linux-kernel - Re: [PATCH v6 0/5] PCI: brcmstb: Configure appropriate HW CLKREQ# mode

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Message-ID: <ZOMhq8a/wnURWsFP@lpieralisi>
Date:   Mon, 21 Aug 2023 10:34:51 +0200
From:   Lorenzo Pieralisi <lpieralisi@...nel.org>
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 <f.fainelli@...il.com>,
        Jim Quinlan <jim2101024@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        "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>,
        Rob Herring <robh@...nel.org>
Subject: Re: [PATCH v6 0/5] PCI: brcmstb: Configure appropriate HW CLKREQ#
 mode

On Fri, Jun 23, 2023 at 10:40:53AM -0400, Jim Quinlan wrote:
> 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.
> 
> 
> Jim Quinlan (5):
>   dt-bindings: PCI: brcmstb: Add brcm,enable-l1ss property
>   PCI: brcmstb: Configure HW CLKREQ# mode appropriate for downstream
>     device

I am not merging the first two patches since the discussion thread
is still open and I'd like to understand better what can/should be
done, sorry.

>   PCI: brcmstb: Set higher value for internal bus timeout
>   PCI: brcmstb: Assert PERST# on BCM2711
>   PCI: brcmstb: Remove stale comment

Is it OK to apply these three on their own ? Overall it would be
great to avoid mixing patches with different end goals in a single
series.

Thanks,
Lorenzo

>  .../bindings/pci/brcm,stb-pcie.yaml           |  9 ++
>  drivers/pci/controller/pcie-brcmstb.c         | 91 ++++++++++++++++---
>  2 files changed, 89 insertions(+), 11 deletions(-)
> 
> 
> base-commit: 8a28a0b6f1a1dcbf5a834600a9acfbe2ba51e5eb
> -- 
> 2.17.1
>