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=-7.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 2C1D1C43219 for ; Thu, 2 May 2019 09:05:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 03AA0206DF for ; Thu, 2 May 2019 09:05:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726385AbfEBJFM (ORCPT ); Thu, 2 May 2019 05:05:12 -0400 Received: from foss.arm.com ([217.140.101.70]:42414 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726203AbfEBJFM (ORCPT ); Thu, 2 May 2019 05:05:12 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 32E5E374; Thu, 2 May 2019 02:05:12 -0700 (PDT) Received: from e107155-lin (e107155-lin.cambridge.arm.com [10.1.196.42]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9D5893F5AF; Thu, 2 May 2019 02:05:10 -0700 (PDT) Date: Thu, 2 May 2019 10:05:08 +0100 From: Sudeep Holla To: Sodagudi Prasad Cc: julien.thierry@arm.com, will.deacon@arm.com, catalin.marinas@arm.com, mark.rutland@arm.com, lorenzo.pieralisi@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: PSCI version 1.1 and SYSTEM_RESET2 Message-ID: <20190502090507.GC12498@e107155-lin> References: <24970f7101952f347bd4046c9a980473@codeaurora.org> <20190501094953.GA21851@e107155-lin> <3ceb06c36ecb745e2befaeaefe49be19@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3ceb06c36ecb745e2befaeaefe49be19@codeaurora.org> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 01, 2019 at 11:43:00AM -0700, Sodagudi Prasad wrote: > On 2019-05-01 02:49, Sudeep Holla wrote: > > On Tue, Apr 30, 2019 at 05:07:31PM -0700, Sodagudi Prasad wrote: > > > On 2019-04-30 14:44, Sodagudi Prasad wrote: [...] > > > > > > It would nice if there is a config option to reboot the device > > > either in > > > warm or cold in the case of kernel panic. > > > > I presume you prefer to do warm boot in case of panic to get a dump of > > the memory to inspect ? If so, is kexec/kdump not the mechanism to > > achieve that ? > > Hi Sudeep, > > Thanks for your response and sharing details about your patch. > > > If so, is kexec/kdump not the mechanism to achieve that? > > > Qualcomm is having vendor specific solution to capture ram contents and for > offline analysis. > Ah OK. > > > > I am just trying to understand the use case. Xilinx asked for the same > > but never got to understand their use case. > > Here is the background - > Usually, power off drivers are overriding arm_pm_restart and pm_power_off > callbacks and registering with reboot notifier with some priority for the > reboot operations. Here is the Qualcomm poweroff driver for reference. > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/power/reset/msm-poweroff.c > > Before vendor chip set specific power off driver is probed, arm_pm_restart > functions pointer holds the psci_sys_reset function. Once vendor power off > driver is probed, vendor drivers can override the arm_pm_restart function > pointer. > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/firmware/psci.c#n562 > > Once vendor driver is probed, drivers can take care of devices warm or hard > reset configuration part properly. But there is a window from > start_kernel() to vendor specific driver probed, devices are getting cold > resets even if kernel crashed. This is due to arm_pm_restart points to > psci_sys_reset function by default. Is this problem clear now? > Too specific use case IMO and I am not sure if we need a generic solution to deal with this. Anyways, I don't see any check in arch/psci specific code for what you want, just ensure reboot_mode is set appropriately. Post a patch and see what people have to say. > Qualcomm downstream kernel has a lot of use cases with respect device reset > sequence and the downstream driver is much different from upstream drivers. > I think, the above-mentioned problem is common for all the chipset vendors > and it is not specific Qualcomm use cases. I have one downstream solution > to this problem but thought to bring up this problem to the upstream > community for a common solution, so that all the vendors can use it. > May be or may be not, post the patch and let's see. > I have modified below flow to avoid cold restart in the case of early kernel > panic. > panic() --> emergency_restart() --> machine_emergency_restart() --> > machine_restart(NULL); > > -Thanks, Prasad > > > > > -- > > Regards, > > Sudeep > > -- > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, > Linux Foundation Collaborative Project