On Mon, 2013-02-04 at 15:55 +0400, Konstantin Khlebnikov wrote: > Matthew Garrett and Alan Cox said (see LKML link below) that clearing bus-master > for all PCI devices may lead to unpredictable consequences, some devices ignores > this bit and continues DMA, some of them hang after that or crash whole system. > Probably we should leave here only warning and disable bus-mastering for each > driver individually in ->shutdown() callback. Agreed that the right place for shutting down a PCI device properly and clearing its Bus Master bit, is the driver shutdown routine, if only all drivers supplied a shutdown routine. As it is today, there are too many drivers that do not provide a shutdown routine, ata_piix, Marvell SATA driver, ATI AGP driver just to name a few among a large number of them. Yet kexec is expected to work inspite of these drivers especially since kdump depends on it. So until all PCI drivers supply a shutdown routine, this is just a band-aid to disable interrupt and Bus Master bit in pci_device_shutdown(). Most drivers do seem to supply a suspend and resume function and it was discussed many years ago if it is feasible to use the suspend() routine for drivers to shut devices down cleanly. Maybe it is time to revisit that discussion. >Cc: Khalid Aziz <khalid.aziz@xxxxxx> Please update this to khalid@xxxxxxxxxxxxxx -- Khalid -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
