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Commit e4e7d597 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Bjorn Helgaas
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PCI/MSI: Update MSI/MSI-X bits in PCIEBUS-HOWTO 



Update the MSI/MSI-X bits in PCIEBUS-HOWTO.  Stop talking about low-level
details that mention deprecated APIs and concentrate on what service
drivers should do and why.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
parent c3cf2c61

Documentation/PCI/PCIEBUS-HOWTO.txt

+7 −26
Original line number Diff line number Diff line
@@ -161,21 +161,13 @@ Since all service drivers of a PCI-PCI Bridge Port device are 
allowed to run simultaneously, below lists a few of possible resource

conflicts with proposed solutions.



6.1 MSI Vector Resource



The MSI capability structure enables a device software driver to call

pci_enable_msi to request MSI based interrupts. Once MSI interrupts

are enabled on a device, it stays in this mode until a device driver

calls pci_disable_msi to disable MSI interrupts and revert back to

INTx emulation mode. Since service drivers of the same PCI-PCI Bridge

port share the same physical device, if an individual service driver

calls pci_enable_msi/pci_disable_msi it may result unpredictable

behavior. For example, two service drivers run simultaneously on the

same physical Root Port. Both service drivers call pci_enable_msi to

request MSI based interrupts. A service driver may not know whether

any other service drivers have run on this Root Port. If either one

of them calls pci_disable_msi, it puts the other service driver

in a wrong interrupt mode.

6.1 MSI and MSI-X Vector Resource



Once MSI or MSI-X interrupts are enabled on a device, it stays in this

mode until they are disabled again.  Since service drivers of the same

PCI-PCI Bridge port share the same physical device, if an individual

service driver enables or disables MSI/MSI-X mode it may result

unpredictable behavior.



To avoid this situation all service drivers are not permitted to

switch interrupt mode on its device. The PCI Express Port Bus driver
@@ -187,17 +179,6 @@ driver. Service drivers should use (struct pcie_device*)dev->irq to 
call request_irq/free_irq. In addition, the interrupt mode is stored

in the field interrupt_mode of struct pcie_device.



6.2 MSI-X Vector Resources



Similar to the MSI a device driver for an MSI-X capable device can

call pci_enable_msix to request MSI-X interrupts. All service drivers

are not permitted to switch interrupt mode on its device. The PCI

Express Port Bus driver is responsible for determining the interrupt

mode and this should be transparent to service drivers. Any attempt

by service driver to call pci_enable_msix/pci_disable_msix may

result unpredictable behavior. Service drivers should use

(struct pcie_device*)dev->irq and call request_irq/free_irq.



6.3 PCI Memory/IO Mapped Regions



Service drivers for PCI Express Power Management (PME), Advanced