[PATCH 0/2] Disable MSI/MSI-X interrupts manually at PCI probe time in PowerPC architecture

These 2 patches correct a bogus behaviour introduced by commit 1851617cd2
("PCI/MSI: Disable MSI at enumeration even if kernel doesn't support MSI").
The commit moved the logic responsible to disable MSI/MSI-X interrupts
at PCI probe time to a new function, named pci_msi_setup_pci_dev(), that
is not reachable in the code path of PowerPC pSeries platform.

Since then, devices aren't able to activate MSI/MSI-X capability, even
after boot. The first patch makes the function pci_msi_setup_pci_dev()
non-static. The second patch inserts a call to the function in powerpc
code, so it explicitly disables MSI/MSI-X interrupts at PCI probe time.

Guilherme G. Piccoli (2):
  PCI: Make pci_msi_setup_pci_dev() non-static for use by arch code
  powerpc/PCI: Disable MSI/MSI-X interrupts at PCI probe time in OF case

 arch/powerpc/kernel/pci_of_scan.c | 3 +++
 drivers/pci/probe.c               | 2 +-
 include/linux/pci.h               | 1 +
 3 files changed, 5 insertions(+), 1 deletion(-)

-- 
2.1.0

Commit 1851617cd2 ("PCI/MSI: Disable MSI at enumeration even if kernel
doesn't support MSI") changed the location of the code that disables
MSI/MSI-X interrupts at PCI probe time in devices that have this flag set.
It moved the code from pci_msi_init_pci_dev() to a new function named
pci_msi_setup_pci_dev(), called by pci_setup_device().

Since then, the pSeries platform of the powerpc architecture needs to
disable MSI at PCI probe time manually, as the code flow doesn't
reach pci_setup_device(). For doing so, it wants to call
pci_msi_setup_pci_dev(). This patch makes the required function
non-static, so that it will be called on PCI probe path on powerpc pSeries
platform in next patch.

Signed-off-by: Guilherme G. Piccoli <redacted>
---
 drivers/pci/probe.c | 2 +-
 include/linux/pci.h | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index cefd636..520c5b6 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c

@@ -1103,7 +1103,7 @@ int pci_cfg_space_size(struct pci_dev *dev)
 
 #define LEGACY_IO_RESOURCE	(IORESOURCE_IO | IORESOURCE_PCI_FIXED)
 
-static void pci_msi_setup_pci_dev(struct pci_dev *dev)
+void pci_msi_setup_pci_dev(struct pci_dev *dev)
 {
 	/*
 	 * Disable the MSI hardware to avoid screaming interrupts

diff --git a/include/linux/pci.h b/include/linux/pci.h
index 8a0321a..860c751 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h

@@ -1202,6 +1202,7 @@ struct msix_entry {
 	u16	entry;	/* driver uses to specify entry, OS writes */
 };
 
+void pci_msi_setup_pci_dev(struct pci_dev *dev);
 
 #ifdef CONFIG_PCI_MSI
 int pci_msi_vec_count(struct pci_dev *dev);

-- 
2.1.0

Since the commit 1851617cd2 ("PCI/MSI: Disable MSI at enumeration even if
kernel doesn't support MSI"), MSI/MSI-X interrupts aren't being disabled
at PCI probe time, as the logic responsible for this was moved in the
aforementioned commit from pci_device_add() to pci_setup_device(). The
latter function is not reachable on PowerPC pSeries platform during
Open Firmware PCI probing time.

This patch calls pci_msi_setup_pci_dev() explicitly to disable MSI/MSI-X
during PCI probe time on pSeries platform.

Signed-off-by: Guilherme G. Piccoli <redacted>
---
 arch/powerpc/kernel/pci_of_scan.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/powerpc/kernel/pci_of_scan.c b/arch/powerpc/kernel/pci_of_scan.c
index 42e02a2..0e920f3 100644
--- a/arch/powerpc/kernel/pci_of_scan.c
+++ b/arch/powerpc/kernel/pci_of_scan.c

@@ -191,6 +191,9 @@ struct pci_dev *of_create_pci_dev(struct device_node *node,
 
 	pci_device_add(dev, bus);
 
+	/* Disable MSI/MSI-X here to avoid bogus interrupts */
+	pci_msi_setup_pci_dev(dev);
+
 	return dev;
 }
 EXPORT_SYMBOL(of_create_pci_dev);

-- 
2.1.0

Hi Guilherme,

Thanks for the patches.

On Tue, 2015-08-18 at 18:13 -0300, Guilherme G. Piccoli wrote:

Commit 1851617cd2 ("PCI/MSI: Disable MSI at enumeration even if kernel
doesn't support MSI") changed the location of the code that disables
MSI/MSI-X interrupts at PCI probe time in devices that have this flag set.
It moved the code from pci_msi_init_pci_dev() to a new function named
pci_msi_setup_pci_dev(), called by pci_setup_device().

OK.

Since then, the pSeries platform of the powerpc architecture needs to
disable MSI at PCI probe time manually, as the code flow doesn't
reach pci_setup_device(). 

For doing so, it wants to call
pci_msi_setup_pci_dev(). This patch makes the required function
non-static, so that it will be called on PCI probe path on powerpc pSeries
platform in next patch.

I didn't follow that entirely, I think you mean something like:

  The pseries PCI probing code does not call pci_setup_device(), so since
  commit 1851617cd2 pci_msi_setup_pci_dev() is not called and MSIs are left
  enabled, which is a bug.

  To fix this the pseries PCI probe should manually call
  pci_msi_setup_pci_dev(), so make it non-static.


Does that look OK?

Also you haven't CC'ed the original author of the commit, or the PCI
maintainer, or the relevant lists.

That would be:

    Michael S. Tsirkin [off-list ref]
    Bjorn Helgaas [off-list ref]
    linux-pci@vger.kernel.org
    linux-kernel@vger.kernel.org


And finally both patches should have a fixes line, such as:

Fixes: 1851617cd2da ("PCI/MSI: Disable MSI at enumeration even if kernel doesn't support MSI")

cheers