[RFC/RFT,2/4] mac80211: Add API function to set the last TX bitrate for a station

Commit Message

Toke Høiland-Jørgensen Sept. 19, 2019, 12:22 p.m. UTC

From: Toke Høiland-Jørgensen <[e-mail]>

To implement airtime queue limits, we need an estimate of the transmission
rate a station is currently transmitting at. The ath10k driver already
keeps this internally, so add an API function to pass this up to mac80211.

We also keep a pre-calculated 64-bit reciprocal that will be used in the
actual calculations, to avoid a division operation in the fast path.

Signed-off-by: Toke Høiland-Jørgensen <[e-mail]>
---
 include/net/mac80211.h     |   10 ++++++++++
 net/mac80211/ieee80211_i.h |    4 ++++
 net/mac80211/sta_info.c    |    9 +++++++++
 net/mac80211/sta_info.h    |    2 ++
 4 files changed, 25 insertions(+)

Comments

Johannes Berg Oct. 1, 2019, 8:46 a.m. UTC | #1

On Thu, 2019-09-19 at 14:22 +0200, Toke Høiland-Jørgensen wrote:

Given a ULL constant:

> +/* constants for calculating reciprocals to avoid division in fast path */
> +#define IEEE80211_RECIPROCAL_DIVISOR 0x100000000ULL

[...]

> +void ieee80211_sta_set_last_tx_bitrate(struct ieee80211_sta *pubsta,
> +				       u32 rate)
> +{
> +	struct sta_info *sta = container_of(pubsta, struct sta_info, sta);
> +
> +	sta->last_tx_bitrate = rate;
> +	sta->last_tx_bitrate_reciprocal = ((u64)IEEE80211_RECIPROCAL_DIVISOR / rate);

that cast seems unnecessary?

johannes

Toke Høiland-Jørgensen Oct. 1, 2019, 9:09 a.m. UTC | #2

Johannes Berg <[e-mail]> writes:

> On Thu, 2019-09-19 at 14:22 +0200, Toke Høiland-Jørgensen wrote:
>
> Given a ULL constant:
>
>> +/* constants for calculating reciprocals to avoid division in fast path */
>> +#define IEEE80211_RECIPROCAL_DIVISOR 0x100000000ULL
>
> [...]
>
>> +void ieee80211_sta_set_last_tx_bitrate(struct ieee80211_sta *pubsta,
>> +				       u32 rate)
>> +{
>> +	struct sta_info *sta = container_of(pubsta, struct sta_info, sta);
>> +
>> +	sta->last_tx_bitrate = rate;
>> +	sta->last_tx_bitrate_reciprocal = ((u64)IEEE80211_RECIPROCAL_DIVISOR / rate);
>
> that cast seems unnecessary?

Yeah. I only remembered to make it a ULL constant later, and forgot to
remove the cast. But I guess this should be using do_div() anyway...

-Toke

Patch

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index b12d378621b0..1b7f4a370122 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -4529,6 +4529,16 @@  void ieee80211_get_tx_rates(struct ieee80211_vif *vif,
 void ieee80211_sta_set_expected_throughput(struct ieee80211_sta *pubsta,
 					   u32 thr);
 
+/**
+ * ieee80211_sta_set_last_tx_bitrate - set last tx rate for station
+ *
+ * This sets the last TX bitrate for a given station.
+ *
+ * @sta: Pointer to the station
+ * @bitrate: Bitrate in kbps
+ */
+void ieee80211_sta_set_last_tx_bitrate(struct ieee80211_sta *sta, u32 bitrate);
+
 /**
  * ieee80211_tx_rate_update - transmit rate update callback
  *
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 05406e9c05b3..9de5390411ba 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -59,6 +59,10 @@  struct ieee80211_local;
 /* power level hasn't been configured (or set to automatic) */
 #define IEEE80211_UNSET_POWER_LEVEL	INT_MIN
 
+/* constants for calculating reciprocals to avoid division in fast path */
+#define IEEE80211_RECIPROCAL_DIVISOR 0x100000000ULL
+#define IEEE80211_RECIPROCAL_SHIFT 32
+
 /*
  * Some APs experience problems when working with U-APSD. Decreasing the
  * probability of that happening by using legacy mode for all ACs but VO isn't
diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index df553070206c..aae878ffe94c 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -2481,3 +2481,12 @@  void ieee80211_sta_set_expected_throughput(struct ieee80211_sta *pubsta,
 
 	sta_update_codel_params(sta, thr);
 }
+
+void ieee80211_sta_set_last_tx_bitrate(struct ieee80211_sta *pubsta,
+				       u32 rate)
+{
+	struct sta_info *sta = container_of(pubsta, struct sta_info, sta);
+
+	sta->last_tx_bitrate = rate;
+	sta->last_tx_bitrate_reciprocal = ((u64)IEEE80211_RECIPROCAL_DIVISOR / rate);
+}
diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index 369c2dddce52..dd1a0b87f234 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -617,6 +617,8 @@  struct sta_info {
 	const struct ieee80211_cipher_scheme *cipher_scheme;
 
 	struct codel_params cparams;
+	u32 last_tx_bitrate;
+	u64 last_tx_bitrate_reciprocal;
 
 	u8 reserved_tid;