linux-kernel - Re: [PATCH v2 2/3] PCI: brcmstb: CLKREQ# accomodations of downstream device

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Date:   Fri, 14 Apr 2023 18:19:07 +0200
From:   Cyril Brulebois <kibi@...ian.org>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     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>,
        Phil Elwell <phil@...pberrypi.com>,
        bcm-kernel-feedback-list@...adcom.com, james.quinlan@...adcom.com,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Rob Herring <robh@...nel.org>,
        "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-rpi-kernel@...ts.infradead.org>,
        "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] PCI: brcmstb: CLKREQ# accomodations of downstream
 device

Florian Fainelli <f.fainelli@...il.com> (2023-04-14):
> Cyril, based upon the table and logs you provided whereby you have used the
> following:
> 
> - Raspberry Pi Compute Module 4 (Rev 1.0, 8G RAM, 32G storage)
> - Raspberry Pi Compute Module 4 IO Board
> - SupaHub PCIe-to-multiple-USB adapter, reference PCE6U1C-R02, VER 006S
> 
> in the before/unpatched case we have a PCIe link down and in the
> after/patched we have a PCIe link up but a kernel panic. Neither are great
> nor resulting in a fully functional PCIe device.

Based on Jim's feedback, I'm attaching a new dmesg for the aforementioned
setup, with an unpatched kernel (dmesg-unpatched-pcie-link-up.txt).

I fear that initially I might have not waited enough before power off and
power on when replugging the SupaHub adapter, and I've only seen the PCIe
link down a few times (now that I'm actively paying attention to that
part). I'm indeed seeing PCIe link up consistently (100%) when using the
following method:

    for i in $(seq 1 20); do
      # power on, let the system boot up and settle:
      sispmctl -t 4; sleep 2m
      ssh cm4 sh -c "dmesg > dmesg-$i.txt; poweroff"
      # let the system power down, and power off:
      sleep 30; sispmctl -t 4
      # wait before power cycling:
      sleep 10
    done

> Looking at:
> https://www.amazon.co.uk/SupaHub-Express-BandWidth-Capable-Expanding/dp/B092ZQWG5B
> 
> it would appear that it can accept an external power supply, do you have one
> connected to that USB expansion card by any chance?

With the patched kernel, I have tried several things (leaving the regular
12V adapter plugged in all the time):
 - No external power supply (that's what I've been using in all previous
   attempts).
 - Using a 5V PSU with 2 pins (ground and 5V) plugged on the Ext PSU
   4-pin header on the IO Board.
 - Using a 5V PSU with a SATA connector plugged directly onto the SupaHub
   adapter.

I'm getting the same trace in all cases.

> Are you able to boot the kernel before/after if you disconnect any USB
> peripheral?

The trace is obtained without any USB peripheral (on the extension card or
on the onboard USB slots). Besides the SupaHub adapter on the PCIe slot, I
only have Ethernet and HDMI plugged in (I'm getting traces via serial
console, and operating the system over SSH when it boots fine).

As soon as I unplug the SupaHub board itself, the system boots fine.

> Does that SupaHub board plugged to the CM4 1.0 system work fine in the
> Raspberry Pi kernel tree?

With the Raspberry Pi OS (64-bit) > Raspberry Pi OS Lite image
(2023-02-21-raspios-bullseye-arm64-lite.img.xz), the system at least
boots fine; I haven't tried adding devices to the mix just yet, trying
to stick with that particular setup.

A full dmesg is attached (dmesg-raspios.txt).


Cheers,
-- 
Cyril Brulebois (kibi@...ian.org)            <https://debamax.com/>
D-I release manager -- Release team member -- Freelance Consultant

View attachment "dmesg-unpatched-pcie-link-up.txt" of type "text/plain" (32415 bytes)

View attachment "dmesg-raspios.txt" of type "text/plain" (29206 bytes)

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