[linux-dvb] Having packet corruptions with DEC2000-t and 2.4

[Sergio Moreira <sergio.moreira@gmail.com>]

I'm having problems with the v2.4 branch of the DVB drivers (pulled
today from CVS) using a Hauppauge DEC2000-t.
The device is recognized properly, and I'm able to perform a channel
scan with dvb-apps/*/scan/.
On one machine, everything works fine, but on the other I get regular
checksum errors and missing packets. The machine that doesn't work
properly is a bit under spec'ed. It has a Crusoe TM5800 clocked at
733mhz. From past experience, Crusoes are no good for performance, but
I wasn't expecting it to be this bad.

I just do a "tzap -r 'BBC ONE'", and my var/log/messages will get
constant flooding. I'm not even reading any data from dvr0, just
running tzap. I modified ttusb_dec.c a little, to print out the first
4 bytes of each packet. Looking at the log messages, sometimes some
packets will start with "00 00" instead of the usual 0x47 Sync byte.
Whenever there is a checksum error, one packet seems to go missing.

I've patched ttusb_dec.c like this:

        for (i = 0; i < dec->packet_length; i += 2)
                csum ^= ((dec->packet[i] << 8) + dec->packet[i + 1]);

Here ->        printk("%02x %02x %02x %02x\n", dec->packet[0],
dec->packet[1], dec->packet[2], dec->packet[3]);
        if (csum) {
                printk("%s: checksum failed - discarding\n", __FUNCTION__);
                return;
        }

Any insight on whether it could be a software problem that I could
solve on my side, or some setting/tweaking I could do on the hardware,
or does it look like the machine is just too slow to keep up with the
USB data ?

Thanks for any info/tip...

Sergio
---

I've put a sample of my var/log/messages at
http://www.nagworld.org/dvb/var-log-sample.txt

Result of /sbin/lspci of the non working machine:

00:00.0 Host bridge: Transmeta Corporation LongRun Northbridge (rev 01)
00:00.1 RAM memory: Transmeta Corporation SDRAM controller
00:00.2 RAM memory: Transmeta Corporation BIOS scratchpad
00:06.0 Multimedia audio controller: ALi Corporation M5451 PCI AC-Link
Controller Audio Device (rev 02)
00:07.0 ISA bridge: ALi Corporation M1533 PCI to ISA Bridge [Aladdin IV]
00:08.0 Modem: ALi Corporation Intel 537 [M5457 AC-Link Modem]
00:09.0 FireWire (IEEE 1394): Texas Instruments TSB43AA22 IEEE-1394
Controller (PHY/Link Integrated) (rev 02)
00:0a.0 Multimedia controller: Citicorp TTI: Unknown device 2011
00:0b.0 Ethernet controller: Realtek Semiconductor Co., Ltd.
RTL-8139/8139C/8139C+ (rev 10)
00:0c.0 VGA compatible controller: ATI Technologies Inc Radeon Mobility M6 LY
00:0f.0 USB Controller: ALi Corporation USB 1.1 Controller (rev 03)
00:10.0 IDE interface: ALi Corporation M5229 IDE (rev c4)
00:11.0 Non-VGA unclassified device: ALi Corporation M7101 PMU
00:12.0 CardBus bridge: Ricoh Co Ltd RL5c475 (rev 80)
00:14.0 USB Controller: ALi Corporation USB 1.1 Controller (rev 03)

model name      : Transmeta(tm) Crusoe(tm) Processor TM5800
cpu MHz         : 727.810
cache size      : 512 KB