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From:   Ping-Ke Shih <pkshih@realtek.com>
To:     Sascha Hauer <s.hauer@pengutronix.de>,
        linux-wireless <linux-wireless@vger.kernel.org>
CC:     Hans Ulli Kroll <linux@ulli-kroll.de>,
        Larry Finger <Larry.Finger@lwfinger.net>,
        Tim K <tpkuester@gmail.com>, "Alex G ." <mr.nuke.me@gmail.com>,
        Nick Morrow <morrownr@gmail.com>,
        Viktor Petrenko <g0000ga@gmail.com>,
        Andreas Henriksson <andreas@fatal.se>,
        ValdikSS <iam@valdikss.org.ru>,
        "kernel@pengutronix.de" <kernel@pengutronix.de>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: RE: [PATCH v3 2/4] wifi: rtw88: rtw8821c: Fix rfe_option field width
Thread-Topic: [PATCH v3 2/4] wifi: rtw88: rtw8821c: Fix rfe_option field width
Thread-Index: AQHZcTWezKEckbP2+EWGT9gRs25X0K8wOBOw
Date:   Tue, 18 Apr 2023 00:32:41 +0000
Message-ID: <6df1e0238b5a49bdbed274fffe4e6ce3@realtek.com>
References: <20230417140358.2240429-1-s.hauer@pengutronix.de>
 <20230417140358.2240429-3-s.hauer@pengutronix.de>
In-Reply-To: <20230417140358.2240429-3-s.hauer@pengutronix.de>
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> -----Original Message-----
> From: Sascha Hauer <s.hauer@pengutronix.de>
> Sent: Monday, April 17, 2023 10:04 PM
> To: linux-wireless <linux-wireless@vger.kernel.org>
> Cc: Hans Ulli Kroll <linux@ulli-kroll.de>; Larry Finger <Larry.Finger@lwfinger.net>; Ping-Ke Shih
> <pkshih@realtek.com>; Tim K <tpkuester@gmail.com>; Alex G . <mr.nuke.me@gmail.com>; Nick Morrow
> <morrownr@gmail.com>; Viktor Petrenko <g0000ga@gmail.com>; Andreas Henriksson <andreas@fatal.se>;
> ValdikSS <iam@valdikss.org.ru>; kernel@pengutronix.de; Sascha Hauer <s.hauer@pengutronix.de>;
> stable@vger.kernel.org
> 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@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

Reviewed-by: Ping-Ke Shih <pkshih@realtek.com>

> ---
>  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