From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 03AF73E5EC7; Wed, 27 May 2026 09:06:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779872820; cv=none; b=UupQck3CZ+9DFq7pD3tViekgF6+iIKXqYLzQC1NuTBpr6T/ZerHG4QkRqooSXaXmfUMjgCUSEOkcL/O54z+AR7Rg0KKuRdsIzRcHOqPCQBo8n1vmEl+SdtPYT8VnZ04uc7tkdCJaMJIUWHr/gf3aYVdBPnnSYeo/V8mpqPA0jA4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779872820; c=relaxed/simple; bh=OQVJZfwHpXN0n/v7h29x/cHNl444YSA1UCol0sqqDpM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=PDc61mwv2X2632KVqmvLoMYffwx2w4vgfnecJQC+CAIurc/3UKk6LALNfVnYEqDtrOhhNMJVuXJ/6/gBZLp1+oQnJ5+rsc7A2Q5l89CzcDqym/ocMExC5Svso/GxbjX4nO2ddHnkHcB8wZq7Uc7TVxIAD8IHMUklVJ0G7lC6ItQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=nkMAgueW; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="nkMAgueW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9AE9A1F000E9; Wed, 27 May 2026 09:06:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779872818; bh=Ka6yC3QrHcEkiDk7alcfHWrv6N92oBkr2LoopdWzh7Q=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=nkMAgueWuwGVRv0HOVp+lcKpTELX8upnzcUnPp3tNS1p4S4x3iB0NS5KSyHXzMvnZ aU5hGJKwUyxUBQw9g7fSNZ5y5tcrYKNLK3B6/rwV6+3HeuuxhcBz2ZX/F9pUWTbYEs YBXBgRwY6uB7lRQlxxo4kXrb8nMhy0IW616dPfsdF77zbHaCcp8btD4JhIBUMknHW5 d4MeuIJM7GJ6F9oDQ4lwUHJ54+SaJ0awD7/Q+RHUMGNY2hz/iqIRk0dcT6pWDCChqm s7UovzhkqzWyRU6o+5nu0ShMvqjiHijzNY+q6XTIE8y5xkfFep41mW8bJMOwb8w2ql lnOkwlcwQq+JQ== Message-ID: Date: Wed, 27 May 2026 12:06:52 +0300 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 9/9] arm64: dts: renesas: rzg3s-smarc-som: Enable I3C To: Wolfram Sang Cc: geert+renesas@glider.be, linusw@kernel.org, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, magnus.damm@gmail.com, claudiu.beznea@tuxon.dev, linux-renesas-soc@vger.kernel.org, linux-gpio@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Claudiu Beznea References: <20260522102251.1723392-1-claudiu.beznea@kernel.org> <20260522102251.1723392-10-claudiu.beznea@kernel.org> Content-Language: en-US From: Claudiu Beznea In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hi, Wolfram, On 5/26/26 19:55, Wolfram Sang wrote: > Hi Claudiu, > >> Could you please let me know what do you consider we should do here? Do you >> think we could drop these pin controller setting and do some particular I3C >> controller settings instead? > > My original thought was: If it was a boolean state which is active when > suspending and disabled when resuming, then we wouldn't need a customer > specific binding for it and just do this in the suspend/resume functions > of the pin-controller... > > ... BUT ... > > reading more about this in the manual, just raises more questions for > me. > >> The output is fixed at Hi-Z and no data is transmitted to the inside even if >> data is input from outside. “Standby mode” is available when using I2C mode >> only. (Not available when using I3C mode). >> >> The current driver proposal don't take into account the IP mode when setting >> STBN though >> pinctrl_pm_select_sleep_state()/pinctrl_pm_select_default_state() to keep >> the code simpler, relying on the "Not available when using I3C mode" part of >> the note, and considering setting it when the IP is in I3C mode is harmless. > > This is one question I also had: What does "not available" actually > mean? Did you confirm with HW guys that it is really harmles? I asked this yesterday, but I don't have an answer to it. In my testing I haven't noticed any issues with it. > > I also wonder about the intended use-case of this mode. "no data is > transmitted to the inside even if data is input from outside" doesn't > really sound like a mode intended when the whole SoC goes to sleep. Indeed, that's why I chose in the driver to touch it though the runtime PM APIs, so it can be configured after the I3C IP is no longer used. > Why > or how would input be even transmitted to the inside if everything is in > a deep-sleep state? I could also imagine that this mode is rather used > to hide from the bus for a while for some corner-case reason. > > And finally: does this really save energy? I don't expect. I'm not sure I can measure it. I also asked to the HW team. > Could you measure a benefit? > Maybe there is nothing driven at all in the sleep state? Then, nothing > is gained? Not clear from the datasheet. > > Because the datasheet is so sparse with information and because it > doesn't say how STBN is intended to be used, I would argue we should > skip it until we know what it is for and how it is used. If we know this > somewhen, we can still add this in a second step. OK for me. > > But for now, enabling I3C realiably is the first step, and for that we > surley need the POC bit to select the voltage. This is easily > understandable and straightforward to do. So, my suggestion is to pick > this low-hanging fruit now and reach for the other one once we have more > information about it. OK, I'll re-spin this dropping the STBN feature until further clarification. -- Thank you, Claudiu