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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A2FDEC433F5 for ; Tue, 1 Mar 2022 12:19:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234687AbiCAMUJ (ORCPT ); Tue, 1 Mar 2022 07:20:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49438 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232613AbiCAMUG (ORCPT ); Tue, 1 Mar 2022 07:20:06 -0500 Received: from ni.piap.pl (ni.piap.pl [195.187.100.5]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 10E2A56C2C; Tue, 1 Mar 2022 04:19:22 -0800 (PST) Received: from t19.piap.pl (OSB1819.piap.pl [10.0.9.19]) by ni.piap.pl (Postfix) with ESMTPSA id D81C1C3F2A54; Tue, 1 Mar 2022 13:19:20 +0100 (CET) DKIM-Filter: OpenDKIM Filter v2.11.0 ni.piap.pl D81C1C3F2A54 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=piap.pl; s=mail; t=1646137161; bh=kSabZj2uSQjgkFczSZMvF3bJRihRCuN2IOOpNDYapls=; h=From:To:Cc:Subject:References:Date:In-Reply-To:From; b=npohYuiYKQrXVL3bxAXH92cQ4bKwu1JU2dbQkAHuNe2mbrOCzB4CGM7rSyiUvFgRi 00EWp3RezZb3EjsKrDNR0lV6Q7xFr80zE3T/6Zh2dj7UkGMlu4y8y4KfYtB54dAlxX 9Qnl2Rvf+QHYzZlTkCE9cMR7N7CVV+291V3beeIM= From: =?utf-8?Q?Krzysztof_Ha=C5=82asa?= To: Jacopo Mondi Cc: Mauro Carvalho Chehab , Rob Herring , devicetree@vger.kernel.org, linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, Laurent Pinchart , Sakari Ailus , Joe Perches Subject: Re: [PATCH v7 2/2] Driver for ON Semi AR0521 camera sensor References: <20220109153439.bfnfigocaeeeghmp@uno.localdomain> <20220301090132.g5xsodoeotcm6h2q@uno.localdomain> Sender: khalasa@piap.pl Date: Tue, 01 Mar 2022 13:19:20 +0100 In-Reply-To: <20220301090132.g5xsodoeotcm6h2q@uno.localdomain> (Jacopo Mondi's message of "Tue, 1 Mar 2022 10:01:32 +0100") Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-KLMS-Rule-ID: 3 X-KLMS-Message-Action: skipped X-KLMS-AntiSpam-Status: not scanned, whitelist X-KLMS-AntiPhishing: not scanned, whitelist X-KLMS-AntiVirus: Kaspersky Security for Linux Mail Server, version 8.0.3.30, not scanned, whitelist Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jacopo Mondi writes: >> They can. It appears, though, that clusters aren't about controls which >> can't change independently. Both of the two are written to the hardware >> at the same time, which appears to be a valid reason to combine them >> into a cluster. > > Is there a reason to write them to hw at the same time ? :) Sure, they are written in a single merged burst on I2C. > As it doesn't seem to me you access registers during probe (to > identify the sensor in example) there's no need to power up the device > during probe, but should be enough to let runtime_pm do so when > requested. Yes, in fact I never try to read anything from the sensor :-) Unfortunately I'm not sure how to initialize the (possibly nonexistent) PM without powering it up, cleanly, in all kernel configs. I mean, I can check if PM failed and power it up "by hand", but it's a bit messy. Suggestions are welcome, though. --=20 Krzysztof "Chris" Ha=C5=82asa Sie=C4=87 Badawcza =C5=81ukasiewicz Przemys=C5=82owy Instytut Automatyki i Pomiar=C3=B3w PIAP Al. Jerozolimskie 202, 02-486 Warszawa