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On 11-12-07 14:50, David Newall wrote: > Rene Herman wrote: >> This particular discussion isn't about anything in general but solely >> about the delay an outb_p gives you on x86 since what is under >> discussion is not using an output to port 0x80 on that platform to >> generate it. > > That could be true if outb_p were used only in architecture dependent It not only could be, it _is_ true. Not using an output to port 0x80 is what this discussion is about. > code, but it's not. It's used in drivers that are supposed to run on > all sorts of platforms. Why does a megaraid controller need delays on > i386 but not on Sparc, PowerPC, Alpha and others? Is it buggy on most > platforms, or just unnecessarily slow on Intel? The latter probably and I don't bleedin' well care. In a discussion about removing the out to 0x80 the only thing that is relevant is what it should be replaced with. Usually, "nothing" will do but generally, udelay(1) will. >>> is needed, wouldn't you use a real delay; one that says how long it >>> should be? >> Thinking that _p gives a pause is perhaps too PC-centric. Why, if a delay >> >> Because any possible outb_p delay should be synced to the bus-clock, >> not to any wall-clock. > > You misunderstand. A delay can be counted in bus cycles. No damnit, you misunderstand. I'm saying that an outb_p _should_ be defined in terms of the bus clock since if you want a wall-clock delay you should be using just that. The _hardware_ is synced to the bus clock and therefore, having a delay available that is synced to the bus clock as well makes some sense. And again again again again not withstanding that, a udelay will still be an okay replacement in practice. Rene. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | |||||||||
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