From 591980aaaa4645e6511f1387cc6092378a6bb84f Mon Sep 17 00:00:00 2001 From: Stanley Chu Date: Mon, 10 Aug 2026 09:30:59 +0800 Subject: [PATCH] i3c: master: allocate IBI workqueue with WQ_HIGHPRI MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Acked-by: Mukesh Kumar Savaliya Link: https://patch.msgid.link/20260810013059.3055787-1-yschu@nuvoton.com Signed-off-by: Alexandre Belloni --- 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 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;