[PATCH v1] i3c: master: allocate IBI workqueue with WQ_HIGHPRI
Stanley Chu <[email protected]>
| Newsgroups | org.infradead.lists.linux-i3c,org.kernel.vger.linux-kernel |
|---|---|
| Message-ID | <[email protected]> |
From: Stanley Chu <[email protected]> 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 <[email protected]> --- drivers/i3c/master.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c index f1be38a640ca..8fdd67a031ff 100644 --- a/drivers/i3c/master.c +++ b/drivers/i3c/master.c @@ -3505,7 +3505,8 @@ 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; -- 2.34.1 -- linux-i3c mailing list [email protected] http://lists.infradead.org/mailman/listinfo/linux-i3c