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([2a02:810d:15c0:828:49e6:bb8c:a05b:c4ed]) by smtp.gmail.com with ESMTPSA id p7-20020a170906838700b009484e17e7f5sm1135463ejx.100.2023.04.06.11.54.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 06 Apr 2023 11:54:50 -0700 (PDT) Message-ID: Date: Thu, 6 Apr 2023 20:54:49 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [PATCH v1 1/3] dt-bindings: PCI: brcmstb: Add two optional props Content-Language: en-US To: Florian Fainelli , Jim Quinlan , linux-pci@vger.kernel.org, Nicolas Saenz Julienne , Bjorn Helgaas , Lorenzo Pieralisi , Cyril Brulebois , Phil Elwell , bcm-kernel-feedback-list@broadcom.com, james.quinlan@broadcom.com Cc: Lorenzo Pieralisi , =?UTF-8?Q?Krzysztof_Wilczy=c5=84ski?= , Rob Herring , Krzysztof Kozlowski , "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" , "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , open list References: <20230406124625.41325-1-jim2101024@gmail.com> <20230406124625.41325-2-jim2101024@gmail.com> <9e98496b-73a0-78a5-e890-7d7e4be1f469@gmail.com> From: Krzysztof Kozlowski In-Reply-To: <9e98496b-73a0-78a5-e890-7d7e4be1f469@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/04/2023 20:53, Florian Fainelli wrote: > On 4/6/23 11:34, Krzysztof Kozlowski wrote: >> On 06/04/2023 14:46, Jim Quinlan wrote: >>> Regarding "brcm,enable-l1ss": >>> >>> The Broadcom STB/CM PCIe HW -- which is also used by RPi SOCs -- requires >>> the driver probe to configure one of three clkreq# modes: >>> >>> (a) clkreq# driven by the RC >>> (b) clkreq# driven by the EP for ASPM L0s, L1 >>> (c) bidirectional clkreq#, as used for L1 Substates (L1SS). >>> >>> The HW can tell the difference between (a) and (b), but does not know >>> when to configure (c). Further, the HW will cause a CPU abort on boot if >>> guesses wrong regarding the need for (c). So we introduce the boolean >>> "brcm,enable-l1ss" property to indicate that (c) is desired. This >>> property is already present in the Raspian version of Linux, but the >>> driver implementaion that will follow adds more details and discerns >>> between (a) and (b). >>> >>> Regarding "brcm,completion-timeout-msecs" >>> >>> Our HW will cause a CPU abort if the L1SS exit time is longer than the >>> completion abort timeout. We've been asked to make this configurable, so >>> we are introducing "brcm,completion-abort-msecs". >>> >>> Signed-off-by: Jim Quinlan >>> --- >>> .../devicetree/bindings/pci/brcm,stb-pcie.yaml | 12 ++++++++++++ >>> 1 file changed, 12 insertions(+) >>> >>> diff --git a/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml b/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml >>> index 7e15aae7d69e..ef4ccc05b258 100644 >>> --- a/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml >>> +++ b/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml >>> @@ -64,6 +64,18 @@ properties: >>> >>> aspm-no-l0s: true >>> >>> + brcm,enable-l1ss: >>> + description: Indicates that the downstream device is L1SS >>> + capable and L1SS is desired, e.g. by setting >>> + CONFIG_PCIEASPM_POWER_SUPERSAVE=y. Note that CLKREQ# >> >> How does CONFIG_PCIEASPM_POWER_SUPERSAVE apply to *BSD? > > In other words, there should be no OS/Linux specific comments in a > Device Tree binding, which would be a friendlier and nicer way of > providing the same feedback. I want to give also the answer also why there should be no OS/Linux specific comments, so the reader can stop a bit and think about it :) Best regards, Krzysztof