
+ initialized state.
+
+ 3) A probe function is needed. This function should set up anything the bus
+ driver needs, setup the mii_bus structure, and register with the PAL using
+ mdiobus_register. Similarly, there's a remove function to undo all of
+ that (use mdiobus_unregister).
+
+ 4) Like any driver, the device_driver structure must be configured, and init
+ exit functions are used to register the driver.
+
+ 5) The bus must also be declared somewhere as a device, and registered.
+
+ As an example for how one driver implemented an mdio bus driver, see
+ drivers/net/gianfar_mii.c and arch/ppc/syslib/mpc85xx_devices.c
+
+Connecting to a PHY
+
+ Sometime during startup, the network driver needs to establish a connection
+ between the PHY device, and the network device. At this time, the PHY's bus
+ and drivers need to all have been loaded, so it is ready for the connection.
+ At this point, there are several ways to connect to the PHY:
+
+ 1) The PAL handles everything, and only calls the network driver when
+ the link state changes, so it can react.
+
+ 2) The PAL handles everything except interrupts (usually because the
+ controller has the interrupt registers).
+
+ 3) The PAL handles everything, but checks in with the driver every second,
+ allowing the network driver to react first to any changes before the PAL
+ does.
+
+ 4) The PAL serves only as a library of functions, with the network device
+ manually calling functions to update status, and configure the PHY
+
+
+Letting the PHY Abstraction Layer do Everything
+
+ If you choose option 1 (The hope is that every driver can, but to still be
+ useful to drivers that can't), connecting to the PHY is simple:
+
+ First, you need a function to react to changes in the link state. This
+ function follows this protocol:
+
+ static void adjust_link(struct net_device *dev);
+
+ Next, you need to know the device name of the PHY connected to this device.
+ The name will look something like, "phy0:0", where the first number is the
+ bus id, and the second is the PHY's address on that bus.
+
+ Now, to connect, just call this function:
+
+ phydev = phy_connect(dev, phy_name, &adjust_link, flags);
+
+ phydev is a pointer to the phy_device structure which represents the PHY. If
+ phy_connect is successful, it will return the pointer. dev, here, is the
+ pointer to your net_device. Once done, this function will have started the
+ PHY's software state machine, and registered for the PHY's interrupt, if it
+ has one. The phydev structure will be populated with information about the
+ current state, though the PHY will not yet be truly operational at this
+ point.
+
+ flags is a u32 which can optionally contain phy-specific flags.
+ This is useful if the system has put hardware restrictions on
+ the PHY/controller, of which the PHY needs to be aware.
+
+ Now just make sure that phydev->supported and phydev->advertising have any
+ values pruned from them which don't make sense for your controller (a 10/100
+ controller may be connected to a gigabit capable PHY, so you would need to
+ mask off SUPPORTED_1000baseT*). See include/linux/ethtool.h for definitions
+ for these bitfields. Note that you should not SET any bits, or the PHY may
+ get put into an unsupported state.
+
+ Lastly, once the controller is ready to handle network traffic, you call
+ phy_start(phydev). This tells the PAL that you are ready, and configures the
+ PHY to connect to the network. If you want to handle your own interrupts,
+ just set phydev->irq to PHY_IGNORE_INTERRUPT before you call phy_start.
+ Similarly, if you don't want to use interrupts, set phydev->irq to PHY_POLL.
+
+ When you want to disconnect from the network (even if just briefly), you call
+ phy_stop(phydev).
+
+Keeping Close Tabs on the PAL
+
+ It is possible that the PAL's built-in state machine needs a little help to
+ keep your network device and the PHY properly in sync. If so, you can
+ register a helper function when connecting to the PHY, which will be called
+ every second before the state machine reacts to any changes. To do this, you
+ need to manually call phy_attach() and phy_prepare_link(), and then call
+ phy_start_machine() with the second argument set to point to your special
+ handler.
+
+ Currently there are no examples of how to use this functionality, and testing
+ on it has been limited because the author does not have any drivers which use
+ it (they all use option 1). So Caveat Emptor.
+
+Doing it all yourself
+
+ There's a remote chance that the PAL's built-in state machine cannot track
+ the complex interactions between the PHY and your network device. If this is
+ so, you can simply call phy_attach(), and not call phy_start_machine or
+ phy_prepare_link(). This will mean that phydev->state is entirely yours to
+ handle (phy_start and phy_stop toggle between some of the states, so you
+ might need to avoid them).
+
+ An effort has been made to make sure that useful functionality can be
+ accessed without the state-machine running, and most of these functions are
+ descended from functions which did not interact with a complex state-machine.
+ However, again, no effort has been made so far to test running without the
+ state machine, so tryer beware.
+
+ Here is a brief rundown of the functions:
+
+ int phy_read(struct phy_device *phydev, u16 regnum);
+ int phy_write(struct phy_device *phydev, u16 regnum, u16 val);
+
+ Simple read/write primitives. They invoke the bus's read/write function
+ pointers.
+
+ void phy_print_status(struct phy_device *phydev);
+
+ A convenience function to print out the PHY status neatly.
+
+ int phy_clear_interrupt(struct phy_device *phydev);
+ int phy_config_interrupt(struct phy_device *phydev, u32 interrupts);
+
+ Clear the PHY's interrupt, and configure which ones are allowed,
+ respectively. Currently only supports all on, or all off.
+
+ int phy_enable_interrupts(struct phy_device *phydev);
+ int phy_disable_interrupts(struct phy_device *phydev);
+
+ Functions which enable/disable PHY interrupts, clearing them
+ before and after, respectively.
+
+ int phy_start_interrupts(struct phy_device *phydev);
+ int phy_stop_interrupts(struct phy_device *phydev);
+
+ Requests the IRQ for the PHY interrupts, then enables them for
+ start, or disables then frees them for stop.
+
+ struct phy_device * phy_attach(struct net_device *dev, const char *phy_id,
+ u32 flags);
+
+ Attaches a network device to a particular PHY, binding the PHY to a generic
+ driver if none was found during bus initialization. Passes in
+ any phy-specific flags as needed.
+
+ int phy_start_aneg(struct phy_device *phydev);
+
+ Using variables inside the phydev structure, either configures advertising
+ and resets autonegotiation, or disables autonegotiation, and configures
+ forced settings.
+
+ static inline int phy_read_status(struct phy_device *phydev);
+
+ Fills the phydev structure with up-to-date information about the current
+ settings in the PHY.
+
+ void phy_sanitize_settings(struct phy_device *phydev)
+
+ Resolves differences between currently desired settings, and
+ supported settings for the given PHY device. Does not make
+ the changes in the hardware, though.
+
+ int phy_ethtool_sset(struct phy_device *phydev, struct ethtool_cmd *cmd);
+ int phy_ethtool_gset(struct phy_device *phydev, struct ethtool_cmd *cmd);
+
+ Ethtool convenience functions.
+
+ int phy_mii_ioctl(struct phy_device *phydev,
+ struct mii_ioctl_data *mii_data, int cmd);
+
+ The MII ioctl. Note that this function will completely screw up the state
+ machine if you write registers like BMCR, BMSR, ADVERTISE, etc. Best to
+ use this only to write registers which are not standard, and don't set off
+ a renegotiation.
+
+
+PHY Device Drivers
+
+ With the PHY Abstraction Layer, adding support for new PHYs is
+ quite easy. In some cases, no work is required at all! However,
+ many PHYs require a little hand-holding to get up-and-running.
+
+Generic PHY driver
+
+ If the desired PHY doesn't have any errata, quirks, or special
+ features you want to support, then it may be best to not add
+ support, and let the PHY Abstraction Layer's Generic PHY Driver
+ do all of the work.
+
+Writing a PHY driver
+
+ If you do need to write a PHY driver, the first thing to do is
+ make sure it can be matched with an appropriate PHY device.
+ This is done during bus initialization by reading the device's
+ UID (stored in registers 2 and 3), then comparing it to each
+ driver's phy_id field by ANDing it with each driver's
+ phy_id_mask field. Also, it needs a name. Here's an example:
+
+ static struct phy_driver dm9161_driver = {
+ .phy_id = 0x0181b880,
+ .name = "Davicom DM9161E",
+ .phy_id_mask = 0x0ffffff0,
+ ...
+ }
+
+ Next, you need to specify what features (speed, duplex, autoneg,
+ etc) your PHY device and driver support. Most PHYs support
+ PHY_BASIC_FEATURES, but you can look in include/mii.h for other
+ features.
+
+ Each driver consists of a number of function pointers:
+
+ config_init: configures PHY into a sane state after a reset.
+ For instance, a Davicom PHY requires descrambling disabled.
+ probe: Does any setup needed by the driver
+ suspend/resume: power management
+ config_aneg: Changes the speed/duplex/negotiation settings
+ read_status: Reads the current speed/duplex/negotiation settings
+ ack_interrupt: Clear a pending interrupt
+ config_intr: Enable or disable interrupts
+ remove: Does any driver take-down
+
+ Of these, only config_aneg and read_status are required to be
+ assigned by the driver code. The rest are optional. Also, it is
+ preferred to use the generic phy driver's versions of these two
+ functions if at all possible: genphy_read_status and
+ genphy_config_aneg. If this is not possible, it is likely that
+ you only need to perform some actions before and after invoking
+ these functions, and so your functions will wrap the generic
+ ones.
+
+ Feel free to look at the Marvell, Cicada, and Davicom drivers in
+ drivers/net/phy/ for examples (the lxt and qsemi drivers have
+ not been tested as of this writing)