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Date: Sat, 19 May 2007 14:22:15 -0400 From: "Albert Cahalan" <acahalan@...il.com> To: "Segher Boessenkool" <segher@...nel.crashing.org> Cc: tglx@...utronix.de, "Sergei Shtylyov" <sshtylyov@...mvista.com>, linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org Subject: Re: [PATCH 2.6.21-rt2] PowerPC: decrementer clockevent driver On 5/19/07, Segher Boessenkool <segher@...nel.crashing.org> wrote: > [Albert Cahalan] > > Set MMCR0[TBEE], set MMCR0[PMXE], and choose a TBL bit via > > MMCR0[TBSEL]. > > That's the performance monitor, which could very well be > in use already (for performance monitoring stuff, who > would have guessed). It is the performance monitor, which sadly can not be used very well unless the decrementer is disabled. The hardware is buggy. As long as we use the decrementer for timekeeping, we can not safely generate performance monitor interrupts. I'd like to have the performance monitor available. It's NOT available unless we use part of it for timekeeping. That's the choice the hardware gives us. We can get TBL bit flip interrupts for free. We don't even need to give up one of the event counters. If we do give up one of the event counters (a rather reasonable idea), then we can count one of those TBL bit flips or the cycle counter. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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