On 2 Dec 2002, Nat Ersoz wrote:
> I'm debugging a problem in the natsemi.c driver which has the symptom
> that muticast reception quits for no apparent reason.
This is very likely a receiver reset that clears the hash table.
Note: I've updated the natsemi.c driver three times in the past three
months. You might want to look at the changes.
> Unicast still works fine, the multicast stream is being sent, but no
> packets make it past the hash filter. In versions of the driver,
> 2.4.19 and before, we "fixed" this problem by setting ifconfig
> "allmuti" on the device.
A poor solution. If the chip has a broken filter (see the epic100
driver) the driver should handle the flaw based on the chip version.
If a driver isn't calculating the hash table correctly, you can work
around the problem for that driver only by setting the module option
multicast_filter_limit=0
> As I'm writing a debug routine, I notice that:
> static void __set_rx_mode(struct net_device *dev)
> {
> ...
>
> for (i = 0, mclist = dev->mc_list;
> mclist && i < dev->mc_count;
> i++, mclist = mclist->next) {
> set_bit_le(
> dp83815_crc(ETH_ALEN, mclist->dmi_addr) & 0x1ff,
> mc_filter); /* WHOOPS!! Shouldn't this be &mc_filter[i*2]
> ?? */
No. See what set_bit() (and set_bit_le() in this case) does. It works
on a bit arry and handles any byte arithmetic/shifting internally.
The dp83815 chip is quirky:
the filter index is a byte address,
the filter entries must be written as pairs of bytes
the filter entry write must be a 32 bit operation.
You may note that the natsemi.c driver in the kernel does not write
registers using the correct bit width.
Keep in mind: it's clear that the dp83815 designers were trying to do
big-endian design on a little-endian bus. Do not expect that code for
the superficially similar dp83820 will work on the dp83815!
--
Donald Becker becker@scyld.com
Scyld Computing Corporation http://www.scyld.com
410 Severn Ave. Suite 210 Scyld Beowulf cluster system
Annapolis MD 21403 410-990-9993
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