Re: PCI IO resource question.

[Bjorn Helgaas <helgaas@kernel.org>]

On Wed, Mar 16, 2016 at 04:13:30PM -0400, Murali Karicheri wrote:
> On 03/16/2016 03:29 PM, Bjorn Helgaas wrote:
> > On Wed, Mar 16, 2016 at 02:08:47PM -0400, Murali Karicheri wrote:
> >> Bjorn,
> >>
> >> Thanks for your quick response! Please see below some clarification
> >> and follow up question.
> >>
> >> On 03/16/2016 12:45 PM, Bjorn Helgaas wrote:
> >> 0x1000]
> >>>
> >>> Obviously if the host bridge doesn't support I/O port space, we will
> >>> be unable to assign space for I/O BARs, so you will see errors like
> >>> this.  
> >>>
> >>> We may be able to improve the message and/or make this less noisy.
> >>> Guenter Roeck looked at a similar issue a while ago, but it's not
> >>> completely trivial:
> >>>
> >>>   http://lkml.kernel.org/r/20150515172836.GA27797@svl-evodev-groeck.juniper.net
> >>>
> >>> The PCI core should check in pci_enable_device() whether all the
> >>> device BARs have been assigned.  If not, it should fail.  But if a
> >>> driver doesn't need I/O space, it can use pci_enable_device_mem() to
> >>> indicate that it only needs the MEM BARs.  That should succeed even if
> >>> the I/O BARs aren't assigned.
> >>>
> >>> Bottom line, if you omit I/O space on your host bridge:
> >>>
> >>>   - You will see annoying "no space for" and "failed to assign" messages
> >>>   - Drivers that don't need I/O ports should still work
> >>>   - It's far better to have the messages than it was to pretend that
> >>>     the host bridge supported I/O space when it really didn't.
> >>>
> >>>> [    0.448813] pci 0000:01:00.0: BAR 6: assigned [mem 0x60100000-0x6010ffff pref]
> >>>> [    0.448822] pci 0000:01:00.0: BAR 5: assigned [mem 0x60000000-0x600001ff]
> >>>> [    0.448834] pci 0000:01:00.0: BAR 4: no space for [io  size 0x0010]
> >>>> [    0.448841] pci 0000:01:00.0: BAR 4: failed to assign [io  size 0x0010]
> >>>> [    0.448848] pci 0000:01:00.0: BAR 0: no space for [io  size 0x0008]
> >>>> [    0.448855] pci 0000:01:00.0: BAR 0: failed to assign [io  size 0x0008]
> >>>> [    0.448863] pci 0000:01:00.0: BAR 2: no space for [io  size 0x0008]
> >>>> [    0.448870] pci 0000:01:00.0: BAR 2: failed to assign [io  size 0x0008]
> >>>> [    0.448877] pci 0000:01:00.0: BAR 1: no space for [io  size 0x0004]
> >>>> [    0.448884] pci 0000:01:00.0: BAR 1: failed to assign [io  size 0x0004]
> >>>> [    0.448891] pci 0000:01:00.0: BAR 3: no space for [io  size 0x0004]
> >>>> [    0.448898] pci 0000:01:00.0: BAR 3: failed to assign [io  size 0x0004]
> >>>> [    0.448907] pci 0000:00:00.0: PCI bridge to [bus 01]
> >>>>
> >>>>
> >>>> The original log is below and even with the error, I am able to have SATA
> >>>> drive function as expected over this PCIe interface.
> >>>>
> >>>>
> >>>> [    0.420648] PCI host bridge /soc/pcie@21020000 ranges:
> >>>> [    0.420659]   No bus range found for /soc/pcie@21020000, using [bus 00-ff]
> >>>> [    0.420679]    IO 0x23260000..0x400023263fff -> 0x00000000
> >>>> [    0.420685] Requested IO range too big, new size set to 64K
> >>>> [    0.420702]   MEM 0x60000000..0x6fffffff -> 0x60000000
> >>>> [    0.420713] keystone-pcie 21021000.pcie: error -22: failed to map resource [io  0x0000-0x400000003fff]
> >>>> [    0.431849] keystone-pcie 21021000.pcie: PCI host bridge to bus 0000:00
> >>>> [    0.431861] pci_bus 0000:00: root bus resource [bus 00-ff]
> >>>> [    0.431870] pci_bus 0000:00: root bus resource [io  0x0000-0x400000003fff]
> >>>
> >>> This range is obviously bogus, since it's way too big and not a nice
> >>> round size.  I guess this is what you're fixing.
> >>
> >> Yes. But from your response, I gather it is better to remove the bogus range.
> >> I removed the range, and did a read/write test to the hard drive connected 
> >> to the Marvel SATA that is hooked to the PCIe interface and it still work
> >> without issues. 
> > 
> > If your bridge doesn't support I/O space, you should definitely remove
> > the range.
> > 
> Ok. Will do.
> 
> > I'm curious about this Marvell SATA device, though.  It is this
> > device?
> > 
> 
> Yes.
> 
> >   pci 0000:01:00.0: [1b4b:9182] type 00 class 0x010601
> >   pci 0000:01:00.0: reg 0x10: [io  0x8000-0x8007] 
> >   pci 0000:01:00.0: reg 0x14: [io  0x8040-0x8043] 
> >   pci 0000:01:00.0: reg 0x18: [io  0x8100-0x8107] 
> >   pci 0000:01:00.0: reg 0x1c: [io  0x8140-0x8143] 
> >   pci 0000:01:00.0: reg 0x20: [io  0x800000-0x80000f]
> >   pci 0000:01:00.0: reg 0x24: [mem 0x00900000-0x009001ff]
> >   pci 0000:01:00.0: reg 0x30: [mem 0xd0000000-0xd000ffff pref]
> > 
> > If so, it looks like it uses the drivers/ata/ahci.c driver, which uses
> > pcim_enable_device(), which should require all BARs to be assigned.
> > (It doesn't look like there is a pcim_enable_device_mem() variant.)
> > 
> What does it mean in the context of removing the IO resource DT binding?
> My AHCI SATA driver works fine with the IO DT bindings removed except
> that I see the the error log for assigning IO BAR
> 
> If it expects all resources to be assigned, then it should have 
> failed, right? But not.

Right, I'm expecting the SATA driver to fail when you remove the DT I/O
resource binding.  I want to figure out why it doesn't fail.

> I see following
> 
> [    1.547690] ahci 0000:01:00.0: version 3.0
> [    1.551833] ahci 0000:01:00.0: limiting MRRS to 256
> [    1.556822] ahci 0000:01:00.0: AHCI 0001.0000 32 slots 2 ports 6 Gbps 0x3 impl SATA mode
> [    1.564943] ahci 0000:01:00.0: flags: 64bit ncq sntf led only pmp fbs pio slum part sxs 
> 
> 
> And Then
> 
> [    1.940284] ata1: SATA link down (SStatus 0 SControl 300)
> [    2.140278] ata2: SATA link up 6.0 Gbps (SStatus 133 SControl 300)
> [    2.147029] ata2.00: ATA-9: WDC WD10EZEX-08M2NA0, 01.01A01, max UDMA/100
> [    2.153752] ata2.00: 1953525168 sectors, multi 0: LBA48 NCQ (depth 31/32), AA
> [    2.161524] ata2.00: configured for UDMA/100
> [    2.165957] bounce: isa pool size: 16 pages
> [    2.170289] scsi 1:0:0:0: Direct-Access     ATA      WDC WD10EZEX-08M 1A01 PQ: 0 ANSI: 5
> [    2.178967] sd 1:0:0:0: [sda] 1953525168 512-byte logical blocks: (1.00 TB/932 GiB)
> [    2.186632] sd 1:0:0:0: [sda] 4096-byte physical blocks
> [    2.192047] sd 1:0:0:0: [sda] Write Protect is off
> [    2.196835] sd 1:0:0:0: [sda] Mode Sense: 00 3a 00 00
> [    2.201968] sd 1:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
> [    2.226610]  sda: sda1 sda2
> [    2.230300] sd 1:0:0:0: [sda] Attached SCSI removable disk
> 
> 
> > But if you're on an arm or arm64 platform and you have PCI_PROBE_ONLY
> > set, pcibios_enable_device() doesn't check whether resources are
> > assigned, so the problem would be masked.  We're trying to remove
> > PCI_PROBE_ONLY, or at least remove it from paths like this, so this
> > might become a problem soon.
> > 
> 
> Keystone is ARM v7 A15 based. The driver doesn't set PCI_PROBE_ONLY.
> So am expect face problem when you remove PCI_PROBE_ONLY? I guess not.

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?

> 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?