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

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Message-ID: <YtqllIHY/R/BbR3V@hovoldconsulting.com>
Date:   Fri, 22 Jul 2022 15:26:44 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Bjorn Helgaas <helgaas@...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 Thu, Jul 21, 2022 at 05:21:22PM -0500, Bjorn Helgaas wrote:
> [+to Johan for qcom]
> [-cc Tom, email bounces]
> 
> On Thu, Jul 21, 2022 at 10:46:07PM +0200, Pali Rohár wrote:
> > On Thursday 21 July 2022 14:54:33 Bjorn Helgaas wrote:

> With suppress_bind_attrs, the user can't manually unbind a device, so
> we can't get to mvebu_pcie_remove() that way, but since mvebu is a
> modular driver, I assume we can unload the module and *that* would
> call mvebu_pcie_remove().  Right?

Correct.

> 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'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.

Johan