On Friday 23 October 2009 16:55:59 Mikulas Patocka wrote: > > On Fri, 23 Oct 2009, Bartlomiej Zolnierkiewicz wrote: > > > On Friday 23 October 2009 16:29:16 Mikulas Patocka wrote: > > > > We are through this the second time and you're still not willing > > > > neither to listen nor to read the code. We always did serialization > > > > for CMD646, we just used hwif->chipset == ide_cmd646 (without using > > > > IDE_HFLAG_SERIALIZE flag): > > > > > > > Agreed, though I wonder whether we should also provide module parameter to > > > > disable serializing on those chipsets for people not using SSDs... > > > > > > Don't do it --- disks have cache and reading from the cache is as fast as > > > reading from SSD (or even faster), so if there is some speed-race in the > > > chip, there is a possibility that the data corruption happens with disks > > > too --- just with lower probability. > > > > > > If we don't know why the chip corrupts data, we must treat it as always > > > corrupting data. > > > > I actually suspect that it is device/chipset specific interaction and not > > generic problem so adding a fallback option (w/ BIG FAT WARNING) seem to > > make sense.. > > So, why was it serialized before? I assume that either someone noticed the > corruption or someone read some datasheet noting the corruption or someone > reverse engineered some other driver and saw the serialization. Serialization is usually needed in case of chipset not handling concurrent data transfers on both ports. Unfortunately I don't know details for CMD646. > > Especially since we have never serialized on CMD643 and your patch will > > be adding performance regression without even verifying that the issue > > also affects this chipset.. > > Do you have this chip? If you were IDE maintainer, did you collect cards > with IDE chips? I recall having CMD648 and CMD649 cards somewhere, however not earlier chipsets. -- Bartlomiej Zolnierkiewicz -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
