[PATCH ath-next] wifi: ath12k: Reduce RX SRNG interrupt timer threshold to 200us

[Thiraviyam Mariyappan]

Currently when RX traffic is low or intermittent, the RX SRNG interrupt
mitigation logic defers packet processing for up to 500us via
HAL_SRNG_INT_TIMER_THRESHOLD_RX.

This causes excessive RX servicing delay, leading to increased end-to-end
latency and degraded TCP performance in low-concurrency scenarios.

In single-client single-stream TCP tests using 5G EHT160 (NSS 2x2) mode,
throughput drops to ~400 Mbps DL and UL instead of the expected ~600 Mbps.

In addition, UDP UL end-to-end latency measured in 5G VHT80 (NSS 4x4) mode
increases by up to ~48% (~570us versus ~270us) across frame sizes from
76 to 1518 bytes in uplink and bidirectional traffic, indicating delayed
RX servicing under sparse traffic conditions.

To address this issue, reduce the RX SRNG interrupt timer threshold from
500us to 200us so that received packets are serviced more promptly under
low-rate and intermittent RX traffic.

With this change, single-client single-stream TCP throughput in EHT160 is
restored to expected levels ~600 Mbps TCP DL/UL and UDP UL end-to-end
latency in VHT80 returns to baseline values ~270us across all tested frame
sizes. Under high RX load, no throughput regression is observed, as RX
rings are already serviced frequently. The primary implication is a modest
increase in RX interrupt frequency under low traffic, with no observed
functional, stability, or performance regressions on tested platforms.

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.6-01181-QCAHKSWPL_SILICONZ-1

Signed-off-by: Thiraviyam Mariyappan <thiraviyam.mariyappan at oss.qualcomm.com>
---
 drivers/net/wireless/ath/ath12k/hal.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/ath/ath12k/hal.h b/drivers/net/wireless/ath/ath12k/hal.h
index 21c551d8b248..2a5bdf6d7653 100644
--- a/drivers/net/wireless/ath/ath12k/hal.h
+++ b/drivers/net/wireless/ath/ath12k/hal.h
@@ -1024,7 +1024,7 @@ enum hal_wbm_rel_desc_type {
 
 /* Interrupt mitigation - timer threshold in us */
 #define HAL_SRNG_INT_TIMER_THRESHOLD_TX 1000
-#define HAL_SRNG_INT_TIMER_THRESHOLD_RX 500
+#define HAL_SRNG_INT_TIMER_THRESHOLD_RX 200
 #define HAL_SRNG_INT_TIMER_THRESHOLD_OTHER 256
 
 enum hal_srng_mac_type {

base-commit: 972c4dd19cb92e03d75b66c426cfade07582a1ba
-- 
2.34.1