Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <9e98496b-73a0-78a5-e890-7d7e4be1f469@gmail.com>
Date:   Thu, 6 Apr 2023 11:53:19 -0700
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:     Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
        Jim Quinlan <jim2101024@gmail.com>, linux-pci@vger.kernel.org,
        Nicolas Saenz Julienne <nsaenz@kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Cyril Brulebois <kibi@debian.org>,
        Phil Elwell <phil@raspberrypi.com>,
        bcm-kernel-feedback-list@broadcom.com, james.quinlan@broadcom.com
Cc:     Lorenzo Pieralisi <lpieralisi@kernel.org>,
        =?UTF-8?Q?Krzysztof_Wilczy=c5=84ski?= <kw@linux.com>,
        Rob Herring <robh@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-rpi-kernel@lists.infradead.org>,
        "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-arm-kernel@lists.infradead.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>
References: <20230406124625.41325-1-jim2101024@gmail.com>
 <20230406124625.41325-2-jim2101024@gmail.com>
 <ebde318b-53be-6779-4f0c-a614c01a0b0a@linaro.org>
From:   Florian Fainelli <f.fainelli@gmail.com>
In-Reply-To: <ebde318b-53be-6779-4f0c-a614c01a0b0a@linaro.org>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

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 <jim2101024@gmail.com>
>> ---
>>   .../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.
-- 
Florian