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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5C9B6C2D0CD for ; Wed, 18 Dec 2019 12:22:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3308E227BF for ; Wed, 18 Dec 2019 12:22:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576671721; bh=mwUG7T4wiluvDMoa+8uM1MTApMMhiYa8/vECsa8OAxE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=aMCyLKzHLv7aWC58805t90YTSfhQOX5VyWa8UlrBwX2REr3W1GYctUCVnuIj6Irmc WTntPVy7GiCOU299Y9ukSvOLpqXNz/GcK22EuDBulXUsOxvuDPnRt6cfkEJjfkPQdk 5HGWpjYALC8FbRBYUBzTsKsHFYcObeSgRrM7WyHo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726937AbfLRMWA (ORCPT ); Wed, 18 Dec 2019 07:22:00 -0500 Received: from mail.kernel.org ([198.145.29.99]:44428 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725930AbfLRMWA (ORCPT ); Wed, 18 Dec 2019 07:22:00 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D114121582; Wed, 18 Dec 2019 12:21:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576671719; bh=mwUG7T4wiluvDMoa+8uM1MTApMMhiYa8/vECsa8OAxE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Ucr2Uf3eUh2mEBA62plUWANWmrqEmolSuEx8tTmm+okxdOQ13Aeegy8KhfAVwjKp9 72hB7zUnKvDuzwQM06zyPIoAuoX9th/aNWWQ1jnQ/LKYlqo0XUvfLfN1NQiqBZK23l qiG/XbRV18woNVgm8AnBtPO7Ztxa3rOPd3wJs3EA= Date: Wed, 18 Dec 2019 13:21:57 +0100 From: Greg KH To: Mark Brown Cc: Siddharth Kapoor , lee.jones@linaro.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: Kernel panic on Google Pixel devices due to regulator patch Message-ID: <20191218122157.GA17086@kroah.com> References: <20191218113458.GA3219@sirena.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191218113458.GA3219@sirena.org.uk> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 18, 2019 at 11:34:58AM +0000, Mark Brown wrote: > On Tue, Dec 17, 2019 at 11:51:55PM +0800, Siddharth Kapoor wrote: > > > I would like to share a concern with the regulator patch which is part of > > 4.9.196 LTS kernel. > > That's an *extremely* old kernel. It is, but it's the latest stable kernel (well close to), and your patch was tagged by you to be backported to here, so if there's a problem with a stable branch, I want to know about it as I don't want to see regressions happen in it. > > https://lore.kernel.org/lkml/20190904124250.25844-1-broonie@kernel.org/ > > That's the patch "[PATCH] regulator: Defer init completion for a while > after late_initcall" which defers disabling of idle regulators for a > while. > > Please include human readable descriptions of things like commits and > issues being discussed in e-mail in your mails, this makes them much > easier for humans to read especially when they have no internet access. > I do frequently catch up on my mail on flights or while otherwise > travelling so this is even more pressing for me than just being about > making things a bit easier to read. > > > We have reverted the patch in Pixel kernels and would like you to look into > > this and consider reverting it upstream as well. > > I've got nothing to do with the stable kernels so there's nothing I can > do here, sorry. Should I revert it everywhere? This patch reads as it should be fixing problems, not causing them :) > However if this is triggering anything it's almost > certainly some kind of timing issue (this code isn't new, it's just > being run a bit later) and is only currently working through luck so I > do strongly recommend trying to figure out the actual problem since it's > liable to come back and bite you later - we did find one buggy driver in > mainline as a result of this change, it's possible you've got another > one. > > Possibly your GPU supplies need to be flagged as always on, possibly > your GPU driver is forgetting to enable some supplies it needs, or > possibly there's a missing always-on constraint on one of the regulators > depending on how the driver expects this to work (if it's a proprietary > driver it shouldn't be using the regulator API itself). I'm quite > surprised you've not seen any issue before given that the supplies would > still be being disabled earlier. Timing "luck" is probably something we shouldn't be messing with in stable kernels. How about I revert this for the 4.14 and older releases and let new devices deal with the timing issues when they are brought up on new hardware? thanks, greg k-h