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| author | Stanley Chu <yschu@nuvoton.com> | 2026-08-10 09:30:59 +0800 |
|---|---|---|
| committer | Alexandre Belloni <alexandre.belloni@bootlin.com> | 2026-09-17 16:51:06 +0200 |
| commit | 591980aaaa4645e6511f1387cc6092378a6bb84f (patch) | |
| tree | 3ecb3d07dca52770ee012ef995f4d2316f6426f7 | |
| parent | cee9395acd8043be0644b25c34bfa86623f2b935 (diff) | |
| download | linux-next-591980aaaa4645e6511f1387cc6092378a6bb84f.tar.gz linux-next-591980aaaa4645e6511f1387cc6092378a6bb84f.zip | |
i3c: master: allocate IBI workqueue with WQ_HIGHPRI
The IBI (In-Band Interrupt) workqueue is allocated with only
WQ_MEM_RECLAIM, which places IBI payload processing at normal
worker priority. This is inadequate given the time-sensitive
nature of IBI handling.
In the I3C protocol, when a target asserts an IBI, the SDA line
is held low until the master acknowledges and completes the
exchange. The IRQ handler (top half) ACKs the IBI, reads the
payload, emits a STOP, and immediately queues the payload
processing to the per-device ordered workqueue via
i3c_master_queue_ibi() — effectively the bottom half of the
IBI interrupt path.
If this workqueue worker is delayed by competing normal-priority
tasks, the IBI notification reaches the client driver late. For
latency-sensitive clients (e.g. sensors reporting alerts,
hotplug events), this defeats the purpose of using IBI over
polling. Furthermore, because the ordered workqueue serialises
slots, a backlog of delayed slots can exhaust the pre-allocated
IBI slot pool, causing subsequent IBIs to be dropped at the
hardware level.
Add WQ_HIGHPRI to ensure IBI bottom-half work is scheduled
promptly after the top-half IRQ handler enqueues it, keeping
the IBI processing pipeline consistent with the interrupt-like
semantics the protocol demands.
Signed-off-by: Stanley Chu <yschu@nuvoton.com>
Acked-by: Mukesh Kumar Savaliya <mukesh.savaliya@oss.qualcomm.com>
Link: https://patch.msgid.link/20260810013059.3055787-1-yschu@nuvoton.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
| -rw-r--r-- | drivers/i3c/master.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c index afcd7a21a3e6..4fa90013290f 100644 --- a/drivers/i3c/master.c +++ b/drivers/i3c/master.c @@ -3945,7 +3945,8 @@ int i3c_dev_request_ibi_locked(struct i3c_dev_desc *dev, if (!ibi) return -ENOMEM; - ibi->wq = alloc_ordered_workqueue(dev_name(i3cdev_to_dev(dev->dev)), WQ_MEM_RECLAIM); + ibi->wq = alloc_ordered_workqueue(dev_name(i3cdev_to_dev(dev->dev)), + WQ_MEM_RECLAIM | WQ_HIGHPRI); if (!ibi->wq) { kfree(ibi); return -ENOMEM; |