wifi: rtw88: Move register access from rtw_bf_assoc() outside the RCU

USB and (upcoming) SDIO support may sleep in the read/write handlers.
Shrink the RCU critical section so it only cover the call to
ieee80211_find_sta() and finding the ic_vht_cap/vht_cap based on the
found station. This moves the chip's BFEE configuration outside the
rcu_read_lock section and thus prevent "scheduling while atomic" or
"Voluntary context switch within RCU read-side critical section!"
warnings when accessing the registers using an SDIO card (which is
where this issue has been spotted in the real world - but it also
affects USB cards).

Reviewed-by: Ping-Ke Shih <pkshih@realtek.com>
Tested-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230108211324.442823-2-martin.blumenstingl@googlemail.com

diff --git a/drivers/net/wireless/realtek/rtw88/bf.c b/drivers/net/wireless/realtek/rtw88/bf.c
index 038a30b..c827c4a 100644 (file)
--- a/drivers/net/wireless/realtek/rtw88/bf.c
+++ b/drivers/net/wireless/realtek/rtw88/bf.c
@@ -49,19 +49,23 @@ void rtw_bf_assoc(struct rtw_dev *rtwdev, struct ieee80211_vif *vif,
 
        sta = ieee80211_find_sta(vif, bssid);
        if (!sta) {
+               rcu_read_unlock();
+
                rtw_warn(rtwdev, "failed to find station entry for bss %pM\n",
                         bssid);
-               goto out_unlock;
+               return;
        }
 
        ic_vht_cap = &hw->wiphy->bands[NL80211_BAND_5GHZ]->vht_cap;
        vht_cap = &sta->deflink.vht_cap;
 
+       rcu_read_unlock();
+
        if ((ic_vht_cap->cap & IEEE80211_VHT_CAP_MU_BEAMFORMEE_CAPABLE) &&
            (vht_cap->cap & IEEE80211_VHT_CAP_MU_BEAMFORMER_CAPABLE)) {
                if (bfinfo->bfer_mu_cnt >= chip->bfer_mu_max_num) {
                        rtw_dbg(rtwdev, RTW_DBG_BF, "mu bfer number over limit\n");
-                       goto out_unlock;
+                       return;
                }
 
                ether_addr_copy(bfee->mac_addr, bssid);
@@ -75,7 +79,7 @@ void rtw_bf_assoc(struct rtw_dev *rtwdev, struct ieee80211_vif *vif,
                   (vht_cap->cap & IEEE80211_VHT_CAP_SU_BEAMFORMER_CAPABLE)) {
                if (bfinfo->bfer_su_cnt >= chip->bfer_su_max_num) {
                        rtw_dbg(rtwdev, RTW_DBG_BF, "su bfer number over limit\n");
-                       goto out_unlock;
+                       return;
                }
 
                sound_dim = vht_cap->cap &
@@ -98,9 +102,6 @@ void rtw_bf_assoc(struct rtw_dev *rtwdev, struct ieee80211_vif *vif,
 
                rtw_chip_config_bfee(rtwdev, rtwvif, bfee, true);
        }
-
-out_unlock:
-       rcu_read_unlock();
 }
 
 void rtw_bf_init_bfer_entry_mu(struct rtw_dev *rtwdev,