[PATCH v3 2/4] wifi: rtw88: rtw8821c: Fix rfe_option field width

[Sascha Hauer <s.hauer@pengutronix.de>]

On my RTW8821CU chipset rfe_option reads as 0x22. Looking at the
vendor driver suggests that the field width of rfe_option is 5 bit,
so rfe_option should be masked with 0x1f.

Without this the rfe_option comparisons with 2 further down the
driver evaluate as false when they should really evaluate as true.
The effect is that 2G channels do not work.

rfe_option is also used as an array index into rtw8821c_rfe_defs[].
rtw8821c_rfe_defs[34] (0x22) was added as part of adding USB support,
likely because rfe_option reads as 0x22. As this now becomes 0x2,
rtw8821c_rfe_defs[34] is no longer used and can be removed.

Note that this might not be the whole truth. In the vendor driver
there are indeed places where the unmasked rfe_option value is used.
However, the driver has several places where rfe_option is tested
with the pattern if (rfe_option == 2 || rfe_option == 0x22) or
if (rfe_option == 4 || rfe_option == 0x24), so that rfe_option BIT(5)
has no influence on the code path taken. We therefore mask BIT(5)
out from rfe_option entirely until this assumption is proved wrong
by some chip variant we do not know yet.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Tested-by: Alexandru gagniuc <mr.nuke.me@gmail.com>
Tested-by: Larry Finger <Larry.Finger@lwfinger.net>
Tested-by: ValdikSS <iam@valdikss.org.ru>
Cc: stable@vger.kernel.org
---
 drivers/net/wireless/realtek/rtw88/rtw8821c.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/wireless/realtek/rtw88/rtw8821c.c b/drivers/net/wireless/realtek/rtw88/rtw8821c.c
index 17f800f6efbd0..67efa58dd78ee 100644
--- a/drivers/net/wireless/realtek/rtw88/rtw8821c.c
+++ b/drivers/net/wireless/realtek/rtw88/rtw8821c.c
@@ -47,7 +47,7 @@ static int rtw8821c_read_efuse(struct rtw_dev *rtwdev, u8 *log_map)
 
 	map = (struct rtw8821c_efuse *)log_map;
 
-	efuse->rfe_option = map->rfe_option;
+	efuse->rfe_option = map->rfe_option & 0x1f;
 	efuse->rf_board_option = map->rf_board_option;
 	efuse->crystal_cap = map->xtal_k;
 	efuse->pa_type_2g = map->pa_type;
@@ -1537,7 +1537,6 @@ static const struct rtw_rfe_def rtw8821c_rfe_defs[] = {
 	[2] = RTW_DEF_RFE_EXT(8821c, 0, 0, 2),
 	[4] = RTW_DEF_RFE_EXT(8821c, 0, 0, 2),
 	[6] = RTW_DEF_RFE(8821c, 0, 0),
-	[34] = RTW_DEF_RFE(8821c, 0, 0),
 };
 
 static struct rtw_hw_reg rtw8821c_dig[] = {
-- 
2.39.2