Author: Michael Ellerman <[EMAIL PROTECTED]>
AuthorDate: Thu Sep 20 12:48:23 2007 +1000
Committer: Greg Kroah-Hartman <[EMAIL PROTECTED]>
CommitDate: Fri Oct 12 15:03:16 2007 -0700
PCI: Remove no longer correct documentation regarding MSI vector assignment
The MSI vector reservation system described in Documentation/MSI-HOWTO.txt
was removed by Eric in 92db6d10bc1bc43330a4c540fa5b64c83d9d865f. Remove
the references to it in the documentation.
While we're here § 5.5.1 refers to x86 hardware requirements, so make that
Signed-off-by: Michael Ellerman <[EMAIL PROTECTED]>
Cc: Eric W. Biederman <[EMAIL PROTECTED]>
Signed-off-by: Greg Kroah-Hartman <[EMAIL PROTECTED]>
Documentation/MSI-HOWTO.txt | 69 ++----------------------------------------
1 files changed, 4 insertions(+), 65 deletions(-)
diff --git a/Documentation/MSI-HOWTO.txt b/Documentation/MSI-HOWTO.txt
index 0d82407..a51f693 100644
@@ -241,68 +241,7 @@ address space of the MSI-X table/MSI-X PBA. Otherwise, the
will fail enabling MSI-X on its hardware device when it calls the function
-5.3.2 Handling MSI-X allocation
-Determining the number of MSI-X vectors allocated to a function is
-dependent on the number of MSI capable devices and MSI-X capable
-devices populated in the system. The policy of allocating MSI-X
-vectors to a function is defined as the following:
-#of MSI-X vectors allocated to a function = (x - y)/z where
-x = The number of available PCI vector resources by the time
- the device driver calls pci_enable_msix(). The PCI vector
- resources is the sum of the number of unassigned vectors
- (new) and the number of released vectors when any MSI/MSI-X
- device driver switches its hardware device back to a legacy
- mode or is hot-removed. The number of unassigned vectors
- may exclude some vectors reserved, as defined in parameter
- NR_HP_RESERVED_VECTORS, for the case where the system is
- capable of supporting hot-add/hot-remove operations. Users
- may change the value defined in NR_HR_RESERVED_VECTORS to
- meet their specific needs.
-y = The number of MSI capable devices populated in the system.
- This policy ensures that each MSI capable device has its
- vector reserved to avoid the case where some MSI-X capable
- drivers may attempt to claim all available vector resources.
-z = The number of MSI-X capable devices populated in the system.
- This policy ensures that maximum (x - y) is distributed
- evenly among MSI-X capable devices.
-Note that the PCI subsystem scans y and z during a bus enumeration.
-When the PCI subsystem completes configuring MSI/MSI-X capability
-structure of a device as requested by its device driver, y/z is
-5.3.3 Handling MSI-X shortages
-For the case where fewer MSI-X vectors are allocated to a function
-than requested, the function pci_enable_msix() will return the
-maximum number of MSI-X vectors available to the caller. A device
-driver may re-send its request with fewer or equal vectors indicated
-in the return. For example, if a device driver requests 5 vectors, but
-the number of available vectors is 3 vectors, a value of 3 will be
-returned as a result of pci_enable_msix() call. A function could be
-designed for its driver to use only 3 MSI-X table entries as
-different combinations as ABC--, A-B-C, A--CB, etc. Note that this
-patch does not support multiple entries with the same vector. Such
-attempt by a device driver to use 5 MSI-X table entries with 3 vectors
-as ABBCC, AABCC, BCCBA, etc will result as a failure by the function
-pci_enable_msix(). Below are the reasons why supporting multiple
-entries with the same vector is an undesirable solution.
- - The PCI subsystem cannot determine the entry that
- generated the message to mask/unmask MSI while handling
- software driver ISR. Attempting to walk through all MSI-X
- table entries (2048 max) to mask/unmask any match vector
- is an undesirable solution.
- - Walking through all MSI-X table entries (2048 max) to handle
- SMP affinity of any match vector is an undesirable solution.
-5.3.4 API pci_enable_msix
+5.3.2 API pci_enable_msix
int pci_enable_msix(struct pci_dev *dev, struct msix_entry *entries, int nvec)
@@ -339,7 +278,7 @@ a failure. This failure may be a result of duplicate entries
specified in second argument, or a result of no available vector,
or a result of failing to initialize MSI-X table entries.
-5.3.5 API pci_disable_msix
+5.3.3 API pci_disable_msix
void pci_disable_msix(struct pci_dev *dev)
@@ -349,7 +288,7 @@ always call free_irq() on all MSI-X vectors it has done
on before calling this API. Failure to do so results in a BUG_ON() and
a device will be left with MSI-X enabled and leaks its vectors.
-5.3.6 MSI-X mode vs. legacy mode diagram
+5.3.4 MSI-X mode vs. legacy mode diagram
The below diagram shows the events which switch the interrupt
mode on the MSI-X capable device function between MSI-X mode and
@@ -407,7 +346,7 @@ between MSI mod MSI-X mode during a run-time.
MSI/MSI-X support requires support from both system hardware and
individual hardware device functions.
-5.5.1 System hardware support
+5.5.1 Required x86 hardware support
Since the target of MSI address is the local APIC CPU, enabling
MSI/MSI-X support in the Linux kernel is dependent on whether existing
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