From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx0b-0031df01.pphosted.com (mx0b-0031df01.pphosted.com [205.220.180.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BB8E8339391 for ; Mon, 10 Aug 2026 18:27:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=205.220.180.131 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786386475; cv=none; b=WBmBTDKie6GYHw4lCtJU5oAFuWsz9cnpDm/d4O7iPg42aXBeLtni/3cUFI6Pj+G98mKlZiyGjerTufP2xH3Qr6iIgLGYgSMtnBTjQTcWkBiIkICBsUXzCTXJPMltv5f4LVWlnuoaG04CzlU/eu7KS9FvPNR0ZF2X49x4qkRF/uA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786386475; c=relaxed/simple; bh=AFNsLcZQ9ITWhYhTO/rFZlp4Pcg/N8ajTjYP086IxLg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=R3IfS5UABioyV+AkOyMMFNrYa0MrnIwJO2weAiHjsVi1UxYbvdFEpQbCc+aqLG8p695ObHiuQEhSF3v98mtTXu7ztLFuiHRwpDlXnTf7MEuSXCjRA922tU9EfKRbHHPZqflRbdkKyEqkVRFRCOWY9spwdqA4P7AQ+gquDZlDHN4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=oss.qualcomm.com; spf=pass smtp.mailfrom=oss.qualcomm.com; dkim=pass (2048-bit key) header.d=qualcomm.com header.i=@qualcomm.com header.b=X5BrowNF; dkim=pass (2048-bit key) header.d=oss.qualcomm.com header.i=@oss.qualcomm.com header.b=XJwgyqRV; arc=none smtp.client-ip=205.220.180.131 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=oss.qualcomm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=oss.qualcomm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=qualcomm.com header.i=@qualcomm.com header.b="X5BrowNF"; dkim=pass (2048-bit key) header.d=oss.qualcomm.com header.i=@oss.qualcomm.com header.b="XJwgyqRV" Received: from pps.filterd (m0279869.ppops.net [127.0.0.1]) by mx0a-0031df01.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 67AGDwZR880822 for ; Mon, 10 Aug 2026 18:27:52 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=qualcomm.com; h= cc:content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s=qcppdkim1; bh= 2O8FxR7lrAEjoX7u/9TIYcjqIEX5JTXw9wgl/N7/Nl4=; b=X5BrowNFVBP3pjKV Zwqsn3pRgU3LrhXOzmEW8jLf3oglJwORNGyeBG5TlTqpS/tbno4Lm5GzPoqOiLZG 0LRQwdl9t9iXZ8SQJguRERX9cVMbA5zn6z7wXY/+jm9MJvEbE4JhQNJR1R88TC12 UmdZr+rDaa4JdhqTSciO+/qumLQA+fLtvPz0tSqhecwPOJhmIYVGuoQB2wdJsm9B eKqPvZdvh6UVIiFj8feQJmGaNOSi/9UmTRnTJaY+MpPnYmWvnBV26qDTUbnoUu6x ODNJZF4HhZ/t6UXhGTjwrCMLgMaPCws/jcktzcwhtLaRJrR37hjXAcBhj089Accm uwdvNQ== Received: from mail-pg1-f200.google.com (mail-pg1-f200.google.com [209.85.215.200]) by mx0a-0031df01.pphosted.com (PPS) with ESMTPS id 4fycget6pb-1 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NOT) for ; Mon, 10 Aug 2026 18:27:52 +0000 (GMT) Received: by mail-pg1-f200.google.com with SMTP id 41be03b00d2f7-c9c26587e67so194941a12.0 for ; Mon, 10 Aug 2026 11:27:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oss.qualcomm.com; s=google; t=1786386472; x=1786991272; darn=vger.kernel.org; h=content-transfer-encoding:content-type:in-reply-to:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:from:to:cc:subject:date:message-id:reply-to :content-type; bh=2O8FxR7lrAEjoX7u/9TIYcjqIEX5JTXw9wgl/N7/Nl4=; b=XJwgyqRVHNIxBqrfrAlFbprnIG/01kMgCLbX2ga3A7SChaw5QWNNq3BPyWY4kx6g1F W7NHpGKcqHTfT6cDWQAuDg7joyjI9qzNXC1IKNBgcTYqXnsTCoUPolQ0L4ShChPThC0c bA896YjvFy5tXLlG2MU9XEvlIIEeGDZOC5WWVowvPrfGY66QlGrsqMwxbVvVgzpvNKZ0 jCvMDGkfhKEmHEwaeonkkvXTjN/3D55H+PW+L1vqoK2UvOeI5gglqnyr18M7w7dq9W/8 a6cfF0PlZLy5Oyo3pWw+XM07W9jx3yUBqghdtdFNC/EmQtE9Z+oRorT5MmSiYFnnG2YA DH7Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786386472; x=1786991272; h=content-transfer-encoding:content-type:in-reply-to:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=2O8FxR7lrAEjoX7u/9TIYcjqIEX5JTXw9wgl/N7/Nl4=; b=eeObtsv21PRra2ugEc5u0T9T0lrCTFFnLcH2u8FNZxc5z58lmsjtOg0dd43WYlFvCo DdC472dK6tkHKEd7kpPm2gfjyw6YXxRp5joqdpvWKhD6XBJsyx1QrQd/M584BVt5nr8F UdAMfgrJQtj76BTsIpHPuKdJ3dbM/0hMWoJF9ZIQns3WZcWFs4G1chLeX0kgPNi7SHco 4v/v/cQb3v9K8eQxhTdKU86reM3gR+MMvI7IxuEsyiq7UUwNMRFWN/+ZHLUoc8qaxw5X DOnDwl3s8cCLPsXQj6akzvDWRP9oMrYJCBxtRxF2qPcxPkqw9Y0iLzOyzTp4YL/DtNFy 6gdg== X-Gm-Message-State: AOJu0YzFqLkuQgYDSqSUXEbb9K1Mm4mMU9+su9l5lSUz+g2IfmSRrJjV jXqiMdRuhVZl1TBHyvc6NGqzN7g3RTrDwW2J4HV0UFpsabG0+KFDgoMvG8CHoXzE6xF8O+Pdmf4 havgkbDTtmM2y9HvCEo1Qsm6NZ+7Mgvdjb1XSbj6lNra4ErYUOh3uY52jcSN2n8/XLEQ= X-Gm-Gg: AR+sD10H9FfxQqxOKIk4pUnTPGgbjNqbwGcM40q8egfTl3XCU0+qMyDafrNrUY/L9TX M/43VgFQKV+RkbWlTHNdD16mwovyEWyVQvqy46dJgxPlnjcQr31rP7oF7+rpMsdhLOJcPS2LSUA 1trKyA5oYbmszV54TMn2xzcFARGBqGi6m66581LhlhX9Rycq6+1e2Iw1eAB6lBzbSqql4p6/ZxS cow7afjKWMW1Xm2pEkaMexjV5Pek6AYRt83KDjtmj+IQcYfhlOfX9eqMtZuWdN1y+fjC/UF20au gKDAzwFKmn43O7y5X9/L/YPzsPklnr/76jybph4v/KHZu3QF1wOcuEcXT8SNbfCt0mnfQtVE3MO HFiMr/A/qFMl6WTwoUz1lJU7zLpZMxO5awSw= X-Received: by 2002:a05:6a20:3ca3:b0:3bf:b7e8:68ab with SMTP id adf61e73a8af0-3cc22d69259mr563617637.2.1786386471555; Mon, 10 Aug 2026 11:27:51 -0700 (PDT) X-Received: by 2002:a05:6a20:3ca3:b0:3bf:b7e8:68ab with SMTP id adf61e73a8af0-3cc22d69259mr563551637.2.1786386471002; Mon, 10 Aug 2026 11:27:51 -0700 (PDT) Received: from [192.168.1.8] ([106.222.230.104]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-14101b7ad29sm36569895c88.13.2026.08.10.11.27.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 10 Aug 2026 11:27:50 -0700 (PDT) Message-ID: Date: Mon, 10 Aug 2026 23:57:44 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1] i3c: master: allocate IBI workqueue with WQ_HIGHPRI To: Stanley Chu , frank.li@nxp.com, miquel.raynal@bootlin.com, alexandre.belloni@bootlin.com, linux-i3c@lists.infradead.org Cc: linux-kernel@vger.kernel.org, tomer.maimon@nuvoton.com, kwliu@nuvoton.com, yschu@nuvoton.com References: <20260810013059.3055787-1-yschu@nuvoton.com> Content-Language: en-US From: Mukesh Savaliya In-Reply-To: <20260810013059.3055787-1-yschu@nuvoton.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Proofpoint-ORIG-GUID: rs6W0EgadBCPyJRASwicnewRIvEDSXZF X-Authority-Analysis: v=2.4 cv=R4cz39RX c=1 sm=1 tr=0 ts=6a7a1828 cx=c_pps a=oF/VQ+ItUULfLr/lQ2/icg==:117 a=hsRoOqe6K9Dtf6G3Ghy1+w==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=_glEPmIy2e8OvE2BGh3C:22 a=BxgfbMJPAAAA:8 a=EUspDBNiAAAA:8 a=pP_cOjKy0jrMBpLy9EEA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=3WC7DwWrALyhR5TkjVHa:22 a=-j4ASRGczZqhCHD74e4j:22 X-Proofpoint-GUID: rs6W0EgadBCPyJRASwicnewRIvEDSXZF X-Proofpoint-Spam-Info: AW1haW4tMjYwODEwMDE1OCBTYWx0ZWRfX5e2RYo4bmQJt MEAOypgzkl72+7lklFbJk5Ob3H3fOGX8ibwmqGBSYmYvtBAlqwRRE5UgV5Vdkgffrr/R0oerUyA Brsk76zzqI3xJC94K3UF/fEzIATJlXM= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODEwMDE1OCBTYWx0ZWRfX7AV6AdkB1WuK Z1XeN01dednL08JahsWFreZV0lyXp82dx1QpaCtc/JrIdaQFdYFrHnbhOHg8m6gIhlZ6ugpFLMz TVK5xue72bVC8nn/voyxwETiXhcwUM0PWeYfmEMuMeJPv4UMfUFqQsfXHjFU1Cd4Adqwq2bI9Kz TDyAcN5P/7Gt2cu8Wm8VY8whtnp6Ru4mxLHdZAE1LYmSCS1UeSbNgaVpa1gdIpLTx47LWcGuUZd 8KJYjG9e47Cf5J9l/MIUfAcVF1hJfAjF5wd3NroyqmQNPpyI9LeQzDm+MZO981EWsuf8hA2JnpG nQWIqhPJlVwvAphIYALUzkrNFrFY675uxSwtljYNmO5xV44mIE5rQ0M6rN5J4/uSKTBmj9RL+2F CGqM3PwfvPXeF5IWIDft3yymbauOPhMBeHfxV7Z2gQZZTsyPBzTb/uvzxO4Bu+GTQcMGESlupSL VHKyYx7C9fLctJZYNYQ== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-10_04,2026-08-10_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 adultscore=0 malwarescore=0 priorityscore=1501 bulkscore=0 suspectscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608100158 On 8/10/2026 7:00 AM, Stanley Chu wrote: > From: Stanley Chu > > 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