wifi: ath12k: change MAC buffer ring size to 2048

For WCN7850, there is a SRNG named MAC buffer ring, i.e.,
dp->rx_mac_buf_ring. During initialization, it is setup
by host and then under control of firmware. During RX
process, firmware fetches buffers from
dp->rx_refill_buf_ring to fill that MAC buffer ring,
and those buffers are taken by RXDMA to carry real WLAN
frames received from air.

Currently a low RX throughput is observed. Checking
firmware log, lots of errors are reported by MAC buffer
ring, complaining that it is running out of buffers,
which further indicates that RXDMA is suffering from
starvation. Currently the size of dp->rx_mac_buf_ring
is configured as 1024. After changing it to 2048, those
error messages are reduced, and a 6.4% increase is seen
in peak throughput. Note that 2048 is an empirical
value. It is chosen here because the RX throughput
meets our expectation after the change.

This change only applies to WCN7850 since other
chips don't have a MAC buffer ring.

Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.0-03427-QCAHMTSWPL_V1.0_V2.0_SILICONZ-1.15378.4

Signed-off-by: Baochen Qiang <quic_bqiang@quicinc.com>
Acked-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://msgid.link/20231129020414.56425-4-quic_bqiang@quicinc.com

drivers/net/wireless/ath/ath12k/dp.h

@@ -170,6 +170,7 @@ struct ath12k_pdev_dp {
 #define DP_REO_CMD_RING_SIZE		128
 #define DP_REO_STATUS_RING_SIZE		2048
 #define DP_RXDMA_BUF_RING_SIZE		4096
+#define DP_RX_MAC_BUF_RING_SIZE		2048
 #define DP_RXDMA_REFILL_RING_SIZE	2048
 #define DP_RXDMA_ERR_DST_RING_SIZE	1024
 #define DP_RXDMA_MON_STATUS_RING_SIZE	1024

drivers/net/wireless/ath/ath12k/dp_rx.c

@@ -4086,7 +4086,7 @@ int ath12k_dp_rx_alloc(struct ath12k_base *ab)
 			ret = ath12k_dp_srng_setup(ab,
 						   &dp->rx_mac_buf_ring[i],
 						   HAL_RXDMA_BUF, 1,
-						   i, 1024);
+						   i, DP_RX_MAC_BUF_RING_SIZE);
 			if (ret) {
 				ath12k_warn(ab, "failed to setup rx_mac_buf_ring %d\n",
 					    i);