Commit Graph

82 Commits

Author SHA1 Message Date
Florin Malita 93c1d3b790 spidernet: skb used after netif_receive_skb
The stats update code in spider_net_pass_skb_up() is touching the skb
after it's been passed up to the stack. To avoid that, just update the
stats first.

Signed-off-by: Florin Malita <fmalita@gmail.com>
Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-05-24 17:25:43 -04:00
Christoph Hellwig 98739407c5 spidernet: node-aware skbuff allocation
Spidernet was the driver I original did all the node-aware netdevice
allocation for, but after a year it still hasn't hit mainline.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-05-17 20:43:15 -04:00
Ishizaki Kou a1c38a4a5d spidernet: remove unnecessary accesses to phy
This patch removes unnecessary accesses to phy registers.

Signed-off-by: Kou Ishizaki <kou.ishizaki@toshiba.co.jp>
Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-05-11 17:53:13 -04:00
Stephen Rothwell 40cd3a4564 [POWERPC] Rename get_property to of_get_property: drivers
These are all the remaining instances of get_property.  Simple rename of
get_property to of_get_property.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>
2007-05-02 20:04:32 +10:00
Arnaldo Carvalho de Melo eddc9ec53b [SK_BUFF]: Introduce ip_hdr(), remove skb->nh.iph
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2007-04-25 22:25:10 -07:00
Arnaldo Carvalho de Melo 4c13eb6657 [ETH]: Make eth_type_trans set skb->dev like the other *_type_trans
One less thing for drivers writers to worry about.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2007-04-25 22:24:30 -07:00
Linas Vepstas 33bdeec806 spidernet: Fix problem sending IP fragments
The basic structure of "normal" UDP/IP/Ethernet
frames (that actually work):
 - It starts with the Ethernet header (dest MAC, src MAC, etc.)
 - The next part is occupied by the IP header (version info, length of
packet, id=0, fragment offset=0, checksum, from / to address, etc.)
 - Then comes the UDP header (src / dest port, length, checksum)
 - Actual payload
 - Ethernet checksum

Now what's different for IP fragment:
 - The IP header has id set to some value (same for all fragments),
offset is set appropriately (i.e. 0 for first fragment, following
according to size of other fragments), size is the length of the frame.
 - UDP header is unchanged. I.e. length is according to full UDP
datagram, not just the part within the actual frame! But this is only
true within the first frame: all following frames don't have a valid
UDP-header at all.

The spidernet silicon seems to be quite intelligent: It's able to
compute (IP / UDP / Ethernet) checksums on the fly and tests if frames
are conforming to RFC -- at least conforming to RFC on complete frames.

But IP fragments are different as explained above:
I.e. for IP fragments containing part of a UDP datagram it sees
incompatible length in the headers for IP and UDP in the first frame
and, thus, skips this frame. But the content *is* correct for IP
fragments. For all following frames it finds (most probably) no valid
UDP header at all. But this *is* also correct for IP fragments.

The Linux IP-stack seems to be clever in this point. It expects the
spidernet to calculate the checksum (since the module claims to be able
to do so) and marks the skb's for "normal" frames accordingly
(ip_summed set to CHECKSUM_HW).
But for the IP fragments it does not expect the driver to be capable to
handle the frames appropriately. Thus all checksums are allready
computed. This is also flaged within the skb (ip_summed set to
CHECKSUM_NONE).

Unfortunately the spidernet driver ignores that hints. It tries to send
the IP fragments of UDP datagrams as normal UDP/IP frames. Since they
have different structure the silicon detects them the be not
"well-formed" and skips them.

The following one-liner against 2.6.21-rc2 changes this behavior. If the
IP-stack claims to have done the checksumming, the driver should not
try to checksum (and analyze) the frame but send it as is.

Signed-off-by: Norbert Eicker <n.eicker@fz-juelich.de>
Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-04-19 15:01:16 -04:00
Linas Vepstas 7376e73256 spidernet: janitorial, typos
Janitorial patch. Undo long lines, fix typo in err msg.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: Jens Osterkamp <Jens.Osterkamp@de.ibm.com>
Cc: Kou Ishizaki <kou.ishizaki@toshiba.co.jp>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-27 04:16:03 -05:00
Linas Vepstas 5c8e98fe47 spidernet: transmit race
Multiple threads performing a transmit can race into
the spidernet tx ring cleanup code. This puts the
relevant check under a lock.

Signed-off-by: Linas Vepstas <lins@austin.ibm.com>
Cc: Jens Osterkamp <Jens.Osterkamp@de.ibm.com>
Cc: Kou Ishizaki <kou.ishizaki@toshiba.co.jp>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-27 04:16:03 -05:00
Linas Vepstas d9c199ee78 spidernet: fix racy double-free of skb
It appears that under certain circumstances, a race will result
in a double-free of an skb. This patch null's out the skb pointer
upon the skb free, avoiding the inadvertent deref of bogus data.
The next patch fixes the actual race.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: Jens Osterkamp <Jens.Osterkamp@de.ibm.com>
Cc: Kou Ishizaki <kou.ishizaki@toshiba.co.jp>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-27 04:16:03 -05:00
Linas Vepstas 4cb6f9e57d spidernet: separate hardware state from driver state.
This patch separates the hardware descriptor state from the
driver descriptor state, per (old) suggestion from Ben Herrenschmidt.
This compiles and boots and seems to work.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: Jens Osterkamp <Jens.Osterkamp@de.ibm.com>
Cc: Kou Ishizaki <kou.ishizaki@toshiba.co.jp>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-27 04:16:03 -05:00
Jens Osterkamp 4b23a554db spidernet: move medium variable into card struct
This moves the medium variable into the spidernet card structure.
It renames the GMII_ variables to BCM54XX specific ones.

Signed-off-by: Jens Osterkamp <jens@de.ibm.com>
Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-27 04:16:03 -05:00
Ishizaki Kou fc8e13da91 spidernet: remove txram full logging
This patches removes logging for SPIDER_NET_GTMFLLINT interrupts.
Since the interrupts are not irregular, and they happen frequently
when using 100Mbps network switches.

Signed-off-by: Kou Ishizaki <kou.ishizaki@toshiba.co.jp>
Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-27 04:16:03 -05:00
Kou Ishizaki 3342cf0e59 spidernet: spidernet: add support for Celleb
This patch adds or changes some HW specific settings for spider_net on
Celleb.

Signed-off-by: Kou Ishizaki <kou.ishizaki@toshiba.co.jp>
Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-27 04:16:03 -05:00
Kou Ishizaki 3cf761ddcc spidernet: load firmware when open
This patch moves calling init_firmware() from spider_net_probe() to
spider_net_open() so as to use the driver by built-in.

Signed-off-by: Kou Ishizaki <kou.ishizaki@toshiba.co.jp>
Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-27 04:16:03 -05:00
Kou Ishizaki abdb66b566 spidernet: autoneg support for Celleb
Add auto negotiation support for Celleb.

Signed-off-by: Kou Ishizaki <kou.ishizaki@toshiba.co.jp>
Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-27 04:16:02 -05:00
Linas Vepstas d406eafee8 spidernet: compile break.
As of 2.6.20-git4, the spider_net driver does not compile.
This appears to be due to some archaic usage involving kobjects.

It also fixes a nasty double-free during ifdown of the interface.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: Jens Osterkamp <Jens.Osterkamp@de.ibm.com>
Cc: Kou Ishizaki <kou.ishizaki@toshiba.co.jp>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-27 04:16:02 -05:00
Al Viro 97210b5f1c [PATCH] spider_net breakage from class_device -> device
Acked-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-09 08:28:48 -08:00
Linas Vepstas d9a9720eab Spidernet: Rework RX linked list
Make the hardware perceive the RX descriptor ring as a null-terminated linked
list, instead of a circular ring.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-07 18:48:56 -05:00
Linas Vepstas 6d24998f07 Spidernet RX Debugging printout
Add some debugging and error printing.

The show_rx_chain() prints out the status of the rx chain,
which shows that the status of the descriptors gets
messed up after the second & subsequent RX ramfulls.

Print out contents of bad packets if error occurs.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-05 16:58:45 -05:00
Linas Vepstas df519ab2c5 Spidernet Avoid possible RX chain corruption
Delete possible source of chain corruption; the hardware
already knows the location of the tail, and writing it
again is likely to mess it up.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-05 16:58:45 -05:00
Linas Vepstas 90476a20fa Spidernet Memory barrier
Add memory barrier to make sure that the rest of the
RX descriptor state is flushed to memory before we tell
the hardware that its ready to go.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-05 16:58:45 -05:00
Linas Vepstas 2c307db7e4 Spidernet RX Chain tail
Tell the hardware the location of the rx ring tail.
More punctuation cleanup.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-05 16:58:44 -05:00
Linas Vepstas a4182c50bc Spidernet Remove unused variable
Remove unused variable; this makes code easier to read.
Tweak commentary.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-05 16:58:44 -05:00
Linas Vepstas 80dab7c7e5 Spidernet RX Refill
The invocation of the rx ring refill routine is haphazard,
it can be called from a central location.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-05 16:58:44 -05:00
Linas Vepstas 7f7223b8f1 Spidernet Cleanup return codes
Simplify the somewhat convoluted use of return codes
in the rx buffer handling.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-05 16:58:44 -05:00
Linas Vepstas 366684bd0d Spidernet another skb mem leak
Another skb leak in an error branch. Fix this by adding
call to dev_kfree_skb_irq() after moving to a more
appropriate spot.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-05 16:58:44 -05:00
Linas Vepstas 05b346b552 Spidernet RX skb mem leak
One of the unlikely error branches has an skb memory leak.
Fix this by handling the error conditions consistently.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-05 16:58:44 -05:00
Linas Vepstas 1cd173f66c Spidernet cleanup un-needed API
There is no need to pass a flag into spider_net_decode_one_descr()
so remove this, and perform some othre minor cleanup.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-05 16:58:44 -05:00
Linas Vepstas 75856175c2 Spidernet remove rxramfull tasklet
Get rid of the rxramfull tasklet, and let the NAPI poll routine
deal with this situation. (The rxramfull interrupt is simply
stating that the h/w has run out of room for incoming packets).

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-05 16:58:44 -05:00
Linas Vepstas 5a028877d2 Spidernet add net_ratelimit to suppress long output
This patch adds net_ratelimit to many of the printks in order to
limit extraneous warning messages (created in response to Bug 28554).
This patch supercedes all previous ratelimit patches.
This has been tested, please apply.

From: James K Lewis <jklewis@us.ibm.com>
Signed-off-by: James K Lewis <jklewis@us.ibm.com>
Signed-off-by: Linas Vepstas <jlinas@austin.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-05 16:58:44 -05:00
Linas Vepstas d4ed8f8d1f Spidernet DMA coalescing
The current driver code performs 512 DMA mappings of a bunch of
32-byte ring descriptor structures. This is silly, as they are
all in contiguous memory. This patch changes the code to
dma_map_coherent() each rx/tx ring as a whole.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-05 16:58:43 -05:00
Jens Osterkamp a55eb05a57 spidernet : fix memory leak in spider_net_stop
We forget to call spider_net_free_rx_chain_contents which does the
actual dev_kfree_skb. New skbs are allocated from skbuff_head_cache
on each "ifconfig up" letting the cache grow infinitely.

This patch fixes it.

Signed-off-by: Jens Osterkamp <jens@de.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2007-02-02 08:34:10 -05:00
David Howells 9db7372445 Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6
Conflicts:

	drivers/ata/libata-scsi.c
	include/linux/libata.h

Futher merge of Linus's head and compilation fixups.

Signed-Off-By: David Howells <dhowells@redhat.com>
2006-12-05 17:01:28 +00:00
David Howells 4c1ac1b491 Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6
Conflicts:

	drivers/infiniband/core/iwcm.c
	drivers/net/chelsio/cxgb2.c
	drivers/net/wireless/bcm43xx/bcm43xx_main.c
	drivers/net/wireless/prism54/islpci_eth.c
	drivers/usb/core/hub.h
	drivers/usb/input/hid-core.c
	net/core/netpoll.c

Fix up merge failures with Linus's head and fix new compilation failures.

Signed-Off-By: David Howells <dhowells@redhat.com>
2006-12-05 14:37:56 +00:00
Benjamin Herrenschmidt 3bc0f40c28 [POWERPC] Spider uses low level BE MMIO accessors
We use the powerpc specific low level MMIO accessor variants instead
of readl() or readl_be() because we know spidernet is not a real PCI
device and we can thus avoid the performance hit caused by the PCI
workarounds.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
2006-12-04 20:38:55 +11:00
Linas Vepstas 7bd54c8636 [PATCH] spidernet: poor network performance
Correct a problem seen on later kernels running the NetPIPE application.
Specifically, NetPIPE would begin running very slowly at the 1533 packet
size.  It was determined that Spidernet slowed with an idle DMA engine.

Signed-off-by: James K Lewis <jklewis@us.ibm.com>
Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2006-11-30 06:14:06 -05:00
James K Lewis 9c434f5e21 [PATCH] Spidernet: remove ETH_ZLEN check in earlier patch
In an earlier patch, code was added to pad packets that were less that
ETH_ZLEN (60) bytes using the skb_pad function.  This has caused hangs when
accessing certain NFS mounted file systems.  This patch removes the check
and solves the NFS problem.  The driver, with this patch, has been tested
extensively.  Please apply.

Signed-off-by: James K Lewis <jklewis@us.ibm.com>
Cc: Stephen Hemminger <shemminger@osdl.org>
Cc: Jeff Garzik <jgarzik@pobox.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2006-11-30 06:14:06 -05:00
David Howells c4028958b6 WorkStruct: make allyesconfig
Fix up for make allyesconfig.

Signed-Off-By: David Howells <dhowells@redhat.com>
2006-11-22 14:57:56 +00:00
Linas Vepstas 6475191001 [PATCH] powerpc/cell spidernet release all descrs
Bugfix: rx descriptor release function fails to visit
the last entry while walking receive descriptor ring.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2006-10-11 04:04:27 -04:00
Linas Vepstas 348bc2a6e3 [PATCH] powerpc/cell spidernet DMA direction fix
The ring buffer descriptors are DMA-accessed bidirectionally,
but are not declared in this way.  Fix this.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2006-10-11 04:04:27 -04:00
Linas Vepstas 66c097165c [PATCH] powerpc/cell spidernet variable name change
Cosmetic patch: give the variable holding the numer of descriptors
a more descriptive name, so to avoid confusion.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2006-10-11 04:04:27 -04:00
Linas Vepstas a664ccf430 [PATCH] powerpc/cell spidernet reduce DMA kicking
The current code attempts to start the TX dma every time a packet
is queued. This is too conservative, and wastes CPU time. This
patch changes behaviour to call the kick-dma function less often,
only when the tx queue is at risk of emptying.

This reduces cpu usage, improves performance.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2006-10-11 04:04:26 -04:00
Linas Vepstas 499eea1872 [PATCH] powerpc/cell spidernet
Remove a dummy register read that is not needed.
This reduces CPU usage notably during transmit.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: James K Lewis <jklewis@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2006-10-11 04:04:26 -04:00
Linas Vepstas 9cc7bf7edf [PATCH] powerpc/cell spidernet refine locking
The transmit side of the spider ethernet driver currently
places locks around some very large chunks of code. This
results in a fair amount of lock contention is some cases.
This patch makes the locks much more fine-grained, protecting
only the cirtical sections. One lock is used to protect
three locations: the queue head and tail pointers, and the
queue low-watermark location.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: James K Lewis <jklewis@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2006-10-11 04:04:26 -04:00
Linas Vepstas 68a8c609b3 [PATCH] powerpc/cell spidernet NAPI polling info.
This patch moves transmit queue cleanup code out of the
interrupt context, and into the NAPI polling routine.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: James K Lewis <jklewis@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2006-10-11 04:04:26 -04:00
Linas Vepstas 204e5fa17c [PATCH] powerpc/cell spidernet low watermark patch.
Implement basic low-watermark support for the transmit queue.
Hardware low-watermarks allow a properly configured kernel
to continously stream data to a device and not have to handle
any interrupts at all in doing so. Correct zero-interrupt
operation can be actually observed for this driver, when the
socket buffer is made large enough.

The basic idea of a low-watermark interrupt is as follows.
The device driver queues up a bunch of packets for the hardware
to transmit, and then kicks the hardware to get it started.
As the hardware drains the queue of pending, untransmitted
packets, the device driver will want to know when the queue
is almost empty, so that it can queue some more packets.

If the queue drains down to the low waterark, then an interrupt
will be generated. However, if the kernel/driver continues
to add enough packets to keep the queue partially filled,
no interrupt will actually be generated, and the hardware
can continue streaming packets indefinitely in this mode.

The impelmentation is done by setting the DESCR_TXDESFLG flag
in one of the packets. When the hardware sees this flag, it will
interrupt the device driver. Because this flag is on a fixed
packet, rather than at  fixed location in the queue, the
code below needs to move the flag as more packets are
queued up. This implementation attempts to keep the flag
at about 1/4 from "empty".

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Signed-off-by: James K Lewis <jklewis@us.ibm.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2006-10-11 04:04:26 -04:00
Linas Vepstas b21606a773 [PATCH] powerpc/cell spidernet incorrect offset
Bugfix -- the rx chain is in memory after the tx chain --
the offset being used was wrong, resulting in memory corruption
when the size of the rx and tx rings weren't exactly the same.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2006-10-11 04:04:26 -04:00
Linas Vepstas 98b9040c74 [PATCH] powerpc/cell spidernet stop error printing patch.
Turn off mis-interpretation of the queue-empty interrupt
status bit as an error.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Signed-off-by: James K Lewis <jklewis@us.ibm.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2006-10-11 04:04:26 -04:00
Linas Vepstas 37aad7500b [PATCH] powerpc/cell spidernet fix error interrupt print
The print message associated with the descriptor chain end interrupt
prints a bogs value. Fix that.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: James K Lewis <jklewis@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
2006-10-11 04:04:26 -04:00