asks that each buffer be (2048 * 256) bytes long. I suspect that alignment
isn't a real requirement since busdma only recently started honoring it. The
size is also bogus. Fix both of these and stop busdma from trying to
exhaust the system memory pool with bounce pages.
Submitted by: Kevin Oberman
MFC After: 7 days
is a no-op on little endian architectures, but fixes getting the MAC
address for some dc(4) cards on big endian architectures.
This is a RELENG_5 candidate.
Tested by: gallatin (powerpc), marius (sparc64)
First version of the patch written by: gallatin
by default. As such, mark if_dc as IFF_NEEDSGIANT until such
time as appropriate locking review and testing can take place,
and the locking can be enabled by default.
RELENG_5 candidate.
variable. If set to "true" OF_getetheraddr() will now return the unique
MAC address stored in the "local-mac-address" property of the device's
OFW node if present and the host address/system default MAC address if
the node doesn't doesn't have such a property. If set to "false" the
host address will be returned for all devices like before this change.
This brings the behaviour of device drivers for NICs with OFW support/
FCode, i.e. dc(4) for on-board DM9102A on Sun machines, gem(4) and hme(4),
regarding "local-mac-address?" in line with NetBSD and Solaris.
The man pages of the respective drivers will be updated separately to
reflect this change.
- Remove OF_getetheraddr2() which was used as a stopgap in dc(4). Its
functionality is now part of OF_getetheraddr().
the falling edge of a media state change.
This is in preparation for media state change notification to the
routing socket.
No objections by: sam, wpaul, ru, bms
Brucification by: bde
MAC address in the EEPROM, and we need to get it from OpenFirmware.
This isn't very pretty but time is lacking to do this in a better
way this near 5.2-RELEASE. This is a RELENG_5_2 candidate.
Original version by: Marius Strobl <marius@alchemy.franken.de>
Tested by: Pete Bentley <pete@sorted.org>
Reviewed by: jake
frame, not the first. It is probably also not safe to free the mbuf chain
as soon as the OWN bit is cleared on the first descriptor since the chip
may not be done copying the frame into the transmit FIFO. Revert the part of
of busdma conversion (if_dc.c rev 1.115) which changed dc_txeof() to look for
the status in the first descriptor and free the mbuf chain when processing
the first descriptor for the frame, and revert the matching changes elsewhere
in the driver. This part of the busdma change caused the driver to report
spurious collisions and output errors, even when running in full-duplex mode.
Reverting the mbuf chain handling slightly complicates dc_dma_map_txbuf(),
since it is responsible for setting the OWN bits on the descriptors, but does
not normally have direct access to the mbuf chain.
Tested by:
Dejan Lesjak <dejan.lesjak at ijs.si> alpha/<Intel 21143 10/100BaseTX>
"Xin LI" <delphij at frontfree.net> i386/<Macronix 98713 10/100BaseTX>
Wiktor Niesiobedzki <bsd at w.evip.pl> i386/<3Com OfficeConnect 10/100B>
Reviewed by: mux
this problem put these lines back in. While they should be
unnecessary, they appear to be sometimes necessary.
Reviewed in concept: dfr
Approved by: re (scottl@)
the packets are immediately returned for sending (e.g. when bridging
or packet forwarding). There are more efficient ways to do this
but for now use the least intrusive approach.
Reviewed by: imp, rwatson
multicast hash are written. There are still two distinct algorithms used,
and there actually isn't any reason each driver should have its own copy
of this function as they could all share one copy of it (if it grew an
additional argument).
to the pci attachment. Cardbus is a derived class of pci so all pci
drivers are automatically available for matching against cardbus devices.
Reviewed by: imp
if_xname, if_dname, and if_dunit. if_xname is the name of the interface
and if_dname/unit are the driver name and instance.
This change paves the way for interface renaming and enhanced pseudo
device creation and configuration symantics.
Approved By: re (in principle)
Reviewed By: njl, imp
Tested On: i386, amd64, sparc64
Obtained From: NetBSD (if_xname)
chain passed into dc_encap, which dc_start was unaware of. This caused
the old (now invalid) mbuf to be passed to BPF_MTAP.
Spotted by: Kenjiro Cho <kjc@csl.sony.co.jp>
for 21143 based cards which use SIA mode.
This fixes 10mbit mode for ZNYX ZX346Q cards and other
21143 based cards.
PR: 32118
Submitted by: Rene de Vries <rene@tunix.nl>
Geert Jan de Groot <GeertJan.deGroot@tunix.nl>
Obtained from: BSDI
MFC after: 2 weeks
that has been recorded earlier and overwrite it again later by
reading it directly from the EEPROM again.
Read the MAC address from the PAR0/PAR1 registers instead, which
are autoloaded on reboot.
Tested on AN985, AN983B. According to the datasheets, it should
also work for the AL981 (I don't have such a chip on a card at home)
PR: 52988
Submitted by: Andrew Gordon <arg-bsd@arg.me.uk>
MFC after: 2 weeks
- MN-110 10/100 USB ethernet (ADMtek Pegasus II, if_aue)
- MN-120 10/100 cardbus (ADMtek Centaur-C, if_dc)
- MN-130 10/100 PCI (ADMtek Centaur-P, if_dc)
Also update dc(4) man page to mention support for MN-120 and MN-130.
to have this driver working on sparc64. It still needs to be made
endian-clean before it can work there.
Special thanks to dragonk@evilcode.net for sending me a dc(4) card so
that I was able to do this work.
Many cheers to all the people that tested this change, thanks to them,
this change shouldn't break anything :-).
Tested by: marcel (i386 and ia64), ru (i386), wilko (alpha),
mbr (i386), wpaul (i386) and
Will Saxon <WillS@housing.ufl.edu> (i386)
forced to do slightly bogus power state manipulation. However, this
is one of those features that is preventing further progress, so mark
them as BURN_BIRDGES like I did for the drivers in sys/dev/...
This, like the other change, are a no-op unless you have BURN_BRIDGES
in your kernel.
bzero(ptr, sizeof(DC_RXLEN * 5));
which should obviously be:
bzero(ptr, DC_RXLEN * 5);
Looks like this bug may have reduced the effectiveness of the
workaround for the hardware bug in the PNIC chips.
MFC after: 1 week
o Remove register keyword
o ANSIfy prototypes
o Remove "return;" at the end of void functions
o Remove trailing spaces
o Don't align local variables with tabs and reorder them
o Don't use /* FOO */ at the end of a #ifdef FOO block if
it's a small block
- Other non-functional changes :
o 6 -> ETHER_ADDR_LEN
o Don't initialize if_output; ether_ifattach() does it for us
The submitter of PR 32118 told me that this patch also fixes autoselecting
for znyx 4 port cards (10baseT, 100baseTX did work already).
PR: 32118
Reviewed by: imp
Approved by: rwatson (re)
if attach succeeded. device_is_alive just tells us that probe
succeeded. Since we were using it to do things like detach net
interfaces, this caused problems when there were errors in the attach
routine.
Symptoms of problem reported by: martin blapp
- Unconditionally call *_stop() if device is in the tree. This is to
prevent callouts from happening after the device is gone. Checks for
bus_child_present() should be added in the future to keep from touching
potentially non-existent hardware in *_detach(). Found by iedowse@.
- Always check for and free miibus children, even if the device is not in
the tree since some failure cases could have gotten here.
- Call ether_ifdetach() in the irq setup failure case
- ti(4), xl(4): move ifmedia_init() calls to the beginning of attach so
that ifmedia_removeall() can be unconditionally called on detach. There
is no way to detect whether ifmedia has been initialized without using
a separate variable (as tl(4) does).
- Add comments to indicate assumptions of code path
in dc_detach() instead of only calling it if the hardware is preset.
This is a workaround for page faults in softclock() after a `dc'
device was detached, caused by not disabling a timer before freeing
its memory. The bus_child_present() checks should probably be
re-added later, but only to avoid the hardware accesses and not the
other resource cleanups in dc_stop().
Approved by: njl
network layer (ether).
- Don't abuse module names to facilitate ifconfig module loading;
such abuse isn't really needed. (And if we do need type information
associated with a module then we should make it explicit and not
use hacks.)
- Remove locking of the softc in the attach method, instead depending on
bus_setup_intr being at the end of attach (delaying interrupt enable until
after ether_ifattach is called)
- Call *_detach directly in the error case of attach, depending on checking
in detach to only free resources that were allocated. This puts all
resource freeing in one place, avoiding thinkos that lead to memory leaks.
- Add bus_child_present check to calls to *_stop in the detach method to
be sure hw is present before touching its registers.
- Remove bzero softc calls since device_t should do this for us.
- dc: move interrupt allocation back where it was before. It was unnecessary
to move it. This reverts part of 1.88
- rl: move irq allocation before ether_ifattach. Problems might have been
caused by allocating the irq after enabling interrupts on the card.
- rl: call rl_stop before ether_ifdetach
- sf: call sf_stop before ether_ifdetach
- sis: add missed free of sis_tag
- sis: check errors from tag creation
- sis: move dmamem_alloc and dmamap_load to happen at same time as tag creation
- sk: remove duplicate initialization of sk_dev
- ste: add missed bus_generic_detach
- ti: call ti_stop before ether_ifdetach
- ti: add missed error setting in ti_rdata alloc failure
- vr: add missed error setting in I/O, memory mapping cases
- xl: add missed error setting in I/O, memory mapping cases
- xl: remove multi-level goto on attach failure
- xl: move dmamem_alloc and dmamap_load to happen at same time as tag creation
- Calls to free(9) are unconditional because it is valid to call free with a
null pointer.
Reviewed by: imp, mdodd
function.
Also, use m_defrag where appropriate to defrag long mbuf chains
in the same fashion as was done in if_sis.c. Before this change,
if_dc would blow up and take down the interface if fed a really long
mbuf chain.
MFC after: 2 weeks
and ether_ifattach() to end. This fixes a "could sleep" case and
simplifies error exit cases as well. Also be sure to set errno
and clean up resources in !mac error case.
Tested by: Ryan Beasley
pci_get_ether accesor, which gets it from the CIS for cardbus cards
(and from other pci-like buses via whatever mechanism is used there).
Submitted by: sam
Approved by: re (blanket)
o use if_input for input packet processing
o don't strip the Ethernet header for input packets
o use BPF_* macros bpf tapping
o call ether_ioctl to handle default ioctl case
o track vlan changes
Reviewed by: many
Approved by: re
OpenBSD who got the code (or the idea) from the NetBSD tlp driver.
This gets some cardbus dc cards working (either completely or nearly
so). It also appears to get additional pci cards working, without
breaking working ones.
# Maybe some additional work is needed here. Also, the cardbus attachment
# might need to match on the CIS rather than on the vendor/device so we have
# a finer level of detail as to what the card is. Technically, the
# vendor/device fields are undefined for CardBus (even though most cards are
# using common silicon with pci models).
RXSTATE to STOPPED, but to WAIT. This should fix hangs which
could only be solved by replugging the cable.
Submitted by: jhb
Reviewed by: phk
MFC after: 2 weeks
This is temporary hack, better and generalized solution probably
should be implemented at lower layer(MII or PCI?).
Tested by: shoko.araki@soliton.co.jp
MFC after: 1 week
Rename mii_phy_auto_stop() mii_phy_down().
Introduce mii_down(), use it from nge. Do not indirect it to 19 identical
case's in 19 switchstatements like NetBSD did.
Rev 1.56 of if_dc.c removed calls to mii_pollstat() from the dc_tick()
routine. dc_tick() is called regularly to detect link up and link down
status, especially when autonegotiating.
The expectation was that mii_tick() (which is still called from dc_tick())
would update status information automatically in all cases where it would
be sensible to do so.
Unfortunately, with authentic 21143 chips this is not the case, and
the driver never successfully autonegotiates. This is because (despite
what it says in the 21143 manual) the chip always claims that link is not
present while the autonegotiation enable bit is set. Autonegotation takes
place and succeeds, but the driver tests the link bits before it switches
off the autonegotiation enable bit, and success is not recognised.
The simplest solution is to call dcphy_status() more often for MII_TICK
calls by dropping out of the switch statement instead of exiting when
we are autonegotiating and link appears to not be present. When
autonegotiation succeeds, dcphy_status() will note the speed and fdx/hdx
state and turn off the autonegotiation enable bit. The next call to
dcphy_status() will notice that link is present, and the dc driver code
will be notified.
Macronix chips also use this code, but implement link detection as
described in the manual, and hence don't need this patch. However, tests
on a Macronix 98715AEC-C show that it does not adversely affect them.
This could be done better but is the minimal effective change, and most
closely mimics what was happening prior to rev 1.56 of if_dc.c. (Actually
I also deleted a small amount of unnecessary code while I was in the area.)
Reviewed by: wpaul
most cases NULL is passed, but in some cases such as network driver locks
(which use the MTX_NETWORK_LOCK macro) and UMA zone locks, a name is used.
Tested on: i386, alpha, sparc64
One to notify the system that the MTU for VLAN can be 1500 so the vlan
will automatically be configured with a 1500 MTU the other is to ignore
the error case if the received frame is to long.
The frame size notification came from code in the SIS driver, and
the support for long frames derived from the NetBSD Tulip driver.
Tested on: 4 port D-Link adapter DFE-570TX 4 Intel 21143
Netgear card with 82c169 PNIC 10/100BaseTX
Reviewed by: ru (manpage), wpaul (not objected to), archie
Approved by: imp
Obtained from: NetBSD
to Phil Kernick:
"The problem is that in full duplex mode, the Conexant chip always reports a
carrier lost error, even when the frame is successfully sent. So, if we
have a Conexant chip, then ignore carrier lost when in full duplex
mode."
Since the Xircom chips seem to have the same issue and since we already
have a workaround for this, just expand the workaround test to also
check for DC_IS_CONEXANT().
to a label is inside an #ifdef block, then the label should *also* be
inside an #ifdef block. Hide the "done:" label which is only used if
DEVICE_POLLING is enabled under #ifdef DEVICE_POLLING.
Non-SMP, i386-only, no polling in the idle loop at the moment.
To use this code you must compile a kernel with
options DEVICE_POLLING
and at runtime enable polling with
sysctl kern.polling.enable=1
The percentage of CPU reserved to userland can be set with
sysctl kern.polling.user_frac=NN (default is 50)
while the remainder is used by polling device drivers and netisr's.
These are the only two variables that you should need to touch. There
are a few more parameters in kern.polling but the default values
are adequate for all purposes. See the code in kern_poll.c for
more details on them.
Polling in the idle loop will be implemented shortly by introducing
a kernel thread which does the job. Until then, the amount of CPU
dedicated to polling will never exceed (100-user_frac).
The equivalent (actually, better) code for -stable is at
http://info.iet.unipi.it/~luigi/polling/
and also supports polling in the idle loop.
NOTE to Alpha developers:
There is really nothing in this code that is i386-specific.
If you move the 2 lines supporting the new option from
sys/conf/{files,options}.i386 to sys/conf/{files,options} I am
pretty sure that this should work on the Alpha as well, just that
I do not have a suitable test box to try it. If someone feels like
trying it, I would appreciate it.
NOTE to other developers:
sure some things could be done better, and as always I am open to
constructive criticism, which a few of you have already given and
I greatly appreciated.
However, before proposing radical architectural changes, please
take some time to possibly try out this code, or at the very least
read the comments in kern_poll.c, especially re. the reason why I
am using a soft netisr and cannot (I believe) replace it with a
simple timeout.
Quick description of files touched by this commit:
sys/conf/files.i386
new file kern/kern_poll.c
sys/conf/options.i386
new option
sys/i386/i386/trap.c
poll in trap (disabled by default)
sys/kern/kern_clock.c
initialization and hardclock hooks.
sys/kern/kern_intr.c
minor swi_net changes
sys/kern/kern_poll.c
the bulk of the code.
sys/net/if.h
new flag
sys/net/if_var.h
declaration for functions used in device drivers.
sys/net/netisr.h
NETISR_POLL
sys/dev/fxp/if_fxp.c
sys/dev/fxp/if_fxpvar.h
sys/pci/if_dc.c
sys/pci/if_dcreg.h
sys/pci/if_sis.c
sys/pci/if_sisreg.h
device driver modifications
Introduce an additional device flag for those NICs which require the
transmit buffers to be aligned to 32-bit boundaries.
(the equivalen fix for STABLE is slightly simpler because there are
no supported chips which require this alignment there.)
The reason we are required to commit to -current first is so that later
MFC's do not risk the loss of existing bug fixes. Even if this was not
strictly required in -current, it should still be fixed there too.
mbuf allocation fails, and fix (i hope) a couple of style bugs.
I believe these printf() are extremely dangerous because now they can
occur on every incoming packet and are not rate limited. They were
meant to warn the sysadmin about lack of resources, but now they
can become a nice way to panic your system under load.
Other drivers (e.g. the fxp driver) have nothing like this.
There is a pending discussion on putting this kind of warnings
elsewhere, and I hope we can fix this soon.
underlying unaligned bcopy) on incoming packets that are already
available (albeit unaligned) in a buffer.
The performance improvement varies, depending on CPU and memory
speed, but can be quite large especially on slow CPUs. I have seen
over 50% increase on forwarding speed on the sis driver for the
486/133 (embedded systems), which does exactly the same thing.
The behaviour is controlled by a sysctl variable, hw.dc_quick which
defaults to 1. Set it to 0 to restore the old behaviour.
After running a few experiments (in userland, though) I am convinced
that doing the m_devget() is detrimental to performance in almost
all cases.
Even if your CPU has degraded performance with misaligned data,
the bcopy() in the driver has the same overhead due to misaligment
as the one that you save in the uiomove(), plus you do one extra
copy and pollute the cache.
But more often than not, you do not even have to touch the payload,
e.g. when you are forwarding packets, and even in the often-cited
case of NFS, you often end up passing a pointer to the payload to
the disk controller.
In any case, you can play with the sysctl variable to toggle between
the two behaviours, and see if it makes a difference.
MFC-after: 3 days
in the 21143, instead of giving priority to the receive unit.
This gives a 10-15% performance improvement in the forwarding rate
under heavy load.
Reviewed-by: Bill Paul
. Make internal service routines static.
. Use a consistent ordering of checks in MII_TICK. Do the work in the
mii_phy_tick() subroutine if appropriate.
. Call mii_phy_update() to trigger the callbacks.
laptops with this chip should test this and report back as I don't have
access to this hardware myself. People with -stable systems should try
the patch at:
http://www.freebsd.org/~wpaul/conexant.patch.gz
Submitted by: Phil Kernick <Phil@Kernick.org>
a bunch of frames. In this case, the dc_link flag is cleared, and dc_start()
stops draining the if_snd send queue, which results in lots of 'no buffers
available' errors being reported to applications. The whole idea behind
not draining the send queue until the link comes up was to avoid having
the gratuitous ARP being lost while we're waiting for autoneg to complete
after the interface is first brought up. As an optimization, change the
test in dc_start() so that we only bail if dc_link is not set _and_ there
are less than 10 packets in the send queue. If the queue has many frames
in it, we need to drain them. If the queue has a small number of frames
in it, we can hold off on sending them until the link comes up.
MFC after: 1 week
something: offset into the first mbuf of the target chain before copying
the source data over.
Make drivers using m_devget() with a first argument "data - ETHER_ALIGN"
to use the offset argument to pass ETHER_ALIGN in. The way it was previously
done is potentially dangerous if the source data was at the top of a page
and the offset caused the previous page to be copied (if the
previous page has not yet been appropriately mapped).
The old `offset' argument in m_devget() is not used anywhere (it's always
0) and dates back to ~1995 (and earlier?) when support for ethernet trailers
existed. With that support gone, it was merely collecting dust.
Tested on alpha by: jlemon
Partially submitted by: jlemon
Reviewed by: jlemon
MFC after: 3 weeks
- Use pci_get_powerstate()/pci_set_powerstate() in all the other drivers
that need them so we don't have to fiddle with the PCI power management
registers directly.
- Use pci_enable_busmaster()/pci_enable_io() to turn on busmastering and
PIO/memory mapped accesses.
- Add support to the RealTek driver for the D-Link DFE-530TX+ which has
a RealTek 8139 with its own PCI ID. (Submitted by Jason Wright)
- Have the SiS 900/National DP83815 driver be sure to disable PME
mode in sis_reset(). This apparently fixes a problem on some
motherboards where the DP83815 chip fails to receive packets.
(Submitted by Chuck McCrobie <mccrobie@cablespeed.com>)
case there is nothing to do. This happens normally when the card shares
the interrupt line with other devices.
This code saves a couple of microseconds per interrupt even on a
fast CPU. You normally would not care, except under heavy tinygram
traffic where you can have some 50-100.000 interrupts per second...
On passing, correct a spelling error.
mtx_enter(lock, type) becomes:
mtx_lock(lock) for sleep locks (MTX_DEF-initialized locks)
mtx_lock_spin(lock) for spin locks (MTX_SPIN-initialized)
similarily, for releasing a lock, we now have:
mtx_unlock(lock) for MTX_DEF and mtx_unlock_spin(lock) for MTX_SPIN.
We change the caller interface for the two different types of locks
because the semantics are entirely different for each case, and this
makes it explicitly clear and, at the same time, it rids us of the
extra `type' argument.
The enter->lock and exit->unlock change has been made with the idea
that we're "locking data" and not "entering locked code" in mind.
Further, remove all additional "flags" previously passed to the
lock acquire/release routines with the exception of two:
MTX_QUIET and MTX_NOSWITCH
The functionality of these flags is preserved and they can be passed
to the lock/unlock routines by calling the corresponding wrappers:
mtx_{lock, unlock}_flags(lock, flag(s)) and
mtx_{lock, unlock}_spin_flags(lock, flag(s)) for MTX_DEF and MTX_SPIN
locks, respectively.
Re-inline some lock acq/rel code; in the sleep lock case, we only
inline the _obtain_lock()s in order to ensure that the inlined code
fits into a cache line. In the spin lock case, we inline recursion and
actually only perform a function call if we need to spin. This change
has been made with the idea that we generally tend to avoid spin locks
and that also the spin locks that we do have and are heavily used
(i.e. sched_lock) do recurse, and therefore in an effort to reduce
function call overhead for some architectures (such as alpha), we
inline recursion for this case.
Create a new malloc type for the witness code and retire from using
the M_DEV type. The new type is called M_WITNESS and is only declared
if WITNESS is enabled.
Begin cleaning up some machdep/mutex.h code - specifically updated the
"optimized" inlined code in alpha/mutex.h and wrote MTX_LOCK_SPIN
and MTX_UNLOCK_SPIN asm macros for the i386/mutex.h as we presently
need those.
Finally, caught up to the interface changes in all sys code.
Contributors: jake, jhb, jasone (in no particular order)
if_vr: handle the case where vr_encap() returns failure: bust out of the
packet sending loop instead of panicking. Also add some missing
newlines to some printf()s.
if_dc: The miibus_read and miibus_write methods keep swapping in and
out of MII mode by fiddling with CSR6 for cards with MII PHYs.
This is a hack to support the original Macronix 98713 card which
has built-in NWAY that uses an MII-like management interface
even though it uses serial transceivers. Conditionalize this
so that we only do this on 98713 chips, since it does bad things
to genuine tulip chips (and maybe other clones).
All calls to mtx_init() for mutexes that recurse must now include
the MTX_RECURSE bit in the flag argument variable. This change is in
preparation for an upcoming (further) mutex API cleanup.
The witness code will call panic() if a lock is found to recurse but
the MTX_RECURSE bit was not set during the lock's initialization.
The old MTX_RECURSE "state" bit (in mtx_lock) has been renamed to
MTX_RECURSED, which is more appropriate given its meaning.
The following locks have been made "recursive," thus far:
eventhandler, Giant, callout, sched_lock, possibly some others declared
in the architecture-specific code, all of the network card driver locks
in pci/, as well as some other locks in dev/ stuff that I've found to
be recursive.
Reviewed by: jhb
PCI code. This saves each driver from having to grovel around looking
for the right registers to twiddle.
I should eventually convert the other PCI drivers to do this; for now,
these three are ones which I know need power state handling.
the interface to use callout_* instead of timeout(). Also add an
IS_MPSAFE #define (currently off) which will mark the driver as mpsafe
to the upper layers.
them. If we leave garbage in them, the dc_apply_fixup() routine may
try to follow bogus pointers when applying the reset fixup.
Noticed by: Andrew Gallatin
a RealTek 8139 cardbus device. Unfortunately it doesn't quite work yet
because the CIS parser barfs on it.
Submitted by msmith, with some small tweaks by me.
the PCI latency timer value to 0x80. Davicom's Linux driver does this,
and it drastically reduces the number of TX underruns in my tests. (Note:
this is done only for the Davicom chips. I'm not sure it's a good idea to
do it for all of them.)
Again, still waiting on confirmation before merging to stable.
DM9100/DM9102 chips. Do not set DC_TX_ONE. The DC_TX_USE_TX_INTR flag
causes dc_encap() to set the 'interrupt on TX completion' bit only
once every 64 packets. This is an attempt to reduce the number
of interrupts generated by the chip. You're supposed to get a 'no more
TX buffers left' interrupt once you hit the last packet whether you
ask for one or not, however it seems the Davicom chip doesn't generate
this interrupt, or at least it doesn't generate it under the same
circumstances. The result is that if you transmit n packets, where
n is less than 64, and then wait 5 seconds, you'll get a watchdog
timeout whether you want one or not. The DC_TX_INTR_ALWAYS causes
dc_encap() to request an interrupt for every frame.
I'm still waiting on confirmation from a couple of users to see if this
fixes their problems with the Davicom DM9102 before I merge this into
-stable, but this fixed the problem for me in my own testing so I'm
willing to make the change to -current right away.
