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SubjectRe: alpha runtime warnings due to commit 0e4c2eeb758 ("alpha/PCI: Replace pci_fixup_irqs() call with host ...")
[+cc linux-pci, linux-ide, DaveM]

On Wed, Sep 27, 2017 at 11:30:34AM +0100, Lorenzo Pieralisi wrote:
> Bjorn, Guenter,
>
> On Wed, Sep 20, 2017 at 12:31:04PM +0100, Lorenzo Pieralisi wrote:
> > On Tue, Sep 19, 2017 at 11:02:33AM -0700, Guenter Roeck wrote:
> > > On Tue, Sep 19, 2017 at 10:12:32AM +0100, Lorenzo Pieralisi wrote:
> > > > On Mon, Sep 18, 2017 at 07:00:55PM -0700, Guenter Roeck wrote:
> > > > > Hi,
> > > > >
> > > > > I see the following runtime warnings in mainline when running alpha images in qemu.
> > > > >
> > > > >
> > > > > Floppy drive(s): fd0 is 2.88M
> > > > > ide0: disabled, no IRQ
> > > > > ide0: failed to initialize IDE interface
> > > > > ide0: disabling port
> > > > > cmd64x 0000:00:02.0: IDE controller (0x1095:0x0646 rev 0x07)
> > > > > CMD64x_IDE 0000:00:02.0: BAR 0: can't reserve [io 0x8050-0x8057]
> > > > > cmd64x 0000:00:02.0: can't reserve resources
> > > > > CMD64x_IDE: probe of 0000:00:02.0 failed with error -16
> > > > > ide_generic: please use "probe_mask=0x3f" module parameter for probing all legacy ISA IDE ports
> > > > > ------------[ cut here ]------------
> > > > > WARNING: CPU: 0 PID: 1 at fs/sysfs/dir.c:31 sysfs_warn_dup+0x94/0xd0
> > > > > sysfs: cannot create duplicate filename '/class/ide_port/ide0'
> > > > > ...
> > > > >
> > > > > Trace:
> > > > > [<fffffc00003308a0>] __warn+0x160/0x190
> > > > > [<fffffc000048c9f4>] sysfs_warn_dup+0x94/0xd0
> > > > > [<fffffc0000330928>] warn_slowpath_fmt+0x58/0x70
> > > > > [<fffffc000048c9f4>] sysfs_warn_dup+0x94/0xd0
> > > > > [<fffffc0000486d40>] kernfs_path_from_node+0x30/0x60
> > > > > [<fffffc00004874ac>] kernfs_put+0x16c/0x2c0
> > > > > [<fffffc00004874ac>] kernfs_put+0x16c/0x2c0
> > > > > [<fffffc000048d010>] sysfs_do_create_link_sd.isra.2+0x100/0x120
> > > > > [<fffffc00005b9d64>] device_add+0x2a4/0x7c0
> > > > > [<fffffc00005ba5cc>] device_create_groups_vargs+0x14c/0x170
> > > > > [<fffffc00005ba518>] device_create_groups_vargs+0x98/0x170
> > > > > [<fffffc00005ba690>] device_create+0x50/0x70
> > > > > [<fffffc00005df36c>] ide_host_register+0x48c/0xa00
> > > > > [<fffffc00005df330>] ide_host_register+0x450/0xa00
> > > > > [<fffffc00005ba2a0>] device_register+0x20/0x50
> > > > > [<fffffc00005df330>] ide_host_register+0x450/0xa00
> > > > > [<fffffc00005df944>] ide_host_add+0x64/0xe0
> > > > > [<fffffc000079b41c>] kobject_uevent_env+0x16c/0x710
> > > > > [<fffffc0000310288>] do_one_initcall+0x68/0x260
> > > > > [<fffffc00007b13bc>] kernel_init+0x1c/0x1a0
> > > > > [<fffffc00007b13a0>] kernel_init+0x0/0x1a0
> > > > > [<fffffc0000311868>] ret_from_kernel_thread+0x18/0x20
> > > > > [<fffffc00007b13a0>] kernel_init+0x0/0x1a0
> > > > >
> > > > > ---[ end trace 24a70433c3e4d374 ]---
> > > > > ide0: disabling port
> > > > >
> > > > > [ multiple times ]
> > > > >
> > > > > A complete log is available at http://kerneltests.org/builders/qemu-alpha-master.
> > > > >
> > > > > Prior to the offending commit, the kernel log looks as follows.
> > > > >
> > > > > ...
> > > > > Uniform Multi-Platform E-IDE driver
> > > > > cmd64x 0000:00:02.0: IDE controller (0x1095:0x0646 rev 0x07)
> > > > > cmd64x 0000:00:02.0: IDE port disabled
> > > > > cmd64x 0000:00:02.0: 100% native mode on irq 28
> > > > > PCI: Setting latency timer of device 0000:00:02.0 to 64
> > > > > ide0: BM-DMA at 0x8040-0x8047
> > > > > Floppy drive(s): fd0 is 2.88M
> > > > > ide0 at 0x8050-0x8057,0x8062 on irq 28 (serialized)
> > > > > ide_generic: please use "probe_mask=0x3f" module parameter for probing all legacy ISA IDE ports
> > > > > ide1 at 0x1f0-0x1f7,0x3f6 on irq 14
> > > > > ide2 at 0x170-0x177,0x376 on irq 15
> > > > > ide-gd driver 1.18
> > > > > ide-cd driver 5.00
> > > > > ...
> > > > >
> > > > > Reverting the commit is not possible due to context changes.
> > > > >
> > > > > Bisect log is attached.
> > > >
> > > > Ok thanks. Can you please check if the diff below fixes the issue ?
> > > >
> > > It does. Feel free to add
> > >
> > > Tested-by: Guenter Roeck <linux@roeck-us.net>
> > >
> > > to the actual patch.
> > >
> > > > I think the problem is that now we allocate the IRQ at device_probe
> > > > instead of device_add time, if the patch below fixes the issue the
> > > > question is whether we want to move pci_assign_irq() to pci_device_add()
> > > > for ALL PCI devices or just fix this for IDE subsytem.
> > > >
> > >
> > > That I can not answer ...
> >
> > It is not a clean-cut answer. Moving pci_assign_irq() from
> >
> > pci_device_probe()
> >
> > to
> >
> > pci_device_add()
> >
> > would fix this issue too and just map/swizzle() irqs for ALL PCI devices
> > earlier (even ones that are not even probed); it should have no side
> > effects (famous last words) and would be a cleaner fix.

Hmmm, this is ugly. I *think* this is related to ide_pci_init_two().
We already call pci_assign_irq() from pci_device_probe(), where we try
to bind one device to a driver. But ide_pci_init_two() deals with
*two* devices: the one pci_device_probe() is trying to bind, and
another random one found via pci_get_slot(). We have not called
pci_assign_irq() for this second device.

That breaks the model the PCI core expects, where we call the driver
probe method for device X, and that method deals only with device X.

We can fix this by doing the pci_assign_irq() either in the PCI core's
device add path or in the driver's probe path (ide_pci_init_two(), as
in the patch below). Doing it in the PCI core is sort of ugly because
there's no obvious reason why we should map/swizzle the IRQ if there's
no driver.

Doing it in the driver is also sort of ugly because this is something
that should be confined to the core (pci_assign_irq() probably should
be declared in drivers/pci/pci.h so it's not available outside the
core).

I think the patch below means we call pci_assign_irq() *twice* on the
device we're binding: once from pci_device_probe() and again from
do_ide_setup_pci_device(). And I guess we might call it twice for the
second device, too: once from do_ide_setup_pci_device() and again if
pci_device_probe() tries to bind it. It's probably idempotent, but it
does seem a little ugly.

I guess I agree that calling pci_assign_irq() from pci_device_add() is
the lesser evil. That will do it unnecessarily in cases where a
device doesn't have a driver, but it should be safe. It sets
pdev->irq but probably doesn't touch the device itself.

We do more IRQ setup at pci_enable_device()-time (or probe-time for
arm64) via acpi_pci_irq_enable(). This also updates pdev->irq. I'd
rather not do that part at device add-time, because it does things
like allocate and enable interrupt links, and we shouldn't do that
until we know we have a driver for the device.

But this is potentially another problem for this "second-device" thing
IDE does. We've called pci_assign_irq() but not acpi_pci_irq_enable()
for the second device, so we may still get the wrong IRQ for it.

> > Fix below is fine but I am not a big fan of it, I would like to
> > get Bjorn's opinion before I send a fix out.
>
> I think that for now the fix below should be ok, I would like to
> send it out before -rc3, the only question is related to the
> "Fixes:" tag, I am reluctant to add:
>
> Fixes: 0e4c2eeb758 ("alpha/PCI: Replace pci_fixup_irqs() call with host bridge mapping hooks")
>
> since this is not necessarily just an alpha/PCI bug (ie it is related to
> IDE legacy IRQ routing - which Guenter hit on Alpha), the tag can be
> misleading in that sense.
>
> Please let me know what you think, I will send out the patch then.
>
> Thanks,
> Lorenzo
>
> > Thanks,
> > Lorenzo
> >
> > > Guenter
> > >
> > > > Lorenzo
> > > >
> > > > -- >8 --
> > > > diff --git a/drivers/ide/setup-pci.c b/drivers/ide/setup-pci.c
> > > > index 112d2fe..94ca9cc 100644
> > > > --- a/drivers/ide/setup-pci.c
> > > > +++ b/drivers/ide/setup-pci.c
> > > > @@ -502,6 +502,8 @@ static int do_ide_setup_pci_device(struct pci_dev *dev,
> > > > {
> > > > int pciirq, ret;
> > > >
> > > > + pci_assign_irq(dev);
> > > > +
> > > > /*
> > > > * Can we trust the reported IRQ?
> > > > */

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