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    SubjectRE: [PATCH] PCI: pcie-rcar: Fix OF node passed to MSI irq domain
    Date
    Hi Marc,

    On 12 November 2015 20:31, Marc Zyngier wrote:
    > Phil Edworthy <phil.edworthy@renesas.com> wrote:
    > > On 11 November 2015 16:38, Marc Zyngier wrote:
    > > > On Tue, 10 Nov 2015 16:52:33 +0100
    > > > Thierry Reding <treding@nvidia.com> wrote:
    > > >
    > > > > On Mon, Nov 09, 2015 at 06:01:49PM +0000, Phil Edworthy wrote:
    > > > > > Hi Thierry,
    > > > > >
    > > > > > On 09 November 2015 17:24, Phil wrote:
    > > > > > > On 09 November 2015 16:11, Thierry wrote:
    > > > > > > > On Mon, Nov 09, 2015 at 03:20:24PM +0000, Phil Edworthy wrote:
    > > > > > > > > cc'ing others (Tegra, Altera, Designware) who may have the same
    > bug
    > > > > > > > >
    > > > > > > > > On 03 November 2015 09:28, Phil Edworthy wrote:
    > > > > > > > > > The OF node passed to irq_domain_add_linear() should be a
    > > > > > > > > > pointer to interrupt controller's device tree node, or NULL,
    > > > > > > > > > but not the PCI controller's node.
    > > > > > > > > >
    > > > > > > > > > This fixes an oops in msi_domain_alloc_irqs() when it tries
    > > > > > > > > > to call msi_check().
    > > > > > > > > >
    > > > > > > > > > Signed-off-by: Phil Edworthy <phil.edworthy@renesas.com>
    > > > > > > > > > ---
    > > > > > > > > > drivers/pci/host/pcie-rcar.c | 2 +-
    > > > > > > > > > 1 file changed, 1 insertion(+), 1 deletion(-)
    > > > > > > > > >
    > > > > > > > > > diff --git a/drivers/pci/host/pcie-rcar.c b/drivers/pci/host/pcie-
    > rcar.c
    > > > > > > > > > index 2377bf0..c6fa562 100644
    > > > > > > > > > --- a/drivers/pci/host/pcie-rcar.c
    > > > > > > > > > +++ b/drivers/pci/host/pcie-rcar.c
    > > > > > > > > > @@ -709,7 +709,7 @@ static int rcar_pcie_enable_msi(struct
    > rcar_pcie
    > > > > > > *pcie)
    > > > > > > > > > msi->chip.setup_irq = rcar_msi_setup_irq;
    > > > > > > > > > msi->chip.teardown_irq = rcar_msi_teardown_irq;
    > > > > > > > > >
    > > > > > > > > > - msi->domain = irq_domain_add_linear(pcie->dev->of_node,
    > > > > > > > > > INT_PCI_MSI_NR,
    > > > > > > > > > + msi->domain = irq_domain_add_linear(NULL,
    > INT_PCI_MSI_NR,
    > > > > > > > > > &msi_domain_ops, &msi-
    > > > >chip);
    > > > > > > > > > if (!msi->domain) {
    > > > > > > > > > dev_err(&pdev->dev, "failed to create IRQ domain\n");
    > > > > > > >
    > > > > > > > On Tegra the PCI controller is in fact the interrupt controller for
    > > > > > > > MSIs. And looking at the code here it seems like the same would apply
    > to
    > > > > > > > RCAR.
    > > > > > > Yes you are correct here.
    > > > > > >
    > > > > > > > I'm also slightly confused as to why this would cause ->msi_check() to
    > > > > > > > fail. The default implementation (msi_domain_ops_check()) doesn't
    > do
    > > > > > > > anything.
    > > > > > > >
    > > > > > > > Also, how is passing in NULL instead of a valid struct device_node *
    > > > > > > > going to prevent an oops? Perhaps this is one of those reference
    > count
    > > > > > > > imbalance bugs that have recently been showing up?
    > > > > > > On arm64 (previously I didn't realise this just affects arm64, not arm),
    > > > > > > the changes in commit f075915ac0b11 ("PCI/MSI: Drop domain field
    > from
    > > > > > > msi_controller") and d8a1cb757550 ("PCI/MSI: Let pci_msi_get_domain
    > use
    > > > > > > struct device::msi_domain") return an uninitialized msi domain that
    > leads
    > > > > > > to the oops. It appears that these changes assume that msi interrupt
    > > > > > > controller is separate from the PCI controller.
    > > > > > More accurately, when CONFIG_GENERIC_MSI_IRQ_DOMAIN is enabled,
    > > > > > pci_msi_get_domain() calls dev_get_msi_domain() and at this point
    > > > > > dev->msi_domain is uninitialized.
    > > > >
    > > > > Marc, any idea what's going on here?
    > > >
    > > > Thanks for putting me in the loop.
    > > >
    > > > No precise idea yet, but the proposed fix definitely looks like the
    > > > wrong one. Actually, not passing a node identifier to any domain
    > > > constructor is pretty much always a mistake when using DT.
    > > >
    > > > Can someone post a stack trace for this issue so that I can have a
    > > > look? I'm currently traveling, so expect a slightly delayed reply...
    > >
    > > Unfortunately, not all the code for this arm64 board is upstream
    > > yet, this code base is off 4.3-rc7.
    >
    > Oh, this is arm64? Well, you're not supposed to use the old
    > msi_controller stuff on arm64 - I really want all arm64 controllers to
    > be converted to generic MSI domains. Please have a look at the xgene
    > code, for example.
    Oh right, I wasn't aware of that. I had hoped that drivers weren't so
    arch specific...


    > But irrespective of that, I share Thierry's skepticism:
    >
    > > systemd-udevd[1315]: undefined instruction: pc=ffffffc03106d41c
    > > Code: ffffffc0 311f9740 ffffffc0 3106d138 (ffffffc0)
    > > Internal error: Oops - undefined instruction: 0 [#1] PREEMPT SMP
    > > Modules linked in: e1000e(+)
    > > CPU: 0 PID: 1315 Comm: systemd-udevd Not tainted 4.3.0-rc7+ #4
    > > Hardware name: Renesas Salvator-X board based on r8a7795 (DT)
    > > task: ffffffc0307af080 ti: ffffffc030ecc000 task.ti: ffffffc030ecc000
    > > PC is at 0xffffffc03106d41c
    >
    > You are clearly jumping to nowhereland, and I doubt this is related to
    > the domain of_node being set. Are you overriding arch_setup_msi_irq one
    > way or another?
    No, I'm not overriding arch_setup_msi_irq at all.

    Since the stack trace doesn't help that much I added some tracing:
    pci_msi_setup_msi_irqs()
    calls pci_msi_get_domain()
    calls dev_get_msi_domain(), gets a non-NULL domain.
    pci_msi_setup_msi_irqs()
    calls pci_msi_domain_alloc_irqs()
    calls msi_domain_alloc_irqs()
    msi_domain_alloc_irqs:273: ops=ffffffc03193a810
    msi_domain_alloc_irqs:274: ops->msi_check=ffffffc031161418
    systemd-udevd[1311]: undefined instruction: pc=ffffffc03116141c
    That looks to me as though msi_check is off pointing to the weeds.

    By passing a NULL domain into irq_domain_add_linear() you get:
    pci_msi_setup_msi_irqs()
    calls pci_msi_get_domain()
    calls dev_get_msi_domain(), gets a NULL domain.
    calls arch_setup_msi_irq()
    All ok then.

    Thanks for your help,
    Phil


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