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Date:   Wed, 20 Apr 2022 07:20:48 +0200
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To:     Bo Jiao <bo.jiao@mediatek.com>
Cc:     linux-wireless <linux-wireless@vger.kernel.org>,
        Ryder Lee <ryder.lee@mediatek.com>,
        Sujuan Chen <sujuan.chen@mediatek.com>,
        Shayne Chen <shayne.chen@mediatek.com>,
        Evelyn Tsai <evelyn.tsai@mediatek.com>,
        linux-mediatek <linux-mediatek@lists.infradead.org>
References: <20220420040346.8378-1-bo.jiao@mediatek.com>
From:   Felix Fietkau <nbd@nbd.name>
Subject: Re: [PATCH] mt76: mt7915: report qos_ctl without ACK policy
In-Reply-To: <20220420040346.8378-1-bo.jiao@mediatek.com>
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On 20.04.22 06:03, Bo Jiao wrote:
> From: Bo Jiao <Bo.Jiao@mediatek.com>
> 
> there is no need to report to the mac80211 layer the ACK policy which may
> cause rx out-of-order issue, because the hardware rmac module already handle it
> 
> Signed-off-by: Bo Jiao <Bo.Jiao@mediatek.com>
> ---
>   drivers/net/wireless/mediatek/mt76/mt7915/mac.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/net/wireless/mediatek/mt76/mt7915/mac.c b/drivers/net/wireless/mediatek/mt76/mt7915/mac.c
> index b47aea6..5080280 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt7915/mac.c
> +++ b/drivers/net/wireless/mediatek/mt76/mt7915/mac.c
> @@ -675,6 +675,11 @@ mt7915_mac_fill_rx(struct mt7915_dev *dev, struct sk_buff *skb)
>   
>   		fc = cpu_to_le16(FIELD_GET(MT_RXD6_FRAME_CONTROL, v0));
>   		qos_ctl = FIELD_GET(MT_RXD8_QOS_CTL, v2);
> +		/*
> +		 * there is no need to report the ACK policy to the
> +		 * mac80211 layer, because hw has already processed it.
> +		 */
> +		qos_ctl &= ~IEEE80211_QOS_CTL_ACK_POLICY_MASK;
I don't understand this change at all. First of all, the qos_ctl field 
isn't really reported to the mac80211 layer, it's used in mt76 internally.
The rx reorder code uses it to detect no-ack policy in order to avoid 
reordering for it.
Since you're masking out the ack policy, the value will be 
IEEE80211_QOS_CTL_ACK_POLICY_NORMAL, which ends up forcibly enabling rx 
reordering, even when the policy indicates no-ack.
How does this help, and what part does the rmac module already handle?

- Felix