[SCSI] isci: Fix interrupt coalescing assumption of active TCs
We always assign a dummy task context to a port in order to address a silicon issue. We have 4 ports per controller. So when idle, there are always exactly 4 TCs "active". The adaptive interrupt coalescing code uses number of active TCs to figure out the coalescing values. However, we never hit "0" TCs because of the 4 dummy TCs. Putting in fix so that we calculate this correctly. Reported-by: Dan Melnic <dan@seamicro.com> Signed-off-by: Dave Jiang <dave.jiang@intel.com> Signed-off-by: James Bottomley <JBottomley@Parallels.com>
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@ -1122,10 +1122,16 @@ void isci_host_completion_routine(unsigned long data)
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sci_controller_completion_handler(ihost);
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spin_unlock_irq(&ihost->scic_lock);
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/* the coalesence timeout doubles at each encoding step, so
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/*
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* we subtract SCI_MAX_PORTS to account for the number of dummy TCs
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* issued for hardware issue workaround
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*/
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active = isci_tci_active(ihost) - SCI_MAX_PORTS;
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/*
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* the coalesence timeout doubles at each encoding step, so
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* update it based on the ilog2 value of the outstanding requests
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*/
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active = isci_tci_active(ihost);
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writel(SMU_ICC_GEN_VAL(NUMBER, active) |
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SMU_ICC_GEN_VAL(TIMER, ISCI_COALESCE_BASE + ilog2(active)),
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&ihost->smu_registers->interrupt_coalesce_control);
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