linux-kernel - Re: [PATCH v2 1/3] dt-bindings: PCI: brcmstb: Add two optional props

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Message-ID: <5a28e520-63e4-dbcf-5b3e-e5097f02dea2@linaro.org>
Date:   Wed, 12 Apr 2023 10:09:05 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Jim Quinlan <jim2101024@...il.com>, linux-pci@...r.kernel.org,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Cyril Brulebois <kibi@...ian.org>,
        Phil Elwell <phil@...pberrypi.com>,
        bcm-kernel-feedback-list@...adcom.com, james.quinlan@...adcom.com
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        "moderated list:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-rpi-kernel@...ts.infradead.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] dt-bindings: PCI: brcmstb: Add two optional props

On 11/04/2023 18:59, Jim Quinlan wrote:
> Regarding "brcm,enable-l1ss":
> 
>   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).  Further, the
>   HW may 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.  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==superpowersave).
> 
>   This property is already present in the Raspian version of Linux, but the
>   upstream driver implementaion that will follow adds more details and

typo, implementation

>   discerns between (a) and (b).
> 
> Regarding "brcm,completion-timeout-us"
> 
>   Our HW will cause a CPU abort if the L1SS exit time is longer than the
>   PCIe transaction completion abort timeout.  We've been asked to make this
>   configurable, so we are introducing "brcm,completion-timeout-us".
> 
> Signed-off-by: Jim Quinlan <jim2101024@...il.com>

What happened here? Where is the changelog?

Best regards,
Krzysztof