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Date: Thu, 28 Sep 2023 12:10:48 +0200
From: Jérôme Pouiller
<jerome.pouiller@...abs.com>
To: linux-wireless@...r.kernel.org, Kalle Valo <kvalo@...nel.org>
Cc: linux-kernel@...r.kernel.org, Felix Fietkau <nbd@....name>,
Felipe Negrelli Wolter <felipe.negrelliwolter@...abs.com>,
Olivier Souloumiac <olivier.souloumiac@...abs.com>,
Alexandr Suslenko <suslenko.o@...x.systems>,
Jérôme Pouiller
<jerome.pouiller@...abs.com>
Subject: [PATCH] wifi: wfx: fix case where rates are out of order
From: Felipe Negrelli Wolter <felipe.negrelliwolter@...abs.com>
When frames are sent over the air, the device always applies the data
rates in descending order. The driver assumed Minstrel also provided
rate in descending order.
However, in some cases, Minstrel can a choose a fallback rate greater
than the primary rate. In this case, the two rates was inverted, the
device try highest rate first and we get many retries.
Since the device always apply rates in descending order. The workaround
is to drop rate when it higher than its predecessor in the rate list.
Thus [ 4, 5, 3 ] become [ 4, 3 ].
This patch has been tested in isolated room with a series of
attenuators. Here are the Minstrel statistics with 80dBm of attenuation:
Without the fix:
best ____________rate__________ ____statistics___ _____last____ ______sum-of________
mode guard # rate [name idx airtime max_tp] [avg(tp) avg(prob)] [retry|suc|att] [#success | #attempts]
HT20 LGI 1 S MCS0 0 1477 5.6 5.2 82.7 3 0 0 3 4
HT20 LGI 1 MCS1 1 738 10.6 0.0 0.0 0 0 0 0 1
HT20 LGI 1 D MCS2 2 492 14.9 13.5 81.5 5 0 0 5 9
HT20 LGI 1 C MCS3 3 369 18.8 17.6 84.3 5 0 0 76 96
HT20 LGI 1 A P MCS4 4 246 25.4 22.4 79.5 5 0 0 11268 14026
HT20 LGI 1 B S MCS5 5 185 30.7 19.7 57.7 5 8 9 3918 9793
HT20 LGI 1 MCS6 6 164 33.0 0.0 0.0 5 0 0 6 102
HT20 LGI 1 MCS7 7 148 35.1 0.0 0.0 0 0 0 0 44
With the fix:
best ____________rate__________ ____statistics___ _____last____ ______sum-of________
mode guard # rate [name idx airtime max_tp] [avg(tp) avg(prob)] [retry|suc|att] [#success | #attempts]
HT20 LGI 1 S MCS0 0 1477 5.6 1.8 28.6 1 0 0 1 5
HT20 LGI 1 DP MCS1 1 738 10.6 9.7 82.6 4 0 0 14 34
HT20 LGI 1 MCS2 2 492 14.9 9.2 55.4 5 0 0 52 77
HT20 LGI 1 B S MCS3 3 369 18.8 15.6 74.9 5 1 1 417 554
HT20 LGI 1 A MCS4 4 246 25.4 16.7 59.2 5 1 1 13812 17951
HT20 LGI 1 C S MCS5 5 185 30.7 14.0 41.0 5 1 5 57 640
HT20 LGI 1 MCS6 6 164 33.0 0.0 0.0 0 0 1 0 48
HT20 LGI 1 S MCS7 7 148 35.1 0.0 0.0 0 0 0 0 36
We can notice the device try now to send with lower rates (and high
success rates). At the end, we measured 20-25% better throughput with
this patch.
Fixes: 9bca45f3d6924 "staging: wfx: allow to send 802.11 frames"
Tested-by: Olivier Souloumiac <olivier.souloumiac@...abs.com>
Tested-by: Alexandr Suslenko <suslenko.o@...x.systems>
Reported-by: Alexandr Suslenko <suslenko.o@...x.systems>
Co-developed-by: Jérôme Pouiller <jerome.pouiller@...abs.com>
Signed-off-by: Jérôme Pouiller <jerome.pouiller@...abs.com>
---
drivers/net/wireless/silabs/wfx/data_tx.c | 71 +++++++++--------------
1 file changed, 29 insertions(+), 42 deletions(-)
diff --git a/drivers/net/wireless/silabs/wfx/data_tx.c b/drivers/net/wireless/silabs/wfx/data_tx.c
index 6a5e52a96d183..caa22226b01bc 100644
--- a/drivers/net/wireless/silabs/wfx/data_tx.c
+++ b/drivers/net/wireless/silabs/wfx/data_tx.c
@@ -226,53 +226,40 @@ static u8 wfx_tx_get_link_id(struct wfx_vif *wvif, struct ieee80211_sta *sta,
static void wfx_tx_fixup_rates(struct ieee80211_tx_rate *rates)
{
- int i;
- bool finished;
+ bool has_rate0 = false;
+ int i, j;
- /* Firmware is not able to mix rates with different flags */
- for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
- if (rates[0].flags & IEEE80211_TX_RC_SHORT_GI)
- rates[i].flags |= IEEE80211_TX_RC_SHORT_GI;
- if (!(rates[0].flags & IEEE80211_TX_RC_SHORT_GI))
+ for (i = 1, j = 1; j < IEEE80211_TX_MAX_RATES; j++) {
+ if (rates[j].idx == -1)
+ break;
+ /* The device use the rates in descending order, whatever the request from minstrel.
+ * We have to trade off here. Most important is to respect the primary rate
+ * requested by minstrel. So, we drops the entries with rate higher than the
+ * previous.
+ */
+ if (rates[j].idx >= rates[i - 1].idx) {
+ rates[i - 1].count += rates[j].count;
+ rates[i - 1].count = min_t(u16, 15, rates[i - 1].count);
+ } else {
+ memcpy(rates + i, rates + j, sizeof(rates[i]));
+ if (rates[i].idx == 0)
+ has_rate0 = true;
+ /* The device apply Short GI only on the first rate */
rates[i].flags &= ~IEEE80211_TX_RC_SHORT_GI;
- if (!(rates[0].flags & IEEE80211_TX_RC_USE_RTS_CTS))
- rates[i].flags &= ~IEEE80211_TX_RC_USE_RTS_CTS;
- }
-
- /* Sort rates and remove duplicates */
- do {
- finished = true;
- for (i = 0; i < IEEE80211_TX_MAX_RATES - 1; i++) {
- if (rates[i + 1].idx == rates[i].idx &&
- rates[i].idx != -1) {
- rates[i].count += rates[i + 1].count;
- if (rates[i].count > 15)
- rates[i].count = 15;
- rates[i + 1].idx = -1;
- rates[i + 1].count = 0;
-
- finished = false;
- }
- if (rates[i + 1].idx > rates[i].idx) {
- swap(rates[i + 1], rates[i]);
- finished = false;
- }
+ i++;
}
- } while (!finished);
+ }
/* Ensure that MCS0 or 1Mbps is present at the end of the retry list */
- for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
- if (rates[i].idx == 0)
- break;
- if (rates[i].idx == -1) {
- rates[i].idx = 0;
- rates[i].count = 8; /* == hw->max_rate_tries */
- rates[i].flags = rates[i - 1].flags & IEEE80211_TX_RC_MCS;
- break;
- }
+ if (!has_rate0 && i < IEEE80211_TX_MAX_RATES) {
+ rates[i].idx = 0;
+ rates[i].count = 8; /* == hw->max_rate_tries */
+ rates[i].flags = rates[0].flags & IEEE80211_TX_RC_MCS;
+ i++;
+ }
+ for (; i < IEEE80211_TX_MAX_RATES; i++) {
+ memset(rates + i, 0, sizeof(rates[i]));
+ rates[i].idx = -1;
}
- /* All retries use long GI */
- for (i = 1; i < IEEE80211_TX_MAX_RATES; i++)
- rates[i].flags &= ~IEEE80211_TX_RC_SHORT_GI;
}
static u8 wfx_tx_get_retry_policy_id(struct wfx_vif *wvif, struct ieee80211_tx_info *tx_info)
--
2.39.2
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