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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8FE40C001B5 for ; Fri, 2 Sep 2022 17:24:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236553AbiIBRYJ (ORCPT ); Fri, 2 Sep 2022 13:24:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39062 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235976AbiIBRYH (ORCPT ); Fri, 2 Sep 2022 13:24:07 -0400 Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 47E721151A2; Fri, 2 Sep 2022 10:24:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1662139446; x=1693675446; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=DSWKIZICL0ryGmE0f8bau1LNf2o5POsf7uXeN32Zn08=; b=MJJemxq9gj+p5FLZoWNDp3SYFUWB7o18CrzSeMsn95blFaCCD713RgKf WvmVD756gjnn13Mvf58ZkyrD2mTpIq8+6aJPQsL8rOENKzu96DKyQg7SE IC4C/QOEvdDl8jmSkdu6np4OjPbpt2/33ideKrOzbaiPakLC6XwblVlJa J/DestAZpXYK7quu1ShCvPJ4TGMEFkxFSaJliVZBQ74tE6lBtqLhGjHMV MaPB0fbIx1tq/ZVNd4UG5+345dkvYF+VtPtLEeX0P3cPgazB3QiGpKiDw KvW5xWxp/Nqc3/91mPOPIj3B4q7FFCJfwEg0QATxLMgJN9cFspFEottry g==; X-IronPort-AV: E=McAfee;i="6500,9779,10458"; a="294771178" X-IronPort-AV: E=Sophos;i="5.93,283,1654585200"; d="scan'208";a="294771178" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Sep 2022 10:24:06 -0700 X-IronPort-AV: E=Sophos;i="5.93,283,1654585200"; d="scan'208";a="674435558" Received: from cthornbr-mobl.amr.corp.intel.com (HELO [10.251.3.254]) ([10.251.3.254]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Sep 2022 10:24:05 -0700 Message-ID: Date: Fri, 2 Sep 2022 10:24:05 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Firefox/91.0 Thunderbird/91.11.0 Subject: Re: [PATCH 1/4] PCI/PTM: Preserve PTM Root Select Content-Language: en-US To: Bjorn Helgaas , Kai-Heng Feng , Rajvi Jingar , "Rafael J . Wysocki" Cc: Koba Ko , Mika Westerberg , "David E . Box" , linux-pci@vger.kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Bjorn Helgaas References: <20220902145835.344302-1-helgaas@kernel.org> <20220902145835.344302-2-helgaas@kernel.org> From: Sathyanarayanan Kuppuswamy In-Reply-To: <20220902145835.344302-2-helgaas@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/2/22 7:58 AM, Bjorn Helgaas wrote: > From: Bjorn Helgaas > > When disabling PTM, there's no need to clear the Root Select bit. We > disable PTM during suspend, and we want to re-enable it during resume. > Clearing Root Select here makes re-enabling more complicated. Currently, it looks like we disable PCI_PTM_CTRL_ROOT in pci_disable_ptm(), but not enable it in pci_enable_ptm(). Do you know this did not trigger an issue? Also, you mentioned that it is complicated to enable it, can you add some details? > > Per PCIe r6.0, sec 7.9.15.3, "When set, if the PTM Enable bit is also Set, > this Time Source is the PTM Root," so if PTM Enable is cleared, the value > of Root Select should be irrelevant. > > Preserve Root Select to simplify re-enabling PTM. > > Signed-off-by: Bjorn Helgaas > Cc: David E. Box > --- > drivers/pci/pcie/ptm.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/pci/pcie/ptm.c b/drivers/pci/pcie/ptm.c > index 368a254e3124..b6a417247ce3 100644 > --- a/drivers/pci/pcie/ptm.c > +++ b/drivers/pci/pcie/ptm.c > @@ -42,7 +42,7 @@ void pci_disable_ptm(struct pci_dev *dev) > return; > > pci_read_config_word(dev, ptm + PCI_PTM_CTRL, &ctrl); > - ctrl &= ~(PCI_PTM_CTRL_ENABLE | PCI_PTM_CTRL_ROOT); > + ctrl &= ~PCI_PTM_CTRL_ENABLE; > pci_write_config_word(dev, ptm + PCI_PTM_CTRL, ctrl); > } > -- Sathyanarayanan Kuppuswamy Linux Kernel Developer