From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga03.intel.com ([134.134.136.65]:57828 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726784AbeJSTvm (ORCPT ); Fri, 19 Oct 2018 15:51:42 -0400 Subject: Re: [PATCH] PCI / PM: Allow runtime PM without callback functions To: Bjorn Helgaas Cc: linux-pci@vger.kernel.org, linux-pm@vger.kernel.org, Bjorn Helgaas , "Rafael J . Wysocki" , Mika Westerberg , Jean Delvare , Wolfram Sang , stable@vger.kernel.org References: <20181018123038.21386-1-jarkko.nikula@linux.intel.com> <20181018212513.GM5906@bhelgaas-glaptop.roam.corp.google.com> From: Jarkko Nikula Message-ID: Date: Fri, 19 Oct 2018 14:45:54 +0300 MIME-Version: 1.0 In-Reply-To: <20181018212513.GM5906@bhelgaas-glaptop.roam.corp.google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: stable-owner@vger.kernel.org List-ID: On 10/19/2018 12:25 AM, Bjorn Helgaas wrote: > On Thu, Oct 18, 2018 at 03:30:38PM +0300, Jarkko Nikula wrote: >> Allow PCI core to do runtime PM to devices without needing to use dummy >> runtime PM callback functions if there is no need to do anything device >> specific beyond PCI device power state management. >> >> Implement this by letting core to change device power state during >> runtime PM transitions even if no callback functions are defined. >> >> Fixes: a9c8088c7988 ("i2c: i801: Don't restore config registers on runtime PM") >> Reported-by: Mika Westerberg >> Cc: > > I applied this with Rafael's reviewed-by to pci/misc for v4.20, > thanks! > > But I dropped the stable tag because if I understand correctly, the > point of this is to avoid the need for SIMPLE_DEV_PM_OPS() in drivers > that don't need to do anything for PM. > > That's worthwhile, but it's not transparently obvious that it would > qualify for a stable backport based on this: > > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/stable-kernel-rules.rst > > If there's an argument for adding a stable tag, I'll add it , but that > justification should be explicit in the changelog. > No disagreement here. I was thinking a second or two before sending the patch may I Cc or not the stable. I went adding it since this actually fixes a PM regression on i2c-i801 after v4.18. SMBus PCI device doesn't go to D3 and /sys/bus/pci/devices/[0000:00:1f.3 etc]/power/runtime_status shows "error" when runtime PM framework attempts to autosuspend the device. But given that most of the platforms I have seen don't implement the PM capabilities for SMBus PCI device, a few do implement though, and we haven't got any regression reports either so this is not very fatal IMHO. I definitely don't want to see massive regression from different PCI systems either. Queueing for v4.20 sounds reasonable and we can ask to cherry-pick the commit into v4.18 and v4.19 stable kernels if nothing fatal shows up. -- Jarkko