From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay6-d.mail.gandi.net (relay6-d.mail.gandi.net [217.70.183.198]) (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 3E95C1DA28 for ; Fri, 20 Oct 2023 14:33:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bootlin.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b="IVVDGU/4" Received: by mail.gandi.net (Postfix) with ESMTPSA id C94A7C0007; Fri, 20 Oct 2023 14:33:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=gm1; t=1697812429; 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=zZPwG1QrAqBLq23wnEyxrPXk3d8fu1E8yL0jWfm6ZX4=; b=IVVDGU/4ju4RloomC3TVhl6poOqo447GqE9kialVEV+1EUAbwOf3wpNP97tzIe+DfRl9JC MW6imyQzM2HcFGIOG+t3RVSwKcs5jkH74R8jNHHxznmOuP/9gFhkE4ypfvRoAW6zpkghyP YqJPQPpgB1515Fov8LwSy5amH/TXkv9+tjNjR6wsg2BHAj4EqVDzAIojmONee1EpXZNecQ m5bgzefIWvqBkM23swIYEitTpZcLkuJxVvnH/41MtStoI4HUneRuX1HwkfJ5JRykT/VyWL GTkWB3gU0P5syaaxmGbuk6/Ufk/30zeKB3yhtpUkgiWpjXHQXge7LlHuqpG23Q== Date: Fri, 20 Oct 2023 16:33:48 +0200 From: Miquel Raynal To: Frank Li Cc: "Zbigniew, Lukwinski" , alexandre.belloni@bootlin.com, 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: <20231020163348.1752167d@xps-13> In-Reply-To: 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> Organization: Bootlin X-Mailer: Claws Mail 4.0.0 (GTK+ 3.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: imx@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-GND-Sasl: miquel.raynal@bootlin.com 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, > >=20 > > zbigniew.lukwinski@linux.intel.com wrote on Fri, 20 Oct 2023 10:55:27 > > +0200: > > =20 > > > On 10/18/2023 10:59 PM, Frank Li wrote: =20 > > > > Add hotjoin entry in sys file system allow user enable/disable hotj= oin > > > > feature. > > > > > > > > Add (*enable(disable)_hotjoin)() to i3c_master_controller_ops. > > > > Add api i3c_master_enable(disable)_hotjoin(); =20 > > >=20 > > > 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 rea= lly need to enable/disable HJ in runtime for other reason but debug? If it = is only for debug maybe it=C2=A0 could be move to debugFS? =20 > >=20 > > 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 handle > > an IBI) whereas if your design is "fixed" (more like an I2C bus) you > > may save power by disabling this feature. > >=20 > > A module parameter does not fit here because it's a per-bus > > configuration. =20 >=20 > 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. Thanks, Miqu=C3=A8l