linux-kernel - Re: [PATCH v8 0/2] PCI: brcmstb: Configure appropriate HW CLKREQ# mode

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Message-ID: <20240111115646.GA1443933@rocinante>
Date: Thu, 11 Jan 2024 20:56:46 +0900
From: Krzysztof Wilczyński <kw@...ux.com>
To: Jim Quinlan <james.quinlan@...adcom.com>
Cc: 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,
	Conor Dooley <conor+dt@...nel.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" <devicetree@...r.kernel.org>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Jim Quinlan <jim2101024@...il.com>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" <linux-arm-kernel@...ts.infradead.org>,
	open list <linux-kernel@...r.kernel.org>,
	"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" <linux-rpi-kernel@...ts.infradead.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Rob Herring <robh@...nel.org>
Subject: Re: [PATCH v8 0/2] PCI: brcmstb: Configure appropriate HW CLKREQ#
 mode

Hello,

> V8 -- Un-advertise L1SS capability when in "no-l1ss" mode (Bjorn)
>    -- Squashed last two commits of v7 (Bjorn)
>    -- Fix DT binding description text wrapping (Bjorn)
>    -- Fix incorrect Spec reference (Bjorn)
>          s/PCIe Spec/PCIe Express Mini CEM 2.1 specification/
>    -- Text substitutions (Bjorn)
>          s/WRT/With respect to/ 
>          s/Tclron/T_CLRon/
> 
> v7 -- Manivannan Sadhasivam suggested (a) making the property look like a
>       network phy-mode and (b) keeping the code simple (not counting clkreq
>       signal appearances, un-advertising capabilites, etc).  This is
>       what I have done.  The property is now "brcm,clkreq-mode" and
>       the values may be one of "safe", "default", and "no-l1ss".  The
>       default setting is to employ the most capable power savings mode.
> 
> v6 -- No code has been changed.
>    -- Changed commit subject and comment in "#PERST" commit (Bjorn, Cyril)
>    -- Changed sign-off and author email address for all commits.
>       This was due to a change in Broadcom's upstreaming policy.
> 
> v5 -- Remove DT property "brcm,completion-timeout-us" from	 
>       "DT bindings" commit.  Although this error may be reported	 
>       as a completion timeout, its cause was traced to an	 
>       internal bus timeout which may occur even when there is	 
>       no PCIe access being processed.  We set a timeout of four	 
>       seconds only if we are operating in "L1SS CLKREQ#" mode.
>    -- Correct CEM 2.0 reference provided by HW engineer,
>       s/3.2.5.2.5/3.2.5.2.2/ (Bjorn)
>    -- Add newline to dev_info() string (Stefan)
>    -- Change variable rval to unsigned (Stefan)
>    -- s/implementaion/implementation/ (Bjorn)
>    -- s/superpowersave/powersupersave/ (Bjorn)
>    -- Slightly modify message on "PERST#" commit.
>    -- Rebase to torvalds master
> 
> v4 -- New commit that asserts PERST# for 2711/RPi SOCs at PCIe RC
>       driver probe() time.  This is done in Raspian Linux and its
>       absence may be the cause of a failing test case.
>    -- New commit that removes stale comment.
> 
> v3 -- Rewrote commit msgs and comments refering panics if L1SS
>       is enabled/disabled; the code snippet that unadvertises L1SS
>       eliminates the panic scenario. (Bjorn)
>    -- Add reference for "400ns of CLKREQ# assertion" blurb (Bjorn)
>    -- Put binding names in DT commit Subject (Bjorn)
>    -- Add a verb to a commit's subject line (Bjorn)
>    -- s/accomodat(\w+)/accommodat$1/g (Bjorn)
>    -- Rewrote commit msgs and comments refering panics if L1SS
>       is enabled/disabled; the code snippet that unadvertises L1SS
>       eliminates the panic scenario. (Bjorn)
> 
> v2 -- Changed binding property 'brcm,completion-timeout-msec' to
>       'brcm,completion-timeout-us'.  (StefanW for standard suffix).
>    -- Warn when clamping timeout value, and include clamped
>       region in message. Also add min and max in YAML. (StefanW)
>    -- Qualify description of "brcm,completion-timeout-us" so that
>       it refers to PCIe transactions. (StefanW)
>    -- Remvove mention of Linux specifics in binding description. (StefanW)
>    -- s/clkreq#/CLKREQ#/g (Bjorn)
>    -- Refactor completion-timeout-us code to compare max and min to
>       value given by the property (as opposed to the computed value).
> 
> v1 -- The current driver assumes the downstream devices can
>       provide CLKREQ# for ASPM.  These commits accomodate devices
>       w/ or w/o clkreq# and also handle L1SS-capable devices.
> 
>    -- The Raspian Linux folks have already been using a PCIe RC
>       property "brcm,enable-l1ss".  These commits use the same
>       property, in a backward-compatible manner, and the implementaion
>       adds more detail and also automatically identifies devices w/o
>       a clkreq# signal, i.e. most devices plugged into an RPi CM4
>       IO board.

Applied to controller/broadcom, thank you!

[01/02] dt-bindings: PCI: brcmstb: Add property "brcm,clkreq-mode"
        https://git.kernel.org/pci/pci/c/14b15aeb3628
[02/02] PCI: brcmstb: Configure HW CLKREQ# mode appropriate for downstream device
        https://git.kernel.org/pci/pci/c/e2596dcf1e9d

	Krzysztof