RE: [PATCH v2 2/2] wifi: rtl8xxxu: Use a longer retry limit of 48

[Ping-Ke Shih <pkshih@realtek.com>]

> -----Original Message-----
> From: Bitterblue Smith <rtl8821cerfe2@gmail.com>
> Sent: Sunday, January 8, 2023 11:08 PM
> To: linux-wireless@vger.kernel.org
> Cc: Jes Sorensen <Jes.Sorensen@gmail.com>; Ping-Ke Shih <pkshih@realtek.com>
> Subject: [PATCH v2 2/2] wifi: rtl8xxxu: Use a longer retry limit of 48
> 
> The Realtek rate control algorithm goes back and forth a lot between
> the highest and the lowest rate it's allowed to use. This is due to
> a lot of frames being dropped because the retry limits set by
> IEEE80211_CONF_CHANGE_RETRY_LIMITS are too low. (Experimentally, they
> are 4 for long frames and 7 for short frames.)
> 
> The vendor drivers hardcode the value 48 for both retry limits (for
> station mode), which makes dropped frames very rare and thus the rate
> control is more stable.
> 
> Because most Realtek chips handle the rate control in the firmware,
> which can't be modified, ignore the limits set by
> IEEE80211_CONF_CHANGE_RETRY_LIMITS and use the value 48 (set during
> chip initialisation), same as the vendor drivers.
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>

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

> ---
> v2:
>  - Use Cc tag instead of Fixes.
> ---
>  drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c | 9 ---------
>  1 file changed, 9 deletions(-)
> 
> diff --git a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
> b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
> index 4c76fad67150..ab4074caf191 100644
> --- a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
> +++ b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
> @@ -6184,7 +6184,6 @@ static int rtl8xxxu_config(struct ieee80211_hw *hw, u32 changed)
>  {
>  	struct rtl8xxxu_priv *priv = hw->priv;
>  	struct device *dev = &priv->udev->dev;
> -	u16 val16;
>  	int ret = 0, channel;
>  	bool ht40;
> 
> @@ -6194,14 +6193,6 @@ static int rtl8xxxu_config(struct ieee80211_hw *hw, u32 changed)
>  			 __func__, hw->conf.chandef.chan->hw_value,
>  			 changed, hw->conf.chandef.width);
> 
> -	if (changed & IEEE80211_CONF_CHANGE_RETRY_LIMITS) {
> -		val16 = ((hw->conf.long_frame_max_tx_count <<
> -			  RETRY_LIMIT_LONG_SHIFT) & RETRY_LIMIT_LONG_MASK) |
> -			((hw->conf.short_frame_max_tx_count <<
> -			  RETRY_LIMIT_SHORT_SHIFT) & RETRY_LIMIT_SHORT_MASK);
> -		rtl8xxxu_write16(priv, REG_RETRY_LIMIT, val16);
> -	}
> -
>  	if (changed & IEEE80211_CONF_CHANGE_CHANNEL) {
>  		switch (hw->conf.chandef.width) {
>  		case NL80211_CHAN_WIDTH_20_NOHT:
> --
> 2.38.0
> 
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