On Fri, Mar 18, 2016 at 11:28:02AM +0000, Lorenzo Pieralisi wrote:
> On Thu, Mar 17, 2016 at 05:28:31PM -0400, Murali Karicheri wrote:
>
> [...]
>
> > > The only ways I see that PCI_PROBE_ONLY can be set on ARM are if you have
> > > "linux,pci-probe-only" in your DT or you boot with "pci=firmware".
> > >
> > > I expect you're in this path:
> > >
> > > ahci_init_one
> > > pcim_enable_device
> > > pci_enable_device
> > > pci_enable_device_flags(dev, IORESOURCE_MEM | IORESOURCE_IO)
> > > # build "bars" mask
> > > do_pci_enable_device(dev, bars)
> > > pcibios_enable_device
> > > if (pci_has_flag(PCI_PROBE_ONLY))
> > > return 0;
> > > pci_enable_resources
> > >
> > > Can you add a little debug code like this to verify that we're in this
> > > path?
> >
> > Yes we are in the path.
> >
> >
> > [ 1.557561] ahci_init_one
> > [ 1.560214] ahci 0000:01:00.0: version 3.0
> > [ 1.564302] pcim_enable_device
> > [ 1.567349] pci_enable_device
> > [ 1.570340] pci_enable_device_flags
> > [ 1.573824] do_pci_enable_device
> > [ 1.577042] pcibios_enable_device
> > [ 1.580380] pci_enable_resources
>
> So resources are actually enabled (ie PCI_PROBE_ONLY is not set)
> and that makes sense otherwise you would not be able to use the
> MEM resources anyway (ie they would not be enabled).
>
> I suspect the PCI dev IO resources were reset in reset_resource() in
> assign_requested_resource_sorted(), hence the bar mask that is built
> in pci_enable_device_flags() does not contain the IO resources,
> it would be helpful if you can print the bar mask passed to
> pcibios_enable_device() (ie the mask parameter).
I didn't look at the code to try to validate this theory, but it seems
plausible, and Murali could easily test it.
The very existence of reset_resource(), which clears res->flags, is a
problem because it means we're losing information about a hardware
BAR. The fact that Linux throws away that information certainly
doesn't keep the device from responding based on the BAR contents.
If we're unable to assign any I/O BARs for a device, and we use
reset_resource() on them, pci_enable_resources() would not find any
IORESOURCE_IO BARs, so it would not turn on PCI_COMMAND_IO, so things
might appear to "work". But pci_enable_resources() never turns
PCI_COMMAND_IO *off*, so if firmware left it enabled, we could still
have an issue.
We definitely have a problem if a device has two I/O BARs and we
assign one but call reset_resource() on the other. Then
pci_enable_resources() won't know about the second one, so it will
turn on PCI_COMMAND_IO. Then we have a potential conflict because the
second BAR is enabled but we don't know its contents.
> Not saying that's what should happen, I think that's what's happening,
> that's the only reason I see why you do not have pci_enable_resources()
> failures when you remove the IO range from the host bridge.
Makes a lot of sense; thanks for looking at this.
> > [ 1.583608] ahci 0000:01:00.0: limiting MRRS to 256
> > [ 1.588595] ahci 0000:01:00.0: AHCI 0001.0000 32 slots 2 ports 6 Gbps 0x3 impl SATA mode
> > [ 1.596716] ahci 0000:01:00.0: flags: 64bit ncq sntf led only pmp fbs pio slum part sxs
> > [ 1.606183] scsi host0: ahci
> > [ 1.609448] scsi host1: ahci
> > [ 1.612636] ata1: SATA max UDMA/133 abar m512@0x60000000 port 0x60000100 irq 82
> > [ 1.619974] ata2: SATA max UDMA/133 abar m512@0x60000000 port 0x60000180 irq 82
> >
> > >
> > >> I looked at pci_enable_resources()
> > >>
> > >> for (i = 0; i < PCI_NUM_RESOURCES; i++) {
> > >> if (!(mask & (1 << i)))
> > >> continue;
> > >>
> > >> r = &dev->resource[i];
> > >
> > > dev_info(&dev->dev, "BAR %d %pR mask %#04x parent %p\n", i, r, mask, r->parent);
> > >
> > >>
> > >> if (!(r->flags & (IORESOURCE_IO | IORESOURCE_MEM)))
> > >> continue;
> > >> if ((i == PCI_ROM_RESOURCE) &&
> > >> (!(r->flags & IORESOURCE_ROM_ENABLE)))
> > >> continue;
> > >>
> > >> if (r->flags & IORESOURCE_UNSET) {
> > >> dev_err(&dev->dev, "can't enable device: BAR %d %pR not assigned\n",
> > >> i, r);
> > >> return -EINVAL;
> > >> }
> > >>
> > >> if (!r->parent) {
> > >> dev_err(&dev->dev, "can't enable device: BAR %d %pR not claimed\n",
> > >> i, r);
> > >> return -EINVAL;
> > >> }
> > >>
> > >> I don't see the error "can't enable device: BAR %d %pR not assigned" , so it doesn't
> > >> depend on IO bar as you mention below or is it in a different function?
> > >
> >
> >
> > --
> > Murali Karicheri
> > Linux Kernel, Keystone
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-pci" in
> > the body of a message to majordomo@xxxxxxxxxxxxxxx
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> >
> --
> To unsubscribe from this list: send the line "unsubscribe linux-pci" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe linux-pci" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
