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[SRU,N/M,2/2] wifi: rtw89: pci: correct TX resource checking for PCI DMA channel of firmware command

Message ID 20240524054606.48426-3-hui.wang@canonical.com
State New
Headers show
Series Fix the RTL8852CE BT FW Crash based on SER false alarm | expand

Commit Message

Hui Wang May 24, 2024, 5:46 a.m. UTC 
From: Ping-Ke Shih <pkshih@realtek.com>

BugLink: https://bugs.launchpad.net/bugs/2060904

The DMA channel of firmware command doesn't use TX WD (WiFi descriptor), so
don't need to consider number of TX WD as factor of TX resource. Otherwise,
during pause state (a transient state to switch to/from low power mode)
firmware commands could be dropped and driver throws warnings suddenly:

   rtw89_8852ce 0000:04:00.0: no tx fwcmd resource
   rtw89_8852ce 0000:04:00.0: failed to send h2c

The case we met is that driver sends RSSI strength of firmware command at
RX path that could be running concurrently with switching low power mode.
The missing of this firmware command doesn't affect user experiences,
because the RSSI strength will be updated again after a while.

The DMA descriptors of normal packets has three layers like:

  +-------+
  | TX BD | (*n elements)
  +-------+
      |
      |   +-------+
      +-> | TX WD | (*m elements)
          +-------+
              |
              |   +--------+
              +-> |   SKB  |
                  +--------+

And, firmware command queue (TXCH 12) is a special queue that has only
two layers:

  +-------+
  | TX BD | (*n elements)
  +-------+
      |
      |   +------------------+
      +-> | firmware command |
          +------------------+

Fixes: 4a29213cd775 ("wifi: rtw89: pci: correct TX resource checking in low power mode")
Cc: stable@vger.kernel.org
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://msgid.link/20240410011316.9906-1-pkshih@realtek.com
(cherry picked from commit c6330b129786e267b14129335a08fa7c331c308d)
Signed-off-by: Hui Wang <hui.wang@canonical.com>
---
 drivers/net/wireless/realtek/rtw89/pci.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/drivers/net/wireless/realtek/rtw89/pci.c b/drivers/net/wireless/realtek/rtw89/pci.c
index 769f1ce62ebc..4ffd628aaf37 100644
--- a/drivers/net/wireless/realtek/rtw89/pci.c
+++ b/drivers/net/wireless/realtek/rtw89/pci.c
@@ -1043,7 +1043,8 @@  u32 __rtw89_pci_check_and_reclaim_tx_resource_noio(struct rtw89_dev *rtwdev,
 
 	spin_lock_bh(&rtwpci->trx_lock);
 	cnt = rtw89_pci_get_avail_txbd_num(tx_ring);
-	cnt = min(cnt, wd_ring->curr_num);
+	if (txch != RTW89_TXCH_CH12)
+		cnt = min(cnt, wd_ring->curr_num);
 	spin_unlock_bh(&rtwpci->trx_lock);
 
 	return cnt;