From 4a91d8fb61e2b5218acc7a46d5dd28ff1f44f927 Mon Sep 17 00:00:00 2001 From: James Hogan Date: Tue, 27 Jan 2015 21:45:55 +0000 Subject: [PATCH] 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 Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/9131/ Signed-off-by: Ralf Baechle --- 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 33984c04b60b..424567cfeb3d 100644 --- a/arch/mips/kernel/traps.c +++ b/arch/mips/kernel/traps.c @@ -2055,8 +2055,6 @@ 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; -- 2.20.1