From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sinan Kaya Subject: Re: [PATCH V8 4/5] PCI/ASPM: save power on values during bridge init Date: Fri, 14 Apr 2017 15:12:35 -0400 Message-ID: References: <1491627351-1111-1-git-send-email-okaya@codeaurora.org> <1491627351-1111-5-git-send-email-okaya@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-pci-owner@vger.kernel.org To: Rajat Jain 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 List-Id: linux-arm-msm@vger.kernel.org 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. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-Path: 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> From: Sinan Kaya Message-ID: Date: Fri, 14 Apr 2017 15:12:35 -0400 MIME-Version: 1.0 In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Patel, Mayurkumar" , Rajat Jain , David Daney , linux-pci@vger.kernel.org, timur@codeaurora.org, linux-kernel@vger.kernel.org, Julia Lawall , linux-arm-msm@vger.kernel.org, Bjorn Helgaas , Yinghai Lu , Shawn Lin , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+bjorn=helgaas.com@lists.infradead.org List-ID: 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. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel From mboxrd@z Thu Jan 1 00:00:00 1970 From: okaya@codeaurora.org (Sinan Kaya) Date: Fri, 14 Apr 2017 15:12:35 -0400 Subject: [PATCH V8 4/5] PCI/ASPM: save power on values during bridge init In-Reply-To: References: <1491627351-1111-1-git-send-email-okaya@codeaurora.org> <1491627351-1111-5-git-send-email-okaya@codeaurora.org> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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.