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 1D93AEE49B0 for ; Wed, 23 Aug 2023 14:49:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236660AbjHWOtA (ORCPT ); Wed, 23 Aug 2023 10:49:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53832 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234019AbjHWOs6 (ORCPT ); Wed, 23 Aug 2023 10:48:58 -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 ADC36E69; Wed, 23 Aug 2023 07:48:56 -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 3F7C5635B5; Wed, 23 Aug 2023 14:48:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5FB62C43397; Wed, 23 Aug 2023 14:48:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1692802135; bh=/mIR/BoeNsGIQ35vEJiMSnGRE9NkIijQbN8TMPht8lA=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=JBv45U/ckigIhCoTgbnPxY3Ny4JXMfYMJCeyqcKL7v+4wHcK/eJQ9W+ASwoffbDAh spSkMl0KWiaQ6cPaocfiphUqOrcmQ7vSO2Ej39BAIP0+vH/R22Go282M7Ey8r3tWHv e3aa6Fjmlb1Ki1fJ2MCLJePdWG2gdv5kwfQPoKhbRJbyygnUwfb/eXr6BTyDTnvQ+Y PwuKQBDRYU+JMnhe7ZoI89O4xb7Q6sFGHsm68tsuvX4Ddx1bp1aRq5ZRqE0plciE+i Cggq1nw3xI4wQpGBYT3vXwj92L878Dfahl8lIf2gzZ5Pr9YC8whpYgA87LqaXoYdeL SKgVCvl3TrrHQ== Received: by mail-lj1-f169.google.com with SMTP id 38308e7fff4ca-2b9bb097c1bso87672951fa.0; Wed, 23 Aug 2023 07:48:55 -0700 (PDT) X-Gm-Message-State: AOJu0Yyvc/SE3nMCj82UfZIxXqFcYiA2y16rRgrDk7AnZ6EBUtowYXwS 3drAU9fN8QmmeGwi9ECGZ52Brv7CIfPYmj5BrQ== X-Google-Smtp-Source: AGHT+IHMstTvKJFQFHSGfZa/sGOrQBVC6gBZtEcBjOgKF3HFClPHqsTsD0J+JzNdiJCbkccX59siSGCFrcffdxYYF1A= X-Received: by 2002:a2e:978c:0:b0:2bc:bb3e:1abe with SMTP id y12-20020a2e978c000000b002bcbb3e1abemr7588725lji.41.1692802133206; Wed, 23 Aug 2023 07:48:53 -0700 (PDT) MIME-Version: 1.0 References: <20230623144100.34196-1-james.quinlan@broadcom.com> <20230623144100.34196-2-james.quinlan@broadcom.com> In-Reply-To: From: Rob Herring Date: Wed, 23 Aug 2023 09:48:40 -0500 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v6 1/5] dt-bindings: PCI: brcmstb: Add brcm,enable-l1ss property To: Lorenzo Pieralisi Cc: Jim Quinlan , 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 , =?UTF-8?Q?Krzysztof_Wilczy=C5=84ski?= , 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 23, 2023 at 2:30=E2=80=AFAM Lorenzo Pieralisi wrote: > > On Mon, Aug 21, 2023 at 12:01:50PM -0400, Jim Quinlan wrote: > > On Mon, Aug 21, 2023 at 11:41=E2=80=AFAM Lorenzo Pieralisi > > wrote: > > > > > > On Mon, Aug 21, 2023 at 11:25:11AM -0400, Jim Quinlan wrote: > > > > On Mon, Aug 21, 2023 at 10:47=E2=80=AFAM 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 RP= i 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 devi= ces that > > > > > > need (a) and (b), but does not know when to configure (c). A= ll 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 t= he 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=3D=3Dpowersupersave). > > > > > > > > > > > > This property is already present in the Raspian version of Li= nux, 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-pci= e.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 O= S > > > > 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=3Dy". > > > > I mentioned that exact term but a reviewer nakked it because > > > > apparently DT descriptions should not be OS specific. Yeah, probably the OS part should be dropped. > > > > > > > > I am actually open for this to be a command-line option but I wante= d 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 over= ride > > > the mainline review process even though I understand the position you > > > are in. Sure, but we shouldn't change things just to be different from downstream. If we're only discussing the color of the shed, then no point changing it. > > > > Understood, but using the command line has its warts as well; I now rec= all 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=3Dbrcm,entable-l1ss > > > > Bjorn suggested using the documented but (IMO) obscure and rarely > > used format > > > > pci=3D[:]:.[/.]*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. FWIW, gregkh pretty much always nacks new module parameters. > > 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. You've already got my reviewed-by. If you aren't happy with this, then fine. I don't know enough about L1SS to comment further. Is it normally always supported or discoverable? If so, then I'd think we'd want it default enabled with a disable override flag. Maybe it should be generic? Rob