-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Am Thursday 28 August 2003 18:44 schrieben Sie: > I might be talking cross purposes, but I had a full featured DVB-T card > which I could never get stable in a variety of systems. > > However, In my P4 system I have had a lot of corrupt and distorted data > transfers (which I don't get in my P3 system) with a budget Nova-T card. > In *my* case the Nova-T driver was trying to use quite aggressive PCI burst > settings and it appeared the motherboard could just not cope. I had to > completely back down the bursting to single dwords before I got something > which was stable.
Hi, I have similar problems like Andreas and we discussed them on a thread on the vdr mailing-list. I supposed these to be a problem with PCI transfers on intel 845 chipsets and the Nova-S cards, seems like this can be confirmed. My first attempt was a look into the specs, http://www.semiconductors.philips.com/acrobat/datasheets/SAA7146A_1.pdf Page 31 describes transfer mode settings. I have taken a look in the dvb kernel sources (2.6.0-test4) and found some commands regarding PCI transfers (drivers/media/dvb/ttpci/budget-core.c): start_ts_capture() { saa7146_write(dev, PCI_BT_V1, 0x001c0000 | (saa7146_read(dev, PCI_BT_V1) & ~0x001f0000)); } ttpci_budget_init() { saa7146_write(dev, PCI_BT_V1, 0x001c0000); } I suppose that the latter is executed first. I don't know why it is written again during capture, but if nothing else changes the value, it should stay at 0x001c0000. In a resent posting I have found following snippet: (http://www.linuxtv.org/mailinglists/linux-dvb/2003/08-2003/msg00248.html) - ------------------------------------------------------------------------------------------ FWIW, these are exactly the symptoms I had on a SIS chipset with a budget card. These cards appear to be very timing sensitive. The parameters to play with are the SAA7146A "FIFO threshold" and "PCI burst length" settings. Settings I found to work well: 1. PCI burst = 32 DWORDs, FIFO threshold = 32 DWORDs - This one handles even a 40Mbps DVB-Cable stream on both i440BX as well as i850E chipsets (don't have others to try). 2. PCI burst = 16 DWORDs, FIFO threshold = 16 DWORDs - seems to work equally well. 3. PCI burst = 16 DWORDs, FIFO threshold = 32 DWORDs - The only setting which allowed me to make a DVB-T budget card work on a SIS 651 chipset. - ------------------------------------------------------------------------------------------ At last, I have some questions left: - - What DMA channel is used on a budget card? It seems to be channel 3, but I have no proof for this. - - Why are the recommended values for channel 3 32 Dwords Threshold and 16 Dwords burst? - - Is anyone using different values? I will try some combinations this evening and post the results. bye, Stefan -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.2 (GNU/Linux) iD8DBQE/Tzk//bI7T1LKTh8RAtSHAJ4vQ+o9WsDfVlGNVKaonpISYwtlSQCfbGcu R/aI2s+CQoC+bIeTkkNXr0w= =pXhV -----END PGP SIGNATURE----- -- Info: To unsubscribe send a mail to [EMAIL PROTECTED] with "unsubscribe linux-dvb" as subject.
