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

From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
To: Florian Fainelli <f.fainelli@gmail.com>,
	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>,
	"Krzysztof Wilczyński" <kw@linux.com>,
	"Rob Herring" <robh@kernel.org>,
	"Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
	"moderated list:BROADCOM BCM7XXX ARM ARCHITECTURE"
	<linux-arm-kernel@lists.infradead.org>,
	"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE"
	<linux-rpi-kernel@lists.infradead.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
	<devicetree@vger.kernel.org>,
	"open list" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 1/3] dt-bindings: PCI: brcmstb: Add two optional props
Date: Wed, 12 Apr 2023 13:56:30 +0200	[thread overview]
Message-ID: <66b7d0b9-9569-ddaf-89ca-5a0133074a17@linaro.org> (raw)
In-Reply-To: <78c18cdb-5757-8d30-e2a6-414f09505cc6@gmail.com>

On 12/04/2023 13:49, Florian Fainelli wrote:
> 
> 
> On 4/12/2023 1:09 AM, Krzysztof Kozlowski wrote:
>> 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@gmail.com>
>>
>> What happened here? Where is the changelog?
> 
> It is in the cover letter:
> 
> https://lore.kernel.org/all/20230411165919.23955-1-jim2101024@gmail.com/
> 
> but it does not look like the cover letter was copied to you or Rob.

As you said, I did not get it.

Best regards,
Krzysztof