From: Bjorn Andersson <bjorn.andersson@linaro.org>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
Rob Herring <robh+dt@kernel.org>,
Jingoo Han <jingoohan1@gmail.com>,
Gustavo Pimentel <gustavo.pimentel@synopsys.com>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
Krzysztof Wilczy??ski <kw@linux.com>,
Stanimir Varbanov <svarbanov@mm-sol.com>,
linux-arm-msm@vger.kernel.org, linux-pci@vger.kernel.org,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/2] PCI: dwc: Perform host_init() before registering msi
Date: Tue, 24 Aug 2021 14:23:14 -0700 [thread overview]
Message-ID: <YSVjQgDmatkkCxtn@ripper> (raw)
In-Reply-To: <20210824202925.GA3491441@bjorn-Precision-5520>
On Tue 24 Aug 13:29 PDT 2021, Bjorn Helgaas wrote:
> On Tue, Aug 24, 2021 at 01:15:49PM -0700, Bjorn Andersson wrote:
> > On Tue 24 Aug 12:05 PDT 2021, Bjorn Helgaas wrote:
> >
> > > On Mon, Aug 23, 2021 at 08:49:57AM -0700, Bjorn Andersson wrote:
> > > > On the Qualcomm sc8180x platform the bootloader does something related
> > > > to PCI that leaves a pending "msi" interrupt, which with the current
> > > > ordering often fires before init has a chance to enable the clocks that
> > > > are necessary for the interrupt handler to access the hardware.
> > > >
> > > > Move the host_init() call before the registration of the "msi" interrupt
> > > > handler to ensure the host driver has a chance to enable the clocks.
> > >
> > > Did you audit other drivers for similar issues? If they do, we should
> > > fix them all at once.
> >
> > I only looked at the DesignWware drivers, in an attempt to find any
> > issues the proposed reordering.
> >
> > The set of bugs causes by drivers registering interrupts before critical
> > resources tends to be rather visible and I don't know if there's much
> > value in speculatively "fixing" drivers.
> >
> > E.g. a quick look through the drivers I see a similar pattern in
> > pci-tegra.c, but it's unlikely that they have the similar problem in
> > practice and I have no way to validate that a change to the order would
> > have a positive effect - or any side effects.
> >
> > Or am I misunderstanding your request?
>
> That is exactly my request.
Okay.
> I'm not sure if the potential issue you
> noticed in pci-tegra.c is similar to the one I mentioned here:
>
> https://lore.kernel.org/linux-pci/20210624224040.GA3567297@bjorn-Precision-5520/
>
As I still have the tegra driver open, I share your concern about the
use of potentially uninitialized variables.
The problem I was concerned about was however the same as in my patch
and the rockchip one, that if the tegra hardware isn't clocked the
pm_runtime_get_sync() (which would turn on power and clock) happens
after setting up the msi chain handler...
> but I am actually in favor of speculatively fixing drivers even though
> they're hard to test. Code like this tends to get copied to other
> places, and fixing several drivers sometimes exposes opportunities for
> refactoring and sharing code.
>
Looking through the other cases mentioned in your reply above certainly
gives a feeling that this problem has been inherited from driver to
driver...
I've added a ticket to my backlog to take a deeper look at this.
Regards,
Bjorn
next prev parent reply other threads:[~2021-08-24 21:22 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-23 15:49 [PATCH v2 1/2] PCI: dwc: Perform host_init() before registering msi Bjorn Andersson
2021-08-23 15:49 ` [PATCH v2 2/2] PCI: qcom: Add sc8180x compatible Bjorn Andersson
2021-08-23 17:47 ` Rob Herring
2021-08-23 17:46 ` [PATCH v2 1/2] PCI: dwc: Perform host_init() before registering msi Rob Herring
2021-08-24 19:05 ` Bjorn Helgaas
2021-08-24 20:15 ` Bjorn Andersson
2021-08-24 20:29 ` Bjorn Helgaas
2021-08-24 21:23 ` Bjorn Andersson [this message]
2021-10-08 17:48 ` Lorenzo Pieralisi
2021-10-08 19:08 ` Bjorn Andersson
2021-10-12 12:47 ` Lorenzo Pieralisi
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