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[SCSI] isci: Fix interrupt coalescing assumption of active TCs

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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>
This commit is contained in:
Dave Jiang 2012-09-05 16:35:44 -07:00 committed by James Bottomley
parent 54b4667775
commit 44ef2bf72d
1 changed files with 8 additions and 2 deletions
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10
drivers/scsi/isci/host.c
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@ -1122,10 +1122,16 @@ void isci_host_completion_routine(unsigned long data)
sci_controller_completion_handler(ihost);
spin_unlock_irq(&ihost->scic_lock);
/* the coalesence timeout doubles at each encoding step, so
/*
* we subtract SCI_MAX_PORTS to account for the number of dummy TCs
* issued for hardware issue workaround
*/
active = isci_tci_active(ihost) - SCI_MAX_PORTS;
/*
* the coalesence timeout doubles at each encoding step, so
* update it based on the ilog2 value of the outstanding requests
*/
active = isci_tci_active(ihost);
writel(SMU_ICC_GEN_VAL(NUMBER, active) |
SMU_ICC_GEN_VAL(TIMER, ISCI_COALESCE_BASE + ilog2(active)),
&ihost->smu_registers->interrupt_coalesce_control);