On Wed, Jun 22, 2016 at 05:43:58PM -0500, Bjorn Helgaas wrote:

On Wed, Jun 08, 2016 at 12:04:50PM +0100, Lorenzo Pieralisi wrote:

quoted

The arm pcibios_enable_device() implementation exists solely
to prevent enabling PCI resources on PCI_PROBE_ONLY systems, since
on those systems the PCI resources are currently not claimed (ie
inserted in the PCI resource tree - which means their parent
pointer is not correctly set-up) therefore they can not be enabled
since this would trigger PCI set-ups failures.

After removing the pci=firmware command line option in:

commit 903589ca7165 ("ARM: 8554/1: kernel: pci: remove pci=firmware
command line parameter handling")

(that was used to set the PCI_PROBE_ONLY flag through the command line)
and by introducing resources claiming in the PCI host controllers
set-ups that have PCI_PROBE_ONLY as a probe option, there is no need for
arch specific pcibios_enable_device() implementations anymore in that
the kernel can rely on the generic pcibios_enable_device()
implementation without resorting to arch specific code to work around
the missing resources claiming enumeration step.

On !PCI_PROBE_ONLY PCI bus set-ups, resources are always assigned
either in pcibios initialization code or PCI host controllers drivers;
since the PCI resource assignment API takes care of inserting the
assigned resources in the resource tree, the resources parent pointers
are correctly set-up, which means that this patch leaves behaviour
unchanged for all arm PCI set-ups that do not set the PCI_PROBE_ONLY
flag.

Remove the pcibios_enable_device() function from the arm arch back-end
so that the kernel now uses its generic implementation.

Signed-off-by: Lorenzo Pieralisi <redacted>
Acked-by: Will Deacon <redacted>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Will Deacon <redacted>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Russell King <redacted>
---
 arch/arm/kernel/bios32.c | 12 ------------
 1 file changed, 12 deletions(-)

diff --git a/arch/arm/kernel/bios32.c b/arch/arm/kernel/bios32.c
index 05e61a2..488545f 100644
--- a/arch/arm/kernel/bios32.c
+++ b/arch/arm/kernel/bios32.c

@@ -590,18 +590,6 @@ resource_size_t pcibios_align_resource(void *data, const struct resource *res,
 	return start;
 }
 
-/**
- * pcibios_enable_device - Enable I/O and memory.
- * @dev: PCI device to be enabled
- */
-int pcibios_enable_device(struct pci_dev *dev, int mask)
-{
-	if (pci_has_flag(PCI_PROBE_ONLY))
-		return 0;
-
-	return pci_enable_resources(dev, mask);
-}

This looks great.

What about the PCI_PROBE_ONLY test in pci_common_init_dev()?  Don't we
need to either remove that test (if it's impossible to get there with
PCI_PROBE_ONLY set), or add a pci_bus_claim_resources() call as we did
in pci_host_common_probe()?

Yes, you are right, I went for the second option given what you
say below and sent you and Russell an additional patch that
should be added to this series.

I think it's unlikely that we'd get to pci_common_init_dev() with
PCI_PROBE_ONLY set:

  - the only way to set PCI_PROBE_ONLY on ARM is to call
    of_pci_check_probe_only(),

  - the only ARM caller of of_pci_check_probe_only() is
    pci_host_common_probe(),

  - pci_host_common_probe() doesn't call pci_common_init_dev().

But I guess it's possible to imagine a platform with both a generic
PCI bridge and a MVEBU, R-Car, or Tegra bridge.  Then
pci_host_common_probe() could set PCI_PROBE_ONLY, and we'd claim
resources under the generic bridge via the previous patch, but still
not claim those under the MVEBU bridge.  Then enabling the MVEBU
devices would fail.

I know this is a ridiculous scenario, but the code looks inconsistent
as it is.

Well, I do not think that's an *existing* scenario, but this does
not mean that the code is correct, so you are right and it has to
be fixed, please let me know if the patch I sent is fine.

I really have to remove PCI_PROBE_ONLY entirely from ARM/ARM64
kernels.

Thanks !
Lorenzo

quoted

 int pci_mmap_page_range(struct pci_dev *dev, struct vm_area_struct *vma,
 			enum pci_mmap_state mmap_state, int write_combine)
 {
-- 
2.6.4


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