[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>
diff --git a/drivers/scsi/isci/host.c b/drivers/scsi/isci/host.c
index d4daa0f..ab026a5 100644
--- a/drivers/scsi/isci/host.c
+++ b/drivers/scsi/isci/host.c
@@ -1122,10 +1122,16 @@
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);