> -----Original Message-----
> From: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
> Sent: Monday, April 17, 2023 10:04 PM
> To: linux-wireless <linux-wireless@xxxxxxxxxxxxxxx>
> Cc: Hans Ulli Kroll <linux@xxxxxxxxxxxxx>; Larry Finger <Larry.Finger@xxxxxxxxxxxx>; Ping-Ke Shih
> <pkshih@xxxxxxxxxxx>; Tim K <tpkuester@xxxxxxxxx>; Alex G . <mr.nuke.me@xxxxxxxxx>; Nick Morrow
> <morrownr@xxxxxxxxx>; Viktor Petrenko <g0000ga@xxxxxxxxx>; Andreas Henriksson <andreas@xxxxxxxx>;
> ValdikSS <iam@xxxxxxxxxxxxxxx>; kernel@xxxxxxxxxxxxxx; Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>;
> stable@xxxxxxxxxxxxxxx
> Subject: [PATCH v3 2/4] wifi: rtw88: rtw8821c: Fix rfe_option field width
>
> 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@xxxxxxxxxxxxxx>
> Tested-by: Alexandru gagniuc <mr.nuke.me@xxxxxxxxx>
> Tested-by: Larry Finger <Larry.Finger@xxxxxxxxxxxx>
> Tested-by: ValdikSS <iam@xxxxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
Reviewed-by: Ping-Ke Shih <pkshih@xxxxxxxxxxx>
> ---
> 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
