I wrote: > Question to others: > > ohci1394.c::ohci_irq_handler() is taking a per-host spinlock around some > register reads and writes, particularly: > ... > spin_lock_irqsave(&ohci->event_lock, flags); > event = reg_read(ohci, OHCI1394_IntEventClear); > reg_write(ohci, OHCI1394_IntEventClear, event & > ~OHCI1394_busReset); > spin_unlock_irqrestore(&ohci->event_lock, flags); > ... > spin_lock_irqsave(&ohci->event_lock, flags); > reg_write(ohci, OHCI1394_IntMaskClear, OHCI1394_busReset); > run_an_insane_loop_as_an_alleged_fix_for_dorky_hardware; > spin_unlock_irqrestore(&ohci->event_lock, flags); > ... > spin_lock_irqsave(&ohci->event_lock, flags); > reg_write(ohci, OHCI1394_IntEventClear, OHCI1394_busReset); > reg_write(ohci, OHCI1394_IntMaskSet, OHCI1394_busReset); > spin_unlock_irqrestore(&ohci->event_lock, flags); > > I think these spinlocks are totally useless 1. because > ohci_irq_handler() is only called as the hardware interrupt servicing > routine and 2. because they don't flush the register write operations. > Right? Wrong? [Ohci1394's reg_write() is a writel().]
Also, what is the status of ordering guarantees --- or lack thereof --- for writel() under Linux 2.6.16 and 2.6.18? Especially in presence of a PCI-X to PCI bridge... -- Stefan Richter -=====-=-==- =-== ==-== http://arcgraph.de/sr/ - 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/
