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From:   Ping-Ke Shih <pkshih@realtek.com>
To:     Peter Kosyh <pkosyh@yandex.ru>
CC:     "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Kalle Valo <kvalo@kernel.org>,
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        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "lvc-project@linuxtesting.org" <lvc-project@linuxtesting.org>
Subject: RE: [PATCH] rtlwifi: rtl8192se: remove redundant rtl_get_bbreg call
Thread-Topic: [PATCH] rtlwifi: rtl8192se: remove redundant rtl_get_bbreg call
Thread-Index: AQHZCIlNZy/RMGZSW0e7asaR+s5GG65gGCIQ
Date:   Tue, 6 Dec 2022 02:01:58 +0000
Message-ID: <cf3d07ff543d4c009dbf51ad7a4d4b21@realtek.com>
References: <20221205085342.677329-1-pkosyh@yandex.ru>
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> -----Original Message-----
> From: Peter Kosyh <pkosyh@yandex.ru>
> Sent: Monday, December 5, 2022 4:54 PM
> To: Ping-Ke Shih <pkshih@realtek.com>
> Cc: Peter Kosyh <pkosyh@yandex.ru>; David S. Miller <davem@davemloft.net>; Eric Dumazet
> <edumazet@google.com>; Kalle Valo <kvalo@kernel.org>; Jakub Kicinski <kuba@kernel.org>; Paolo Abeni
> <pabeni@redhat.com>; linux-wireless@vger.kernel.org; netdev@vger.kernel.org;
> linux-kernel@vger.kernel.org; lvc-project@linuxtesting.org
> Subject: [PATCH] rtlwifi: rtl8192se: remove redundant rtl_get_bbreg call
> 
> Extra rtl_get_bbreg looks like redundant reading. The read has
> already been done in the "else" branch. Compile test only.

Originally, the code is 

01 if (rfpi_enable)
02     val = get_from_interface_A();
03 else
04    val = get_from_interface_B();
05
06 val = get_from_interface_B();

This patch is to remove line 06, and it looks like logic is changed. However,
'rfpi_enable' is decided by 0x820[8] and 0x828[8] set by rtl8192sephy_reg_2t2rarray[]
table, and 'rfpi_enable' is always false. I think this is why nobody can't
encounter problem and find this bug.

> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Signed-off-by: Peter Kosyh <pkosyh@yandex.ru>

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

> ---
> If this code is important for the operation of the hardware, then it would
> be nice to comment on it.
> 
>  drivers/net/wireless/realtek/rtlwifi/rtl8192se/phy.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/drivers/net/wireless/realtek/rtlwifi/rtl8192se/phy.c
> b/drivers/net/wireless/realtek/rtlwifi/rtl8192se/phy.c
> index aaa004d4d6d0..09591a0b5a81 100644
> --- a/drivers/net/wireless/realtek/rtlwifi/rtl8192se/phy.c
> +++ b/drivers/net/wireless/realtek/rtlwifi/rtl8192se/phy.c
> @@ -115,9 +115,6 @@ static u32 _rtl92s_phy_rf_serial_read(struct ieee80211_hw *hw,
>  		retvalue = rtl_get_bbreg(hw, pphyreg->rf_rb,
>  					 BLSSI_READBACK_DATA);
> 
> -	retvalue = rtl_get_bbreg(hw, pphyreg->rf_rb,
> -				 BLSSI_READBACK_DATA);
> -
>  	rtl_dbg(rtlpriv, COMP_RF, DBG_TRACE, "RFR-%d Addr[0x%x]=0x%x\n",
>  		rfpath, pphyreg->rf_rb, retvalue);
> 
> --
> 2.38.1