From: Bjorn Helgaas <helgaas@kernel.org>
To: Jim Quinlan <james.quinlan@broadcom.com>
Cc: 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,
"Conor Dooley" <conor+dt@kernel.org>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@vger.kernel.org>,
"Florian Fainelli" <florian.fainelli@broadcom.com>,
"Jim Quinlan" <jim2101024@gmail.com>,
"Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
"Krzysztof Wilczyński" <kw@linux.com>,
"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE"
<linux-arm-kernel@lists.infradead.org>,
"open list" <linux-kernel@vger.kernel.org>,
"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE"
<linux-rpi-kernel@lists.infradead.org>,
"Lorenzo Pieralisi" <lpieralisi@kernel.org>,
"Rob Herring" <robh@kernel.org>
Subject: Re: [PATCH v9 0/4] PCI: brcmstb: Configure appropriate HW CLKREQ# mode
Date: Mon, 6 May 2024 17:31:49 -0500 [thread overview]
Message-ID: <20240506223149.GA1708699@bhelgaas> (raw)
In-Reply-To: <CA+-6iNynMc7-zZ0No0Y30of+uPiz0mSL9brV3R=UGJNC6ytoxg@mail.gmail.com>
On Tue, Apr 30, 2024 at 05:02:45PM -0400, Jim Quinlan wrote:
> On Wed, Apr 3, 2024 at 5:39 PM Jim Quinlan <james.quinlan@broadcom.com> wrote:
> >
> > v9 -- v8 was setting an internal bus timeout to accomodate large L1 exit
> > latencies. After meeting the PCIe HW team it was revealed that the
> > HW default timeout value was set low for the purposes of HW debugging
> > convenience; for nominal operation it needs to be set to a higher
> > value independent of this submission's purpose. This is now a
> > separate commit.
>
> Bjorn,
>
> Did you have some time to look at this? Do you have any comments or questions?
Sorry, I didn't realize you were waiting on me. I think Krzysztof W.
will ultimately take care of these.
I have some minor comments but overall I'm fine with this.
> > -- With v8, Bjorne asked what was preventing a device from exceeding the
> > time required for the above internal bus timeout. The answer to this
> > is for us to set the endpoints' max latency {no-,}snoop value to
> > something below this internal timeout value. If the endpoint
> > respects this value as it should, it will not send an LTR request
> > with a larger latency value and not put itself in a situation
> > that requires more latency than is possible for the platform.
> >
> > Typically, ACPI or FW sets these max latency values. In most of our
> > systems we do not have this happening so it is up to the RC driver to
> > set these values in the endpoint devices. If the endpoints already
> > have non-zero values that are lower than what we are setting, we let
> > them be, as it is possible ACPI or FW set them and knows something
> > that we do not.
> >
> > -- The "clkreq" commit has only been changed to remove the code that was
> > setting the timeout value, as this code is now its own commit.
> >
> > 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.
> >
> > Jim Quinlan (4):
> > dt-bindings: PCI: brcmstb: Add property "brcm,clkreq-mode"
> > PCI: brcmstb: Set reasonable value for internal bus timeout
> > PCI: brcmstb: Set downstream maximum {no-}snoop LTR values
> > PCI: brcmstb: Configure HW CLKREQ# mode appropriate for downstream
> > device
> >
> > .../bindings/pci/brcm,stb-pcie.yaml | 18 ++
> > drivers/pci/controller/pcie-brcmstb.c | 161 +++++++++++++++++-
> > 2 files changed, 170 insertions(+), 9 deletions(-)
> >
> >
> > base-commit: 9f8413c4a66f2fb776d3dc3c9ed20bf435eb305e
> > --
> > 2.17.1
> >
prev parent reply other threads:[~2024-05-06 22:31 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-03 21:38 [PATCH v9 0/4] PCI: brcmstb: Configure appropriate HW CLKREQ# mode Jim Quinlan
2024-04-03 21:38 ` [PATCH v9 1/4] dt-bindings: PCI: brcmstb: Add property "brcm,clkreq-mode" Jim Quinlan
2024-04-03 21:38 ` [PATCH v9 2/4] PCI: brcmstb: Set reasonable value for internal bus timeout Jim Quinlan
2024-05-06 22:45 ` Bjorn Helgaas
2024-04-03 21:39 ` [PATCH v9 3/4] PCI: brcmstb: Set downstream maximum {no-}snoop LTR values Jim Quinlan
2024-04-04 16:47 ` kernel test robot
2024-04-04 16:48 ` kernel test robot
2024-04-03 21:39 ` [PATCH v9 4/4] PCI: brcmstb: Configure HW CLKREQ# mode appropriate for downstream device Jim Quinlan
2024-05-06 23:20 ` Bjorn Helgaas
2024-05-08 17:55 ` Jim Quinlan
2024-05-08 23:33 ` Bjorn Helgaas
2024-04-04 20:01 ` [PATCH v9 0/4] PCI: brcmstb: Configure appropriate HW CLKREQ# mode Cyril Brulebois
2024-04-30 21:02 ` Jim Quinlan
2024-05-06 22:31 ` Bjorn Helgaas [this message]
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