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

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Date:   Thu, 13 Apr 2023 22:06:46 +0200
From:   Cyril Brulebois <kibi@...ian.org>
To:     Jim Quinlan <jim2101024@...il.com>
Cc:     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,
        Florian Fainelli <f.fainelli@...il.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

Hi Jim,

Jim Quinlan <jim2101024@...il.com> (2023-04-13):
> Can you provide (a) the full boot log prior to applying the patch
> series and (b) full boot log after applying the series, using an
> IDENTICAL setup. If it fails on both then it has little to do with my
> patch series.

Just to be clear, the issue I reported was with:
 - Raspberry Pi Compute Module 4 (Rev 1.1, 4G RAM, 32G storage)
 - Raspberry Pi Compute Module 4 IO Board
 - SupaHub PCIe-to-multiple-USB adapter, reference PCE6U1C-R02, VER 006S

This was my minimal reproducer for the kernel panic at boot-up, which
goes away with either v1 or v2. When I realized I didn't actually check
whether the SupaHub board was working correctly, I plugged 2 devices to
obtain this setup:
 - Raspberry Pi Compute Module 4 (Rev 1.1, 4G RAM, 32G storage)
 - Raspberry Pi Compute Module 4 IO Board
 - SupaHub PCIe-to-multiple-USB adapter, reference PCE6U1C-R02, VER 006S
 - Kingston DataTraveler G4 32GB on USB-A port #1 of the SupaHub board.
 - Logitech K120 keyboard on USB-A port #2 of the SupaHub board.

It turns out that this particular revision of the SupaHub board isn't
supported by xhci_hcd directly (failing to probe with error -110) and
one needs to enable CONFIG_USB_XHCI_PCI_RENESAS=m and also ship its
accompanying firmware (/lib/firmware/renesas_usb_fw.mem). With this
updated kernel config, I'm able to use the keyboard and to read data
from the memory stick without problems (70 MB/s).

> In my last series your testing somehow conflated the effect of an
> unrelated MMC interrupt issue so please be precise.

I wish things would be simpler and didn't involve combinatorics, let
alone other bugs/regressions at times, but I'm really trying my best to
navigate and report issues and test patches when I can spare some time…


In my defence, the very similar board PCE6U1C-R02, VER 006 boots without
a kernel panic, and works fine with xhci_hcd without that extra module
and its firmware. It's based on the exact same chip (Renesas Technology
Corp. uPD720201) though, that's why I didn't realize the need for an
extra module until now for the PCE6U1C-R02, VER 006S one. (Florian,
thanks for mentioning .config earlier…)

To sum up, it seems both (sub)versions of that SupaHub PCE6U1C-R02 board
are usable with this patch series: the kernel panic at boot-up is gone,
and USB devices plugged into those boards are working as expected.


But, speaking of combinatorics, while the patch series helps fix
https://bugzilla.kernel.org/show_bug.cgi?id=217276 on that particular
initial combination of CM4 and SupaHub PCE6U1C-R02, VER 006S, it also
generates a regression if I use a different CM4…

Setup:
 - 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

You'll find attached (a) and (b) as requested above, for this setup, as
well as the kernel configuration file:
 - (a) = dmesg-unpatched.txt = boots fine (and USB devices work fine if
   memory sticks or keyboards are plugged in).
 - (b) = dmesg-patched.txt = kernel panic.
 - cm4+pcie.config

I'm getting similar results with the other SupaHub board:
 - 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 006


This is probably best summarized this way:

                              | unpatched    | patched
------------------------------+--------------+--------------
CM4 Rev 1.1 4G/32G + VER 006  | OK           | OK
CM4 Rev 1.1 4G/32G + VER 006S | Kernel panic | OK            ← Bugzilla entry
CM4 Rev 1.0 8G/32G + VER 006  | OK           | Kernel panic
CM4 Rev 1.0 8G/32G + VER 006S | OK           | Kernel panic


(And I'm of course using the same settings regarding the serial console,
to get traces when needed.)


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

View attachment "dmesg-unpatched.txt" of type "text/plain" (30727 bytes)

View attachment "dmesg-patched.txt" of type "text/plain" (15943 bytes)

View attachment "cm4+pcie.config" of type "text/plain" (290287 bytes)

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