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 74E95C4167B for ; Tue, 7 Nov 2023 15:27:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343629AbjKGP1W (ORCPT ); Tue, 7 Nov 2023 10:27:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60362 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234375AbjKGP1J (ORCPT ); Tue, 7 Nov 2023 10:27:09 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5F36C30C4 for ; Tue, 7 Nov 2023 07:26:38 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7E20CC433C7; Tue, 7 Nov 2023 15:26:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1699370798; bh=ljmnGxLYReiQWa6Iv86aTfS9zhxAvbUWtes+QtFunpE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=m63ny3zpg+SV/+cDpDbbJmMFdZ0EBKySKBGuQAqjxFNkqQGhaOdWSgvY56ZF7FxX5 kuHXtm0T3Wc4V1mbYpuqOn+x5n3xTZQtKiq/5u5bnCpOOZcQDSk8kE5CciAZ88Uh9/ aPKVARvlyxzu/U+Qj2T7+Sxos5JQIV3/OL2G8F1g= Date: Tue, 7 Nov 2023 16:26:34 +0100 From: Greg Kroah-Hartman To: Maxime Ripard Cc: Dmitry Baryshkov , Dave Stevenson , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Thomas Zimmermann , David Airlie , Daniel Vetter , Douglas Anderson , Rob Clark , Abhinav Kumar , Sean Paul , Marijn Suijten , Konrad Dybcio , Jessica Zhang , Marek Vasut , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org Subject: Re: [RFC PATCH 03/10] drm/mipi-dsi: add API for manual control over the DSI link power state Message-ID: <2023110704-deem-jigsaw-0bbf@gregkh> References: <20231016165355.1327217-4-dmitry.baryshkov@linaro.org> <7e4ak4e77fp5dat2aopyq3g4wnqu3tt7di7ytdr3dvgjviyhrd@vqiqx6iso6vg> <1696f131-83fb-4d0c-b4d7-0bdb61e4ae65@linaro.org> <2z3yvvtd6ttsd7qw43sl5svtfijxevdr6omxxmws64k6l5qv55@5nnh2b32h2ep> <2023110704-playback-grit-7a27@gregkh> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 07, 2023 at 01:18:14PM +0100, Maxime Ripard wrote: > On Tue, Nov 07, 2023 at 12:22:21PM +0100, Greg Kroah-Hartman wrote: > > On Tue, Nov 07, 2023 at 11:57:49AM +0100, Maxime Ripard wrote: > > > +GKH > > > > Why? I don't see a question for me here, sorry. > > I guess the question is: we have a bus with various power states > (powered off, low power, high speed) Great, have fun! And is this per-device or per-bus-instance? > low power is typically used to send commands to a device, high speed to > transmit pixels, but still allows to send commands. > > Depending on the devices, there's different requirements about the state > devices expect the bus to be in to send commands. Some will need to send > all the commands in the low power state, some don't care, etc. See > the mail I was replying too for more details. > > We've tried so far to model that in KMS itself, so the framework the > drivers would register too, but we're kind of reaching the limits of > what we can do there. It also feels to me that "the driver can't access > its device" is more of a problem for the bus to solve rather than the > framework. This is up to the specific bus to resolve, there's nothing special needed in the driver core for it, right? > Do you agree? Are you aware of any other bus in Linux with similar > requirements we could look at? Or any suggestion on how to solve it? There might be others, yes, look at how the dynamic power management works for different devices on most busses, that might help you out here. good luck! greg k-h