From aa6083ed50957f699596999affbb6eb9d7a8b72e Mon Sep 17 00:00:00 2001 From: Vineet Gupta Date: Fri, 7 Nov 2014 10:45:28 +0530 Subject: ARCv2: SMP: ARConnect debug/robustness - Handle possible interrupt coalescing from MCIP - chk if prev IPI ack before sending new Signed-off-by: Vineet Gupta --- arch/arc/kernel/mcip.c | 48 ++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 44 insertions(+), 4 deletions(-) (limited to 'arch/arc/kernel/mcip.c') diff --git a/arch/arc/kernel/mcip.c b/arch/arc/kernel/mcip.c index e6ad6e64440a..35921c3ab394 100644 --- a/arch/arc/kernel/mcip.c +++ b/arch/arc/kernel/mcip.c @@ -33,27 +33,67 @@ void mcip_init_smp(unsigned int cpu) static void mcip_ipi_send(int cpu) { unsigned long flags; + int ipi_was_pending; + + /* + * NOTE: We must spin here if the other cpu hasn't yet + * serviced a previous message. This can burn lots + * of time, but we MUST follows this protocol or + * ipi messages can be lost!!! + * Also, we must release the lock in this loop because + * the other side may get to this same loop and not + * be able to ack -- thus causing deadlock. + */ + + do { + raw_spin_lock_irqsave(&mcip_lock, flags); + __mcip_cmd(CMD_INTRPT_READ_STATUS, cpu); + ipi_was_pending = read_aux_reg(ARC_REG_MCIP_READBACK); + if (ipi_was_pending == 0) + break; /* break out but keep lock */ + raw_spin_unlock_irqrestore(&mcip_lock, flags); + } while (1); - raw_spin_lock_irqsave(&mcip_lock, flags); __mcip_cmd(CMD_INTRPT_GENERATE_IRQ, cpu); raw_spin_unlock_irqrestore(&mcip_lock, flags); + +#ifdef CONFIG_ARC_IPI_DBG + if (ipi_was_pending) + pr_info("IPI ACK delayed from cpu %d\n", cpu); +#endif } static void mcip_ipi_clear(int irq) { - unsigned int cpu; + unsigned int cpu, c; unsigned long flags; + unsigned int __maybe_unused copy; raw_spin_lock_irqsave(&mcip_lock, flags); /* Who sent the IPI */ __mcip_cmd(CMD_INTRPT_CHECK_SOURCE, 0); - cpu = read_aux_reg(ARC_REG_MCIP_READBACK); /* 1,2,4,8... */ + copy = cpu = read_aux_reg(ARC_REG_MCIP_READBACK); /* 1,2,4,8... */ - __mcip_cmd(CMD_INTRPT_GENERATE_ACK, __ffs(cpu)); /* 0,1,2,3... */ + /* + * In rare case, multiple concurrent IPIs sent to same target can + * possibly be coalesced by MCIP into 1 asserted IRQ, so @cpus can be + * "vectored" (multiple bits sets) as opposed to typical single bit + */ + do { + c = __ffs(cpu); /* 0,1,2,3 */ + __mcip_cmd(CMD_INTRPT_GENERATE_ACK, c); + cpu &= ~(1U << c); + } while (cpu); raw_spin_unlock_irqrestore(&mcip_lock, flags); + +#ifdef CONFIG_ARC_IPI_DBG + if (c != __ffs(copy)) + pr_info("IPIs from %x coalesced to %x\n", + copy, raw_smp_processor_id()); +#endif } volatile int wake_flag; -- cgit v1.2.3