> -----Original Message-----
> From: Bitterblue Smith <rtl8821cerfe2@xxxxxxxxx>
> Sent: Saturday, December 31, 2022 12:54 AM
> To: linux-wireless@xxxxxxxxxxxxxxx
> Cc: Jes Sorensen <Jes.Sorensen@xxxxxxxxx>; Ping-Ke Shih <pkshih@xxxxxxxxxxx>
> Subject: [PATCH 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.
I have similar feeling with Realtek 802.11ac chips as well, but I didn't
dig further years ago. Maybe, it could have TX EVM problem.
>
> 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.
>
> Fixes: 26f1fad29ad9 ("New driver: rtl8xxxu (mac80211)")
No sure if "Fixes" is suitable to this patch, because original looks well but
bad performance in real.
> Signed-off-by: Bitterblue Smith <rtl8821cerfe2@xxxxxxxxx>
Reviewed-by: Ping-Ke Shih <pkshih@xxxxxxxxxxx>
> ---
> 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 f5fd3c448587..9bca5e837583 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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