wifi: rtw88: fix DTIM period handling when conf->dtim_period is zero

[ Upstream commit 9f68fdc ]

The function rtw_set_dtim_period() accepted an 'int' dtim_period parameter,
while mac80211 provides dtim_period as 'u8' in struct ieee80211_bss_conf.
In IBSS (ad-hoc) mode mac80211 may set dtim_period to 0.

The driver unconditionally wrote (dtim_period - 1) to
REG_DTIM_COUNTER_ROOT, which resulted in 0xFF when dtim_period was 0. This
caused delays in broadcast/multicast traffic processing and issues with
ad-hoc operation.

Convert the function parameter to u8 to match ieee80211_bss_conf and avoid
the underflow by writing 0 when dtim_period is 0.

Link: lwfinger/rtw88#406
Signed-off-by: Roman Peshkichev <roman.peshkichev@gmail.com>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20251125180937.22977-1-roman.peshkichev@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: Keylost

drivers/net/wireless/realtek/rtw88/main.c

@@ -684,10 +684,10 @@ void rtw_set_rx_freq_band(struct rtw_rx_pkt_stat *pkt_stat, u8 channel)
 }
 EXPORT_SYMBOL(rtw_set_rx_freq_band);
 
-void rtw_set_dtim_period(struct rtw_dev *rtwdev, int dtim_period)
+void rtw_set_dtim_period(struct rtw_dev *rtwdev, u8 dtim_period)
 {
 	rtw_write32_set(rtwdev, REG_TCR, BIT_TCR_UPDATE_TIMIE);
-	rtw_write8(rtwdev, REG_DTIM_COUNTER_ROOT, dtim_period - 1);
+	rtw_write8(rtwdev, REG_DTIM_COUNTER_ROOT, dtim_period ? dtim_period - 1 : 0);
 }
 
 void rtw_update_channel(struct rtw_dev *rtwdev, u8 center_channel,

drivers/net/wireless/realtek/rtw88/main.h

@@ -2150,7 +2150,7 @@ enum nl80211_band rtw_hw_to_nl80211_band(enum rtw_supported_band hw_band)
 }
 
 void rtw_set_rx_freq_band(struct rtw_rx_pkt_stat *pkt_stat, u8 channel);
-void rtw_set_dtim_period(struct rtw_dev *rtwdev, int dtim_period);
+void rtw_set_dtim_period(struct rtw_dev *rtwdev, u8 dtim_period);
 void rtw_get_channel_params(struct cfg80211_chan_def *chandef,
 			    struct rtw_channel_params *ch_param);
 bool check_hw_ready(struct rtw_dev *rtwdev, u32 addr, u32 mask, u32 target);