We identified an issue where the RSSI values for beacons from
legacy rates AP are incorrect, consistently showing -128.
This issue was identified on the Intel AX210 WiFi chip with
firmware version "89.202a2f7b.0 ty-a0-gf-a0-89.ucode op_mode iwlmvm"
To reproduce this issue :
- Setup an AP with legacy rates on the frequency 2422Mhz
- And on the device with Intel AX210 chip run:
iw phy0 interface add mon0 type monitor
ip link set mon0 up
iw dev mon0 set freq 2422
tcpdump -i mon0 -v
After debugging, we discovered that the RSSI values become
correct when a printk() statement is added to the RX path
in the iwlwifi driver, as shown the patch below.
Alternatively, adding udelay() instead of printk() also corrects
the incorrect RSSI values; however, this approach leads to
firmware warnings and errors:
````
--- a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
+++ b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
@@ -1543,7 +1543,7 @@ restart:
}
IWL_DEBUG_RX(trans, "Q %d: HW = %d, SW = %d\n", rxq->id, r, i);
-
+ udelay(500);
rxb = iwl_pcie_get_rxb(trans, rxq, i, &join);
if (!rxb)
goto out;
````
Additionally, we found that deleting all existing interfaces on
the PHY and then creating a monitor interface resolves this issue:
iw dev wlan0 interface del # In case we have wlan0 as the existing interface.
iw phy0 interface add mon0 type monitor
ip link set mon0 up
iw dev mon0 set freq 2422
However, in this case, it will not be possible to execute the scan
command with the monitor interface to prompt the firmware to
trigger the country code.
Has anyone encountered this issue before or have any insights
into the potential root cause ?
Signed-off-by: Issam Hamdi <ih@xxxxxxxxxxxxxxxxxx>
---
drivers/net/wireless/intel/iwlwifi/pcie/rx.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
index afb88eab8174..b0ce71e6260b 100644
--- a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
+++ b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
@@ -1544,6 +1544,8 @@ static int iwl_pcie_rx_handle(struct iwl_trans *trans, int queue, int budget)
IWL_DEBUG_RX(trans, "Q %d: HW = %d, SW = %d\n", rxq->id, r, i);
+ printk(KERN_DEBUG "Got new packet\n");
+
rxb = iwl_pcie_get_rxb(trans, rxq, i, &join);
if (!rxb)
goto out;
base-commit: 2b94751626a6d49bbe42a19cc1503bd391016bd5
--
2.39.2
