From 9a2a0862d973c9eab6a1f3efa0d4d18dcedbaf1a Mon Sep 17 00:00:00 2001
From: Wright Feng <wright.feng@cypress.com>
Date: Thu, 13 Aug 2020 02:00:16 -0500
Subject: [PATCH] brcmfmac: reserve tx credit only when txctl is ready to send
Git-commit: 9a2a0862d973c9eab6a1f3efa0d4d18dcedbaf1a
Patch-mainline: v5.9 or v5.9-rc7 (next release)
References: jsc#SLE-13430

The 4329 throughput drops from 40.2 Mbits/sec to 190 Kbits/sec in 2G
11n mode because the commit b41c232d33666 ("brcmfmac: reserve 2 credits
for host tx control path"). To fix the issue, host driver only reserves
tx control credit when there is a txctl frame is pending to send. And
we also check available credit by using "not equal to 0" instead of
"greater than 0" because tx_max and tx_seq are circled positive numbers.

Reported-by: Dmitry Osipenko <digetx@gmail.com>
Fixes: b41c232d33666 ("brcmfmac: reserve 2 credits for host tx control path")
Signed-off-by: Wright Feng <wright.feng@cypress.com>
Tested-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200813070017.89023-1-wright.feng@cypress.com
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c
@@ -683,8 +683,15 @@ static bool data_ok(struct brcmf_sdio *b
 /* To check if there's window offered */
 static bool txctl_ok(struct brcmf_sdio *bus)
 {
-	return (bus->tx_max - bus->tx_seq) != 0 &&
-	       ((bus->tx_max - bus->tx_seq) & 0x80) == 0;
+	u8 tx_rsv = 0;
+
+	/* Reserve TXCTL_CREDITS credits for txctl when it is ready to send */
+	if (bus->ctrl_frame_stat)
+		tx_rsv = TXCTL_CREDITS;
+
+	return (bus->tx_max - bus->tx_seq - tx_rsv) != 0 &&
+	       ((bus->tx_max - bus->tx_seq - tx_rsv) & 0x80) == 0;
+
 }
 
 static int