linux-kernel - Re: [PATCH v5 2/3] PCI: qcom: Restrict pci transactions after pci suspend

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Date:   Wed, 24 Aug 2022 12:20:17 -0500
From:   Stephen Boyd <swboyd@...omium.org>
To:     Krishna Chaitanya Chundru <quic_krichai@...cinc.com>,
        helgaas@...nel.org
Cc:     linux-pci@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, mka@...omium.org,
        quic_vbadigan@...cinc.com, quic_hemantk@...cinc.com,
        quic_nitegupt@...cinc.com, quic_skananth@...cinc.com,
        quic_ramkri@...cinc.com, manivannan.sadhasivam@...aro.org,
        dmitry.baryshkov@...aro.org, Jingoo Han <jingoohan1@...il.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Stanimir Varbanov <svarbanov@...sol.com>
Subject: Re: [PATCH v5 2/3] PCI: qcom: Restrict pci transactions after pci suspend

Quoting Krishna Chaitanya Chundru (2022-08-23 20:37:59)
>
> On 8/9/2022 12:42 AM, Stephen Boyd wrote:
> > Quoting Krishna chaitanya chundru (2022-08-03 04:28:53)
> >> If the endpoint device state is D0 and irq's are not freed, then
> >> kernel try to mask interrupts in system suspend path by writing
> >> in to the vector table (for MSIX interrupts) and config space (for MSI's).
> >>
> >> These transactions are initiated in the pm suspend after pcie clocks got
> >> disabled as part of platform driver pm  suspend call. Due to it, these
> >> transactions are resulting in un-clocked access and eventually to crashes.
> > Why are the platform driver pm suspend calls disabling clks that early?
> > Can they disable clks in noirq phase, or even later, so that we don't
> > have to check if the device is clocking in the irq poking functions?
> > It's best to keep irq operations fast, so that irq control is fast given
> > that these functions are called from irq flow handlers.
>
> We are registering the pcie pm suspend ops as noirq ops only. And this
> msix and config
>
> access is coming at the later point of time that is reason we added that
> check.
>

What is accessing msix and config? Can you dump_stack() after noirq ops
are called and figure out what is trying to access the bus when it is
powered down?