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bluez5: iso-io: track and apply corrections to tx latency

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Use TX timestamps to get accurate reading of queue length and latency on
kernel + controller side.

This is new kernel BT feature, so requires kernel with the necessary
patches, available currently only in bluetooth-next/master branch.
Enabling Poll Errqueue kernel experimental Bluetooth feature is also
required for this.

Use the latency information to mitigate controller issues where ISO
streams are desynchronized due to tx problems or spontaneously when some
packets that should have been sent are left sitting in the queue, and
transmission is off by a multiple of the ISO interval.  This state is
visible in the latency information, so if we see streams in a group have
persistently different latencies, drop packets to resynchronize them.

Also make corrections if the kernel/controller queues get too long, so
that we don't have too big latency there.

Since BlueZ watches the same socket for errors, and TX timestamps arrive
via the socket error queue, we need to set BT_POLL_ERRQUEUE in addition
to SO_TIMESTAMPING so that BlueZ doesn't think TX timestamps are errors.

Link: https://github.com/bluez/bluez/issues/515
Link: https://lore.kernel.org/linux-bluetooth/cover.1710440392.git.pav@iki.fi/
Link: https://lore.kernel.org/linux-bluetooth/f57e065bb571d633f811610d273711c7047af335.1712499936.git.pav@iki.fi/
This commit is contained in:
Pauli Virtanen 2024-02-20 23:01:07 +02:00
parent 9165291c43
commit a6dcdfae0c
7 changed files with 298 additions and 23 deletions
Download patch file Download diff file Expand all files Collapse all files

14
spa/plugins/bluez5/rate-control.h
View file

@ -19,10 +19,11 @@ struct spa_bt_ptp
int32_t maxs[4];
};
uint32_t pos;
uint32_t left;
uint32_t period;
};
static inline void spa_bt_ptp_init(struct spa_bt_ptp *p, int32_t period)
static inline void spa_bt_ptp_init(struct spa_bt_ptp *p, int32_t period, uint32_t min_duration)
{
size_t i;
@ -31,6 +32,7 @@ static inline void spa_bt_ptp_init(struct spa_bt_ptp *p, int32_t period)
p->mins[i] = INT32_MAX;
p->maxs[i] = INT32_MIN;
}
p->left = min_duration;
p->period = period;
}
@ -54,6 +56,16 @@ static inline void spa_bt_ptp_update(struct spa_bt_ptp *p, int32_t value, uint32
p->mins[n-1] = INT32_MAX;
p->maxs[n-1] = INT32_MIN;
}
if (p->left < duration)
p->left = 0;
else
p->left -= duration;
}
static inline bool spa_bt_ptp_valid(struct spa_bt_ptp *p)
{
return p->left == 0;
}
/**