> 1. There is no way for the 247 to see any configuration settings; > the only thing it can see are the taskfile reads and writes, and > the timing of the DMA signals from the 246. > > 2. The 246 timings for MWDMA2 and UDMA0 are identical; there is no > programming difference between these two modes. The only way the > 246 can know that UDMA is selected is by looking for the SET > FEATURES command to the drive. The 2026x certainly snoops SET FEATURES so that would be a reasonable assumption. > I've tried changing the set xfermode code to use a version of > ata_exec_internal() which doesn't return the taskfile, but this makes no > difference to the promise exploding with CRC errors with UDMA writes. > Is it possible to do a similar thing with IDENTIFY? No because you need to know if it worked. > Also, is it possible to get rid of the additional identify and read native > max address commands which seem to be repeated (command register writes > listed): You can turn off Host Protected Area support for this. You could also btw turn *on* host protected area for the IDE stack and see what occurs but I imagine its a red herring anyway. If the snoop is failing then it is more likely to be that the chip has some limitations on the taskfile snooping and perhaps requires that the device register is always written or that the registers are written in a specific order when writing the set features command. Another thing to try if that fails is using a polled set features in case the chip has problems in that area. We've seen a similar bug on some older VIA devices. -- 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
