linux-kernel - Re: Why set .suppress_bind_attrs even though .remove() implemented?

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Date:   Fri, 22 Jul 2022 09:38:58 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Johan Hovold <johan@...nel.org>
Cc:     Pali Rohár <pali@...nel.org>,
        Johan Hovold <johan+linaro@...nel.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        Xiaowei Song <songxiaowei@...ilicon.com>,
        Binghui Wang <wangbinghui@...ilicon.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Ryder Lee <ryder.lee@...iatek.com>,
        Jianjun Wang <jianjun.wang@...iatek.com>,
        linux-pci@...r.kernel.org,
        Krzysztof Wilczyński <kw@...ux.com>,
        Ley Foon Tan <ley.foon.tan@...el.com>,
        linux-kernel@...r.kernel.org
Subject: Re: Why set .suppress_bind_attrs even though .remove() implemented?

On Fri, Jul 22, 2022 at 03:26:44PM +0200, Johan Hovold wrote:
> On Thu, Jul 21, 2022 at 05:21:22PM -0500, Bjorn Helgaas wrote:

> > qcom is a DWC driver, so all the IRQ stuff happens in
> > dw_pcie_host_init().  qcom_pcie_remove() does call
> > dw_pcie_host_deinit(), which calls irq_domain_remove(), but nobody
> > calls irq_dispose_mapping().
> > 
> > I'm thoroughly confused by all this.  But I suspect that maybe I
> > should drop the "make qcom modular" patch because it seems susceptible
> > to this problem:
> > 
> >   https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/commit/?h=pci/ctrl/qcom&id=41b68c2d097e
> 
> That should not be necessary.
> 
> As you note above, interrupt handling is implemented in dwc core so if
> there are any issue here at all, which I doubt, then all of the dwc
> drivers that currently can be built as modules would all be broken and
> this would need to be fixed in core.

I don't know yet whether there's an issue.  We need a clear argument
for why there is or is not.  The fact that others might be broken is
not an argument for breaking another one ;)

> I've been using the modular pcie-qcom patch for months now, unloading
> and reloading the driver repeatedly to test power sequencing, without
> noticing any problems whatsoever.

Pali's commit log suggests that unloading the module is not, by
itself, enough to trigger the problem:

  https://lore.kernel.org/linux-pci/20220709161858.15031-1-pali@kernel.org/

Can you test the scenario he mentions?

Bjorn