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Date:   Fri, 21 Oct 2022 21:32:15 +0300
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Subject: Re: [PATCH 1/5] wifi: rtl8xxxu: Add central frequency offset tracking
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To:     Ping-Ke Shih <pkshih@realtek.com>,
        "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>
Cc:     Jes Sorensen <Jes.Sorensen@gmail.com>
References: <2b29b6d9-c17e-76d6-c32f-630f24b407b7@gmail.com>
 <6a91fd1b8d5e4bf3910366121ed92f3b@realtek.com>
From:   Bitterblue Smith <rtl8821cerfe2@gmail.com>
In-Reply-To: <6a91fd1b8d5e4bf3910366121ed92f3b@realtek.com>
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On 21/10/2022 08:47, Ping-Ke Shih wrote:
> 
> 
>> -----Original Message-----
>> From: Bitterblue Smith <rtl8821cerfe2@gmail.com>
>> Sent: Monday, October 17, 2022 1:27 AM
[...]
>> +
>> +	val32 &= ~0x007ff800;
>> +	val32 |= (crystal_cap | (crystal_cap << 6)) << 11;
>> +	rtl8xxxu_write32(priv, REG_AFE_XTAL_CTRL, val32);
> 
> This could be clear:
> 
> #define XTAL1 GENMASK(22, 17)
> #define XTAL0 GENMASK(16, 11)
> 
> val32 &= ~(XTAL1 | XTAL2)
> val32 |= FIELD_PREP(XTAL1, crystal_cap) |
>          FIELD_PREP(XTAL0, crystal_cap);
> 

Ah, so that's what FIELD_PREP does.

>> +			if (priv->cfo_tracking.packet_count == 0xffffffff)
>> +				priv->cfo_tracking.packet_count = 0;
>> +			else
>> +				priv->cfo_tracking.packet_count++;
> 
> 'packet_count' is u32, so 0xffffffff + 1 will become 0. Then, just
> 
>    priv->cfo_tracking.packet_count++;
> 

I thought so, but I'm not *that* familiar with the C standard,
so I left it how I found it in one of the Realtek drivers.

>> +
>> +	if (crystal_cap > 0x3f)
>> +		crystal_cap = 0x3f;
>> +	else if (crystal_cap < 0)
>> +		crystal_cap = 0;
> 
> crystal_cap = clamp(crystal_cap, 0, 0x3f);
> 

Right, that's better.

Thanks for the reviews. I'll implement your suggestions.