Dear list, We have made a new board based upon the DM6446 but struggle with what seems to be some internal timing problems when communicating with optical drives. Linux kernel debugging is however not our expertise and wonder if someone might have a clue what's going on. Currently using Montavista 4.0 (kernel 2.6.10 based), but I have also tested with the GIT 2.6.20 kernel with the same results.
We have added some debug strings from various places in the ATA drivers and from this we have found that some ATA commands work just fine, but others fail (like cdrom_get_disc_info()), typically hanging on "wait_for_completion(&wait);" in ide-io.c. This leads to timeouts and kernel messages like "hda: lost interrupt" Also, different disks, depending on the data on the disk or if blank will cause the different hangs. However! I found that when compiling the kernel with the option "System type and features->Preemption Mode->No forced preemption mode(Server)" set makes things work much smoother than the default "Preemptible Kernel (Low-Latency Desktop)", but still not 100%. We can write and mount DVDs usually without failures. So obviously something timing related. Important to note that we communicate with SATA DVD drives (tried different types/brands) through a Marvell 88SA8040 ATA<->SATA host bridge. And that communication through this bridge leads to problems. Things seems to work fine with normal optical ATA devices. Also tried a bridge from Jmicron but same problems. The results are also the same on the EVM. By the way, we have not observed any problems with SATA HDDs through the bridge. We feel 99% confident there's no hardware ATA/SATA bus related problem since different HDDs work fine on the same interface and in different modes, and we've done extensive measurements regarding signal integrity. So we feel there's something about ATAPI drivers and timing when going through this bridge. So, very happy for suggestions about potential problems or advice for further debugging. Thanks! (sorry if this message comes twice, some mailing problems here..) _______________________________________________ Davinci-linux-open-source mailing list [email protected] http://linux.davincidsp.com/mailman/listinfo/davinci-linux-open-source
