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 58B3FEE49AB for ; Wed, 23 Aug 2023 07:31:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233321AbjHWHbL (ORCPT ); Wed, 23 Aug 2023 03:31:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57516 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233319AbjHWHbL (ORCPT ); Wed, 23 Aug 2023 03:31:11 -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 E91DAE52; Wed, 23 Aug 2023 00:30:56 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 68422615B3; Wed, 23 Aug 2023 07:30:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E423CC433C7; Wed, 23 Aug 2023 07:30:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1692775855; bh=0BU5tvuZoETLLYAzQzR1sD8FFkPX6j54eFyEPsWBB3c=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=S6oVBX+c/AVyJt6WAVLtZ8XXBiSB2R0n/Y9V1xiyi/lJ02SycIsXE8WXobpe5Vbbu iqkiIyXxvkhczBoiglFGvXKBsmB0nOEZnY7ZEpBbsL2oOFbEogtmsux8iCl+ygFZ1m DSzI/tXpMaej4Rqkd+BiRGf4OkNXFc+aH9tdHH7FWJ7nax+uXdD9zLILElJt1n4mTn pqtLddxtsga5YZkSOfObuNqjUnvNRV4BLDLoi6Xh+5MbXb5UDRJQJYUlNl7R/DZvpd qGaLhJKrDeHXxiEF3heKSnfrUSGIgOqX6iaLsXCIeDJTkZi4VSAJ8eKW6vl2Pram/X ZDyLyKf55GB7w== Date: Wed, 23 Aug 2023 09:30:48 +0200 From: Lorenzo Pieralisi To: Jim Quinlan Cc: linux-pci@vger.kernel.org, Nicolas Saenz Julienne , Bjorn Helgaas , Lorenzo Pieralisi , Cyril Brulebois , Phil Elwell , bcm-kernel-feedback-list@broadcom.com, Jim Quinlan , Florian Fainelli , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , Rob Herring , Krzysztof Kozlowski , Conor Dooley , "moderated list:BROADCOM BCM7XXX ARM ARCHITECTURE" , "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , open list Subject: Re: [PATCH v6 1/5] dt-bindings: PCI: brcmstb: Add brcm,enable-l1ss property Message-ID: References: <20230623144100.34196-1-james.quinlan@broadcom.com> <20230623144100.34196-2-james.quinlan@broadcom.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Mon, Aug 21, 2023 at 12:01:50PM -0400, Jim Quinlan wrote: > On Mon, Aug 21, 2023 at 11:41 AM Lorenzo Pieralisi > wrote: > > > > On Mon, Aug 21, 2023 at 11:25:11AM -0400, Jim Quinlan wrote: > > > On Mon, Aug 21, 2023 at 10:47 AM Lorenzo Pieralisi > > > wrote: > > > > > > > > On Fri, Jun 23, 2023 at 10:40:54AM -0400, Jim Quinlan wrote: > > > > > This commit adds the boolean "brcm,enable-l1ss" property: > > > > > > > > > > The Broadcom STB/CM PCIe HW -- a core that is also used by RPi SOCs -- > > > > > requires the driver probe() to deliberately place the HW one of three > > > > > CLKREQ# modes: > > > > > > > > > > (a) CLKREQ# driven by the RC unconditionally > > > > > (b) CLKREQ# driven by the EP for ASPM L0s, L1 > > > > > (c) Bidirectional CLKREQ#, as used for L1 Substates (L1SS). > > > > > > > > > > The HW+driver can tell the difference between downstream devices that > > > > > need (a) and (b), but does not know when to configure (c). All devices > > > > > should work fine when the driver chooses (a) or (b), but (c) may be > > > > > desired to realize the extra power savings that L1SS offers. So we > > > > > introduce the boolean "brcm,enable-l1ss" property to inform the driver > > > > > that (c) is desired. Setting this property only makes sense when the > > > > > downstream device is L1SS-capable and the OS is configured to activate > > > > > this mode (e.g. policy==powersupersave). > > > > > > > > > > This property is already present in the Raspian version of Linux, but the > > > > > upstream driver implementation that follows adds more details and > > > > > discerns between (a) and (b). > > > > > > > > > > Signed-off-by: Jim Quinlan > > > > > Reviewed-by: Rob Herring > > > > > --- > > > > > Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml | 9 +++++++++ > > > > > 1 file changed, 9 insertions(+) > > > > > > > > > > diff --git a/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml b/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml > > > > > index 7e15aae7d69e..8b61c2179608 100644 > > > > > --- a/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml > > > > > +++ b/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml > > > > > @@ -64,6 +64,15 @@ properties: > > > > > > > > > > aspm-no-l0s: true > > > > > > > > > > + brcm,enable-l1ss: > > > > > + description: Indicates that PCIe L1SS power savings > > > > > + are desired, the downstream device is L1SS-capable, and the > > > > > + OS has been configured to enable this mode. For boards > > > > > > > > What does this mean ? I don't think DT properties are supposed > > > > to carry information related to how the OS is configured. > > > > > > The DT setting in question is unrelated to the statement "and the OS > > > has been configured to > > > enable this mode". > > > > > > This is merely saying that even if you enable "brcm,l1ss-enable" > > > that you may not get L1SS power savings w/o setting > > > "CONFIG_PCIEASPM_POWER_SUPERSAVE=y". > > > I mentioned that exact term but a reviewer nakked it because > > > apparently DT descriptions should not be OS specific. > > > > > > I am actually open for this to be a command-line option but I wanted to honor > > > what the Raspian OS folks have already done. RaspianOS already has > > > "brcm,enable-l1ss" > > > set in their DTS files. > > > > This is about the mainline kernel, I don't have any visibility into > > downstream kernels (where that property management was added without DT > > and PCI maintainers supervision). > > > > Raspian OS folks' choice is theirs but it can't and it shouldn't override > > the mainline review process even though I understand the position you > > are in. > > Understood, but using the command line has its warts as well; I now recall the > discussion Bjorn and I had regarding this option. I'm pretty sure > that upstreaam will not allow the following > possible command line kernel params: > > brcm,enable-l1ss > pci=brcm,entable-l1ss > > Bjorn suggested using the documented but (IMO) obscure and rarely > used format > > pci=[:]:.[/.]*pci::[::] > > but this is just going in the wrong direction; here's why. Using the > above iformat s completely dependent on the > PCI "linux-domaiin" property, a non-HW related DT property I might > add. Since "linux-domain" is already > a valid and well-used DT property, and the value of the above > command line format is dependent > on the value of the "linux-domain", why not be consistent and let > "brcm,enable-l1ss" be a Broadcom specific property? I am just asking to add a module_param to the host controller driver. Anyway - time is running out for v6.6, I need Rob's feedback, if I don't hear from him today I will merge the last three patches and postpone the discussion. Thanks, Lorenzo > > Regards, > Jim Quinlan > Broadcom STB/CM > > > > > > Thanks, > > Lorenzo > > > > > > > > Regards, > > > Jim > > > > > > > Again - it depends on what DT should be used for, I am not claiming to > > > > have any authority on that, just asking. > > > > > > > > Thanks, > > > > Lorenzo > > > > > > > > > + using a mini-card connector, this mode may not meet the > > > > > + TCRLon maximum time of 400ns, as specified in 3.2.5.2.2 > > > > > + of the PCI Express Mini CEM 2.0 specification. > > > > > + type: boolean > > > > > + > > > > > brcm,scb-sizes: > > > > > description: u64 giving the 64bit PCIe memory > > > > > viewport size of a memory controller. There may be up to > > > > > -- > > > > > 2.17.1 > > > > > > > > > > > > > > > > >