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 EF8C2ECAAD1 for ; Tue, 30 Aug 2022 16:25:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229633AbiH3QZe (ORCPT ); Tue, 30 Aug 2022 12:25:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52010 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229453AbiH3QZe (ORCPT ); Tue, 30 Aug 2022 12:25:34 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9208D7F13B; Tue, 30 Aug 2022 09:25:32 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 308D4616EC; Tue, 30 Aug 2022 16:25:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5DEC3C433D6; Tue, 30 Aug 2022 16:25:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1661876731; bh=fX7lFkw2y3pdMg4VZBDhdTZbmlADf2lW89e/h6BNv1Q=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=gWSU5o/BDYQwHOOxA02WWMV7MiZJmwdgbPkYtqDMwpL9jaf4xEeUh8/W3mjsKlwV9 536yo7lJeLyxr6edq9HHeX1l+Qw2bAyNIMPUBP413iGqYGOO2TVOrKwmZJjoHi/+vN mS1OyMzZ187YZEvSlxBCmmgRVIVIJc/pyLt+8qQIyvqnC2f47W3HUVWcTGIr7ZzkN4 B/BWvbqo/ipODa3NCTJ31jYqVmrbJ6J7h9PHuwqyJm+cfm08ra3+Jth+EfK82jHVoz PjJTtjLoNm/4xzm2C5Y8CH2tCfnSCGKKyWtdCN0xijCiGElR1Svfs0vVHnpr1uwJPP TpzxXPI0GR5ag== Date: Tue, 30 Aug 2022 11:25:29 -0500 From: Bjorn Helgaas To: Rajvi Jingar Cc: rafael.j.wysocki@intel.com, bhelgaas@google.com, david.e.box@linux.intel.com, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Kai-Heng Feng Subject: Re: [RESEND PATCH v3 2/2] PCI/PTM: fix to maintain pci_dev->ptm_enabled Message-ID: <20220830162529.GA106073@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220830104913.1620539-2-rajvi.jingar@linux.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org [+cc Kai-Heng] On Tue, Aug 30, 2022 at 03:49:13AM -0700, Rajvi Jingar wrote: > pci_dev->ptm_enabled needs to be maintained to reflect the current PTM > state of the device. In pci_ptm_disable(), clear ptm_enabled from > 'struct pci_dev' on disabling PTM state for the device. > In pci_restore_ptm_state(), set dev->ptm_enabled based on the restored > PTM state of the device. > > In pci_ptm_disable(), perform ptm_enabled check to avoid config space > access in case if PTM is already disabled for the device. ptm_enabled > won't be set for non-PCIe devices so pci_is_pcie(dev) check is not > needed anymore. This one sounds like it's supposed to fix something, but I'm not clear exactly what. I have a vague memory of config accesses messing up a low power state. But this is still completely magical and unmaintainable since AFAIK there is nothing in the PCIe spec about avoiding config accesses when PTM is disabled. At the very least, we would need more details in the commit log and a hint in the code about this. > Signed-off-by: Rajvi Jingar > Reviewed-by: Rafael J. Wysocki > --- > v1->v2: > - add ptm_enabled check in pci_ptm_disable(). > - set the dev->ptm_enabled value in pci_restore_ptm_state(). > v2->v3: > - remove pci_is_pcie(dev) check in pci_ptm_disable(). > - add Reviewed-by tag in commit message > --- > drivers/pci/pcie/ptm.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/pcie/ptm.c b/drivers/pci/pcie/ptm.c > index 368a254e3124..1ce241d4538f 100644 > --- a/drivers/pci/pcie/ptm.c > +++ b/drivers/pci/pcie/ptm.c > @@ -34,7 +34,7 @@ void pci_disable_ptm(struct pci_dev *dev) > int ptm; > u16 ctrl; > > - if (!pci_is_pcie(dev)) > + if (!dev->ptm_enabled) > return; This will conflict with a change Kai-Heng Feng and I have been working on, but I can resolve it when applying. > ptm = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_PTM); > @@ -44,6 +44,7 @@ void pci_disable_ptm(struct pci_dev *dev) > pci_read_config_word(dev, ptm + PCI_PTM_CTRL, &ctrl); > ctrl &= ~(PCI_PTM_CTRL_ENABLE | PCI_PTM_CTRL_ROOT); > pci_write_config_word(dev, ptm + PCI_PTM_CTRL, ctrl); > + dev->ptm_enabled = 0; > } > > void pci_save_ptm_state(struct pci_dev *dev) > @@ -83,6 +84,7 @@ void pci_restore_ptm_state(struct pci_dev *dev) > > cap = (u16 *)&save_state->cap.data[0]; > pci_write_config_word(dev, ptm + PCI_PTM_CTRL, *cap); > + dev->ptm_enabled = !!(*cap & PCI_PTM_CTRL_ENABLE); > } > > void pci_ptm_init(struct pci_dev *dev) > -- > 2.25.1 >