Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754416AbdDNTMx (ORCPT ); Fri, 14 Apr 2017 15:12:53 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:54082 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754765AbdDNTMo (ORCPT ); Fri, 14 Apr 2017 15:12:44 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 6BCCD601D9 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=okaya@codeaurora.org Subject: Re: [PATCH V8 4/5] PCI/ASPM: save power on values during bridge init To: Rajat Jain References: <1491627351-1111-1-git-send-email-okaya@codeaurora.org> <1491627351-1111-5-git-send-email-okaya@codeaurora.org> Cc: linux-pci@vger.kernel.org, timur@codeaurora.org, "Patel, Mayurkumar" , linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Bjorn Helgaas , Yinghai Lu , David Daney , Shawn Lin , Julia Lawall , linux-kernel@vger.kernel.org, Rajat Jain From: Sinan Kaya Message-ID: Date: Fri, 14 Apr 2017 15:12:35 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1613 Lines: 36 Bjorn, On 4/12/2017 3:19 PM, Rajat Jain wrote: > On Fri, Apr 7, 2017 at 9:55 PM, Sinan Kaya wrote: >> Now that we added a hook to be called from device_add, save the >> default values from the HW registers early in the boot for further >> reuse during hot device add/remove operations. >> >> If the link is down during boot, assume that we want to enable L0s >> and L1 following hotplug insertion as well as L1SS if supported. > > IIUC, so far POLICY_DEFAULT meant that we'd just use & follow what > BIOS has done, and play it safe (never try to be more opportunistic). > With this change however, we'd be slightly overstepping and giving > ourselves benefit of doubt if the BIOS could not enable ASPM states > because the link was not up. This may be good, but I think we should > call it out, and add some more elaborate comment on the POLICY_DEFAULT > description (what to, and what not to expect in different situations). > > It is important because existing systems today, that used to boot > without cards and later hotplugged them, didn't have ASPM states > enabled. They will now suddenly start seeing all ASPM states enabled > including L1 substates for the first time (if supported). > Rajat has a good point here. Would you like me to update the ASPM document with this new behavior for hotplug? Do you have another behavior preference when it comes this? Sinan -- Sinan Kaya Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.