From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
The ordering of MSI-X enable in hardware is dysfunctional:
1) MSI-X is disabled in the control register
2) Various setup functions
3) pci_msi_setup_msi_irqs() is invoked which ends up accessing
the MSI-X table entries
4) MSI-X is enabled and masked in the control register with the
comment that enabling is required for some hardware to access
the MSI-X table
Step #4 obviously contradicts #3. The history of this is an issue with the
NIU hardware. When #4 was introduced the table access actually happened in
msix_program_entries() which was invoked after enabling and masking MSI-X.
This was changed in commit d71d6432e105 ("PCI/MSI: Kill redundant call of
irq_set_msi_desc() for MSI-X interrupts") which removed the table write
from msix_program_entries().
Interestingly enough nobody noticed and either NIU still works or it did
not get any testing with a kernel 3.19 or later.
Nevertheless this is inconsistent and there is no reason why MSI-X can't be
enabled and masked in the control register early on, i.e. move step #4
above to step #1. This preserves the NIU workaround and has no side effects
on other hardware.
Fixes: d71d6432e105 ("PCI/MSI: Kill redundant call of irq_set_msi_desc() for MSI-X interrupts")
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Ashok Raj <ashok.raj@xxxxxxxxx>
Reviewed-by: Marc Zyngier <maz@xxxxxxxxxx>
Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
---
drivers/pci/msi.c | 28 +++++++++++++++-------------
1 file changed, 15 insertions(+), 13 deletions(-)
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -772,18 +772,25 @@ static int msix_capability_init(struct p
u16 control;
void __iomem *base;
- /* Ensure MSI-X is disabled while it is set up */
- pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_ENABLE, 0);
+ /*
+ * Some devices require MSI-X to be enabled before the MSI-X
+ * registers can be accessed. Mask all the vectors to prevent
+ * interrupts coming in before they're fully set up.
+ */
+ pci_msix_clear_and_set_ctrl(dev, 0, PCI_MSIX_FLAGS_MASKALL |
+ PCI_MSIX_FLAGS_ENABLE);
pci_read_config_word(dev, dev->msix_cap + PCI_MSIX_FLAGS, &control);
/* Request & Map MSI-X table region */
base = msix_map_region(dev, msix_table_size(control));
- if (!base)
- return -ENOMEM;
+ if (!base) {
+ ret = -ENOMEM;
+ goto out_disable;
+ }
ret = msix_setup_entries(dev, base, entries, nvec, affd);
if (ret)
- return ret;
+ goto out_disable;
ret = pci_msi_setup_msi_irqs(dev, nvec, PCI_CAP_ID_MSIX);
if (ret)
@@ -794,14 +801,6 @@ static int msix_capability_init(struct p
if (ret)
goto out_free;
- /*
- * Some devices require MSI-X to be enabled before we can touch the
- * MSI-X registers. We need to mask all the vectors to prevent
- * interrupts coming in before they're fully set up.
- */
- pci_msix_clear_and_set_ctrl(dev, 0,
- PCI_MSIX_FLAGS_MASKALL | PCI_MSIX_FLAGS_ENABLE);
-
msix_program_entries(dev, entries);
ret = populate_msi_sysfs(dev);
@@ -836,6 +835,9 @@ static int msix_capability_init(struct p
out_free:
free_msi_irqs(dev);
+out_disable:
+ pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_ENABLE, 0);
+
return ret;
}
