> Are you assuming that a device driver will use an iochk_read() for > every DMA operation? for every MMIO to the card? > > For high performance devices, it seems to me that this will cause > a rather large performance burden, especially if its envisioned that > all architectures will do something similar. > > My concern is that (at least on ppc64) the call pci_read_config_word() > requires a call into "firmware" aka "BIOS", which takes thousands upon > thousands of cpu cycles. There are hundreds of cycles of gratuitous > crud just to get into the firmware, and then lord-knows-what the > firmware does while its in there; probably doing all sorts of crazy > math to compute bus addresses and other arcane things. I would imagine > that most architectures, includig ia64, are similar. > > Thus, one wouldn't want to perform an iochk_read() in this way unless > one was already pretty sure that an error had already occured ... > > Am I misunderstanding something?
I would expect pSeries not to use the "default" error checking (that tests the status register) but rather use EEH. Ben. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
