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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C03EAC001DF for ; Fri, 20 Oct 2023 20:25:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=7vALKbdL8P4hBBvRcrY+rszcvSiXZNmqFkOdiDpNC4A=; b=TwQ5fZkFt0XeKL gxgOiA5qpx7Fm+k2CPMO+fJmpAqgrJ9Zyl+FzkhXBztTWm+V+EHQo1c9i103SVhhK9s8T1mavb5fU BqsOhj0q29bs2om1RkY3Thuyc2Rdl265Iw0zUqAmrzxr351JfgQT321uJ2eABmFwBdmZ7q5RrpYP7 SfYHbKSDa0ypRqhXt83CTuju+UUCAnY7SzylLJbsCzjHuvai8eodapJhQy7h5OdyZ9H0K8WdcH/zn eplwZDY2YNCG/sYpZzZqSsR80Isq8ypO8qQsCfUIUIp3tZcyivT6Lkje7YakmgdDme3y3cfEi0WjB YAPg8SPmBYMpi0jDUPug==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qtw3o-002yTl-0E; Fri, 20 Oct 2023 20:25:32 +0000 Received: from relay4-d.mail.gandi.net ([2001:4b98:dc4:8::224]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qtw3k-002ySE-0X for linux-i3c@lists.infradead.org; Fri, 20 Oct 2023 20:25:30 +0000 Received: by mail.gandi.net (Postfix) with ESMTPSA id B6A9CE0003; Fri, 20 Oct 2023 20:25:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=gm1; t=1697833520; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=sfiWF1djQwW183R/n1Ql11Gvhq6s/Znqmh+4YVfuGWU=; b=lmMEKHcO4Kfebn4Ds5bXoJ7JSSdHmrZVL0PjwehYTgvNmjc0wbpbssC5t6ldsPBp7LuHKt hwu2U9DK6qnP1764Y3xC+dEUESkCTPTjHEWANuEofysAwrEZWB9Ztm3hzbnSaoWSisDl85 Knb7vG4qL9rZ+gqij5IqasMyIYBnheXqXN1TAEbsOLZlxm35tNxXmBuj4Caus2EVjMrHrz QL78DZXcXfbAmF5VHe3diLW6dxyHQ8oyTdJZVD5+VQCwlkYvjHXi2GOEHieXEl7CSsM0nd 5P5OUbDVxXNeEIupFx9uPcFeTokOY+ABWFENSlsxCr6QG+osKNzGNDbSMIp1NA== Date: Fri, 20 Oct 2023 22:25:19 +0200 From: Alexandre Belloni To: "Zbigniew, Lukwinski" Cc: Miquel Raynal , Frank Li , conor.culhane@silvaco.com, imx@lists.linux.dev, joe@perches.com, linux-i3c@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/6] i3c: master: add enable(disable) hot join in sys entry Message-ID: <20231020202519b2449707@mail.local> References: <20231018205929.3435110-1-Frank.Li@nxp.com> <20231018205929.3435110-2-Frank.Li@nxp.com> <57efe6de-cf65-32ed-fd1e-a388e1676c70@linux.intel.com> <20231020154528.2f5f68f5@xps-13> <20231020163348.1752167d@xps-13> <8a7ac52e-f102-6f5e-35ab-217e6ecc6ba5@linux.intel.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <8a7ac52e-f102-6f5e-35ab-217e6ecc6ba5@linux.intel.com> X-GND-Sasl: alexandre.belloni@bootlin.com X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231020_132528_533689_AAA3F01E X-CRM114-Status: GOOD ( 28.21 ) X-BeenThere: linux-i3c@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sender: "linux-i3c" Errors-To: linux-i3c-bounces+linux-i3c=archiver.kernel.org@lists.infradead.org On 20/10/2023 17:12:53+0200, Zbigniew, Lukwinski wrote: > On 10/20/2023 4:33 PM, Miquel Raynal wrote: > > Hi Frank, > > = > > Frank.li@nxp.com wrote on Fri, 20 Oct 2023 10:20:57 -0400: > > = > > > On Fri, Oct 20, 2023 at 03:45:28PM +0200, Miquel Raynal wrote: > > > > Hi Lukwinski, > > > > = > > > > zbigniew.lukwinski@linux.intel.com wrote on Fri, 20 Oct 2023 10:55= :27 > > > > +0200: > > > > > On 10/18/2023 10:59 PM, Frank Li wrote: > > > > > > Add hotjoin entry in sys file system allow user enable/disable = hotjoin > > > > > > feature. > > > > > > = > > > > > > Add (*enable(disable)_hotjoin)() to i3c_master_controller_ops. > > > > > > Add api i3c_master_enable(disable)_hotjoin(); > > > > > What is the use case for having HJ enable knob in sysfs available= for user space other than for debug stuff? In other words, does user space= really need to enable/disable HJ in runtime for other reason but debug? If= it is only for debug maybe it=A0 could be move to debugFS? > > > > I don't think hotjoin should be considered as a debug feature. The > > > > problem here is the power consumption which is higher if you enable > > > > this feature (you need to keep everything clocked and ready to hand= le > > > > an IBI) whereas if your design is "fixed" (more like an I2C bus) you > > > > may save power by disabling this feature. > > > > = > > > > A module parameter does not fit here because it's a per-bus > > > > configuration. > > > I agree. sys entry is more flexiable. and let controller choose better > > > power saving policy for difference user case. > > Maybe it's not the first time this case is faced, would you mind > > including power management maintainers in this discussion? Perhaps they > > might have pointers or even have the solution already. > = > I did not mind HJ as debug feature. But enabling / disabling the HJ sounds > to me like debug option. > = > So the flow you are considering here is like this:? > = > 1. system boot with HJ enabled, so HJ works during initial bus > discovery > 2. some entity in user space decides to disable HJ because power > consumption? > 3. some entity in use space decide some time later to re-enable HJ > because some reason? > = > I am just wondering whether there is real use case when you starts with HJ > enabled and than disable it > = > in runtime or start with HJ disabled and enable it in runtime. If you are > taking care about power saving > = > =A0let's keep HJ disabled all the time. Default state for HJ could be > controlled by DT entry. > = This would be HW configuration and not HW description. > = > > Thanks, > > Miqu=E8l -- = Alexandre Belloni, co-owner and COO, Bootlin Embedded Linux and Kernel engineering https://bootlin.com -- = linux-i3c mailing list linux-i3c@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-i3c