Hello, Jeff, Linus. Jeff Garzik wrote: > Linus Torvalds wrote: >> >> On Fri, 1 Jun 2007, Jeff Garzik wrote: >>> With these old PATA devices, device reset is "six of one, half-dozen >>> of the >>> other." Using SRST is the only way to kick some ATAPI devices into >>> working: >>> http://suif.stanford.edu/~csapuntz/blackmagic.html#reset >> >> Well, wouldn't it be a good thing to >> 1) if BUSY/DRQ is set even before you try the problem, obviously skip >> the two polite cases, and go to #4 >> 2) try to just do an IDENTIFY 3) if that doesn't work, do a HOST >> RESET and then try again >> 4) if that doesn't work, do the full SRST >> >> (or some variation of the above). > > Skipping reset means it doesn't get the device away from a state that > the previous boot may have configured itself to... standard "I didn't do > reset" problems you see with any hardware. Transfer modes and > removeable media status notification are the most notable that are left > in a semi-random state, but there are many other minor feature bits that > fall into this category as well. libata configures most of the stuff, so I don't think we'll see big surprises even if we skip SRST during probing but I agree that it's nice to give good kicks in the devices' asses during probing. We can try IDENTIFY/IDENTIFY_PACKET with short timeout first and then issue reset if the device isn't in reset blacklist, but it would make probe sequence.... IDENTIFY -> reset -> IDENTIFY -> configure -> IDENTIFY for reval Which doesn't seem too attractive. We can use the result from the first IDENTIFY for configuration but it's probably a good idea to re-read IDENTIFY page after reset. It would be best if we can handle these braindead SRST-impaired devices in the common code, if that's not feasible, we should at least provide some option to allow correct (without timeout) detection of these devices. Thanks. -- tejun - 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
