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Date: Tue, 27 Jan 2015 21:45:55 +0000 From: James Hogan <james.hogan@...tec.com> To: Ralf Baechle <ralf@...ux-mips.org>, <linux-mips@...ux-mips.org> CC: <linux-kernel@...r.kernel.org>, James Hogan <james.hogan@...tec.com> Subject: [PATCH 9/9] MIPS: Allow shared IRQ for timer & perf counter Before release 2 of the architecture there weren't separate interrupt pending bits for the local CPU interrupts (timer & perf counter overflow), so when they were connected to the same interrupt line the timer handler had to call the performance counter handler before knowing whether a timer interrupt was actually pending. Now another CPU local interrupt, for the Fast Debug Channel (FDC), can also be routed to an arbitrary interrupt line. It isn't scalable to keep adding cross-calls between handlers for these cases of shared interrupt lines, especially since the FDC could in theory share its interrupt line with the performance counter, timer, or both. Fortunately since release 2 of the architecture separate interrupt pending bits do exist in the Cause register. This allows local interrupts which share an interrupt line to have separate handlers using IRQF_SHARED. Unfortunately they can't easily have their own irqchip as there is no generic way to individually mask them. Enable this sharing to happen by removing the special case for when the perf count shares an IRQ with the timer. cp0_perfcount_irq and cp0_compare_irq can then be set to the same value with shared interrupt handlers registered for both of them. Pre-R2 code should be unaffected. cp0_perfcount_irq will always be -1 and the timer handler will contnue to call into the perf counter handler. Signed-off-by: James Hogan <james.hogan@...tec.com> Cc: Ralf Baechle <ralf@...ux-mips.org> Cc: linux-mips@...ux-mips.org --- arch/mips/kernel/traps.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c index ad3d2031c327..9c109fd8ba99 100644 --- a/arch/mips/kernel/traps.c +++ b/arch/mips/kernel/traps.c @@ -2006,8 +2006,6 @@ void per_cpu_trap_init(bool is_boot_cpu) cp0_compare_irq_shift = CAUSEB_TI - CAUSEB_IP; cp0_compare_irq = (read_c0_intctl() >> INTCTLB_IPTI) & 7; cp0_perfcount_irq = (read_c0_intctl() >> INTCTLB_IPPCI) & 7; - if (cp0_perfcount_irq == cp0_compare_irq) - cp0_perfcount_irq = -1; } else { cp0_compare_irq = CP0_LEGACY_COMPARE_IRQ; cp0_compare_irq_shift = CP0_LEGACY_PERFCNT_IRQ; -- 2.0.5 -- 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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