linux-kernel - Re: [PATCH v1 4/4] PCI: brcmstb: add shutdown call to driver

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Message-ID: <CAL_Jsq++cfNM8sEygMn45Ue8BPPX+8P=ag=bURKvuUuLPvvtUQ@mail.gmail.com>
Date:   Wed, 26 May 2021 11:11:52 -0500
From:   Rob Herring <robh@...nel.org>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Jim Quinlan <jim2101024@...il.com>,
        PCI <linux-pci@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        "maintainer:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <bcm-kernel-feedback-list@...adcom.com>,
        Jim Quinlan <james.quinlan@...adcom.com>,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "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 v1 4/4] PCI: brcmstb: add shutdown call to driver

On Tue, May 25, 2021 at 4:18 PM Bjorn Helgaas <helgaas@...nel.org> wrote:
>
> Capitalize "Add" in the subject.
>
> On Tue, Apr 27, 2021 at 01:51:39PM -0400, Jim Quinlan wrote:
> > The shutdown() call is similar to the remove() call except the former does
> > not need to invoke pci_{stop,remove}_root_bus(), and besides, errors occur
> > if it does.
>
> This doesn't explain why shutdown() is necessary.  "errors occur"
> might be a hint, except that AFAICT, many similar drivers do invoke
> pci_stop_root_bus() and pci_remove_root_bus() (several of them while
> holding pci_lock_rescan_remove()), without implementing .shutdown().
>
> It is ... unfortunate that there's such a variety of implementations
> here.  I don't believe these driver differences are all necessary
> consequences of hardware differences.

What's correct here?

This was on my radar and something we should get in front of. It's
only a matter of time until everyone is converting their drivers to
modules since that is now the Android WayTM. My plan here was to
register a devm hook to call pci_stop_root_bus() and
pci_remove_root_bus(). That way every driver doesn't have to implement
a remove() hook. Though maybe they all need to quiesce themselves
anyways.

Rob