From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AE129C35646 for ; Fri, 21 Feb 2020 13:25:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8BFD6206D7 for ; Fri, 21 Feb 2020 13:25:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728630AbgBUNZR (ORCPT ); Fri, 21 Feb 2020 08:25:17 -0500 Received: from foss.arm.com ([217.140.110.172]:39280 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727213AbgBUNZR (ORCPT ); Fri, 21 Feb 2020 08:25:17 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BD74730E; Fri, 21 Feb 2020 05:25:16 -0800 (PST) Received: from [10.37.12.243] (unknown [10.37.12.243]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 315133F703; Fri, 21 Feb 2020 05:25:14 -0800 (PST) Subject: Re: [RFC PATCH v2 07/13] firmware: arm_scmi: Add notification dispatch and delivery To: Cristian Marussi , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: sudeep.holla@arm.com, james.quinlan@broadcom.com, Jonathan.Cameron@Huawei.com References: <20200214153535.32046-1-cristian.marussi@arm.com> <20200214153535.32046-8-cristian.marussi@arm.com> From: Lukasz Luba Message-ID: Date: Fri, 21 Feb 2020 13:25:12 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20200214153535.32046-8-cristian.marussi@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Cristian, I didn't want to jump into your discussion with Jim in other broader thread with this small thought, so I added a comment below. On 2/14/20 3:35 PM, Cristian Marussi wrote: > Add core SCMI Notifications dispatch and delivery support logic which is > able, at first, to dispatch well-known received events from the RX ISR to > the dedicated deferred worker, and then, from there, to final deliver the > events to the registered users' callbacks. > > Dispatch and delivery is just added here, still not enabled. > > Signed-off-by: Cristian Marussi > --- > V1 --> V2 > - splitted out of V1 patch 04 > - moved from IDR maps to real HashTables to store event_handlers > - simplified delivery logic > --- > drivers/firmware/arm_scmi/notify.c | 242 ++++++++++++++++++++++++++++- > drivers/firmware/arm_scmi/notify.h | 22 +++ > 2 files changed, 262 insertions(+), 2 deletions(-) > > diff --git a/drivers/firmware/arm_scmi/notify.c b/drivers/firmware/arm_scmi/notify.c > index 1339b6de0a4c..c2341c5304cf 100644 > --- a/drivers/firmware/arm_scmi/notify.c > +++ b/drivers/firmware/arm_scmi/notify.c > @@ -48,13 +48,44 @@ > * particular event coming only from a well defined source (like CPU vs GPU). > * When the source is not specified the user callback will be registered for > * all existing sources for that event (if any). [snip] > > @@ -840,6 +1071,11 @@ static struct scmi_notify_ops notify_ops = { > */ > int scmi_notification_init(struct scmi_handle *handle) > { > + scmi_notify_wq = alloc_workqueue("scmi_notify", > + WQ_UNBOUND | WQ_FREEZABLE, 0); I think it might limit some platforms. It depends on their workload. If they have some high priority workloads which rely on this mechanisms, they might need a RT task here. The workqueues would be scheduled in CFS, so it depends on workload in there (we might even see 10s ms delays in scheduling-up them). If we use RT we would grab the CPU from CFS. It would be good if it is a customization option: which mechanism to use based on some a parameter. Then we could create: a) workqueue with the flags above b) workqueue with WQ_HIGHPRI (limited by minimum nice) c) kthread_create_worker() with RT/DL/FIFO sched policy (with also a parameterized priority) In default clients might use a) but when they want to tune their platform, they might change only a parameter in their scmi code, not maintaining a patch for the RT function out of tree. Regards, Lukasz