scsi: hisi_sas: Default enable interrupt coalescing

In the current interrupt reporting mode, each CQ entry reports an
interrupt. However, when there are a large number of I/O hardware
completion interrupts, the following issue may occur:

[ 4682.678657][  C129] irq 134: nobody cared (try booting with the "irqpoll" option)
[ 4682.708455][  C129] Call trace:
[ 4682.711589][  C129]  dump_backtrace+0x0/0x1e4
[ 4682.715934][  C129]  show_stack+0x20/0x2c
[ 4682.719933][  C129]  dump_stack+0xd8/0x140
[ 4682.724017][  C129]  __report_bad_irq+0x54/0x180
[ 4682.728625][  C129]  note_interrupt+0x1ec/0x2f0
[ 4682.733143][  C129]  handle_irq_event+0x118/0x1ac
[ 4682.737834][  C129]  handle_fasteoi_irq+0xc8/0x200
[ 4682.742613][  C129]  __handle_domain_irq+0x84/0xf0
[ 4682.747391][  C129]  gic_handle_irq+0x88/0x2c0
[ 4682.751822][  C129]  el1_irq+0xbc/0x140
[ 4682.755648][  C129]  _find_next_bit.constprop.0+0x20/0x94
[ 4682.761036][  C129]  cpumask_next+0x24/0x30
[ 4682.765208][  C129]  gic_ipi_send_mask+0x48/0x170
[ 4682.769900][  C129]  __ipi_send_mask+0x34/0x110
[ 4682.775720][  C129]  smp_cross_call+0x3c/0xcc
[ 4682.780064][  C129]  arch_send_call_function_single_ipi+0x38/0x44
[ 4682.786146][  C129]  send_call_function_single_ipi+0xd0/0xe0
[ 4682.791794][  C129]  generic_exec_single+0xb4/0x170
[ 4682.796659][  C129]  smp_call_function_single_async+0x2c/0x40
[ 4682.802395][  C129]  blk_mq_complete_request_remote.part.0+0xec/0x100
[ 4682.808822][  C129]  blk_mq_complete_request+0x30/0x70
[ 4682.813950][  C129]  scsi_mq_done+0x48/0xac
[ 4682.818128][  C129]  sas_scsi_task_done+0xb0/0x150 [libsas]
[ 4682.823692][  C129]  slot_complete_v3_hw+0x230/0x710 [hisi_sas_v3_hw]
[ 4682.830120][  C129]  cq_thread_v3_hw+0xbc/0x190 [hisi_sas_v3_hw]
[ 4682.836114][  C129]  irq_thread_fn+0x34/0xa4
[ 4682.840371][  C129]  irq_thread+0xc4/0x130
[ 4682.844455][  C129]  kthread+0x108/0x13c
[ 4682.848365][  C129]  ret_from_fork+0x10/0x18
[ 4682.852621][  C129] handlers:
[ 4682.855577][  C129] [<00000000949e52bf>] cq_interrupt_v3_hw [hisi_sas_v3_hw] threaded [<000000005d8e3b68>] cq_thread_v3_hw [hisi_sas_v3_hw]
[ 4682.868084][  C129] Disabling IRQ torvalds#134

When the IRQ management layer processes each hardware interrupt, if the
return value of the interrupt handler is IRQ_WAKE_THREAD, it will wake up
the handler thread for this interrupt action and set IRQTF_RUNTHREAD flag,
wait for the interrupt handling thread to clear the IRQTF_RUNTHREAD flag
after execution. Later in note_interrupt(), use irq_count to count
hardware interrupts and irqs_unhandled to count interrupts for which no
thread handler is responsible. When irq_count reaches 100000 and
irqs_unhandled reaches 99000, irq will be disabled.

In the performance test scenario, I/O completion hardware interrupts are
continuously and quickly generated. As a result, the interrupt processing
thread is cyclically called in irq_thread() and does not exit, this
affects the response of the interrupt thread to the hardware interrupt and
causes irqs_unhandled to grow to 99000. Finally, the irq is disabled.

Therefore, default enable interrupt coalescing to reduce the generation of
hardware interrupts, this helps interrupt processing threads to stop
calling in irq_thread().

For interrupt coalescing, according to the actual performance test, set
the count of CQ entries to 10 and the interrupt coalescing timeout period
to 10us based on the actual performance test.

Before and after interrupt coalescing is enabled, the 4K read/write
performance is improved by about 3%, and the 256K read/write performance
is basically the same.

Signed-off-by: Yihang Li <[email protected]>
Reviewed-by: Xiang Chen <[email protected]>

drivers/scsi/hisi_sas/hisi_sas_v3_hw.c

@@ -638,9 +638,11 @@ static void init_reg_v3_hw(struct hisi_hba *hisi_hba)
 	hisi_sas_write32(hisi_hba, TRANS_LOCK_ICT_TIME, 0x4A817C80);
 	hisi_sas_write32(hisi_hba, HGC_SAS_TXFAIL_RETRY_CTRL, 0x108);
 	hisi_sas_write32(hisi_hba, CFG_AGING_TIME, 0x1);
-	hisi_sas_write32(hisi_hba, INT_COAL_EN, 0x1);
-	hisi_sas_write32(hisi_hba, OQ_INT_COAL_TIME, 0x1);
-	hisi_sas_write32(hisi_hba, OQ_INT_COAL_CNT, 0x1);
+	hisi_sas_write32(hisi_hba, INT_COAL_EN, 0x3);
+	/* configure the interrupt coalescing timeout period 10us */
+	hisi_sas_write32(hisi_hba, OQ_INT_COAL_TIME, 0xa);
+	/* configure the count of CQ entries 10 */
+	hisi_sas_write32(hisi_hba, OQ_INT_COAL_CNT, 0xa);
 	hisi_sas_write32(hisi_hba, CQ_INT_CONVERGE_EN,
 			 hisi_sas_intr_conv);
 	hisi_sas_write32(hisi_hba, OQ_INT_SRC, 0xffff);
@@ -2797,14 +2799,15 @@ static void config_intr_coal_v3_hw(struct hisi_hba *hisi_hba)
 {
 	/* config those registers between enable and disable PHYs */
 	hisi_sas_stop_phys(hisi_hba);
+	hisi_sas_write32(hisi_hba, INT_COAL_EN, 0x3);
 
 	if (hisi_hba->intr_coal_ticks == 0 ||
 	    hisi_hba->intr_coal_count == 0) {
-		hisi_sas_write32(hisi_hba, INT_COAL_EN, 0x1);
-		hisi_sas_write32(hisi_hba, OQ_INT_COAL_TIME, 0x1);
-		hisi_sas_write32(hisi_hba, OQ_INT_COAL_CNT, 0x1);
+		/* configure the interrupt coalescing timeout period 10us */
+		hisi_sas_write32(hisi_hba, OQ_INT_COAL_TIME, 0xa);
+		/* configure the count of CQ entries 10 */
+		hisi_sas_write32(hisi_hba, OQ_INT_COAL_CNT, 0xa);
 	} else {
-		hisi_sas_write32(hisi_hba, INT_COAL_EN, 0x3);
 		hisi_sas_write32(hisi_hba, OQ_INT_COAL_TIME,
 				 hisi_hba->intr_coal_ticks);
 		hisi_sas_write32(hisi_hba, OQ_INT_COAL_CNT,