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authorLinus Torvalds <torvalds@linux-foundation.org>2014-02-20 12:46:24 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2014-02-20 12:46:24 -0800
commitd158fc7f36a25e19791d25a55da5623399a2644f (patch)
tree97549c3779a50a1abfc69f6d1a4f4fa2a6dde214 /Documentation
parent54dfffde22ee5ac5a6f912eb451b52683ef3ea7f (diff)
parentfc40363b2140f5777c88e67814fac9327bf1ee68 (diff)
downloadlinux-d158fc7f36a25e19791d25a55da5623399a2644f.tar.gz
Merge tag 'pci-v3.14-fixes-1' of git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci
Pull PCI updates from Bjorn Helgaas: "The most interesting thing here is the change to enable INTx (by clearing PCI_COMMAND_INTX_DISABLE) if the BIOS left INTx disabled. Apparently the Baytrail BIOS does this, which means EHCI doesn't work. Also, fix an AHCI MSI regression and other issues with the recent MSI changes. This also adds pci_enable_msi_exact() and pci_enable_msix_exact(), which aren't regression fixes, but will keep us from touching drivers twice (once to stop using the deprecated pci_enable_msi(), etc., and again to use the *_exact() variants). There's also a minor MVEBU fix. Summary: MSI: - Fix AHCI single-MSI fallback (Alexander Gordeev) - Fix populate_msi_sysfs() error paths (Greg Kroah-Hartman) - Fix htmldocs problem (Masanari Iida) - Add pci_enable_msi_exact() and pci_enable_msix_exact() (Alexander Gordeev) - Update documentation (Alexander Gordeev) Miscellaneous: - mvebu: expose device ID & revision via lspci (Andrew Lunn) - Enable INTx if the BIOS left them disabled (Bjorn Helgaas)" * tag 'pci-v3.14-fixes-1' of git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci: ahci: Fix broken fallback to single MSI mode PCI: Enable INTx if BIOS left them disabled PCI/MSI: Add pci_enable_msi_exact() and pci_enable_msix_exact() PCI/MSI: Fix cut-and-paste errors in documentation PCI/MSI: Add pci_enable_msi() documentation back PCI/MSI: Fix pci_msix_vec_count() htmldocs failure PCI/MSI: Fix leak of msi_attrs PCI/MSI: Check kmalloc() return value, fix leak of name PCI: mvebu: Use Device ID and revision from underlying endpoint
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/PCI/MSI-HOWTO.txt119
1 files changed, 109 insertions, 10 deletions
diff --git a/Documentation/PCI/MSI-HOWTO.txt b/Documentation/PCI/MSI-HOWTO.txt
index a8d01005f480..10a93696e55a 100644
--- a/Documentation/PCI/MSI-HOWTO.txt
+++ b/Documentation/PCI/MSI-HOWTO.txt
@@ -82,7 +82,19 @@ Most of the hard work is done for the driver in the PCI layer. It simply
has to request that the PCI layer set up the MSI capability for this
device.
-4.2.1 pci_enable_msi_range
+4.2.1 pci_enable_msi
+
+int pci_enable_msi(struct pci_dev *dev)
+
+A successful call allocates ONE interrupt to the device, regardless
+of how many MSIs the device supports. The device is switched from
+pin-based interrupt mode to MSI mode. The dev->irq number is changed
+to a new number which represents the message signaled interrupt;
+consequently, this function should be called before the driver calls
+request_irq(), because an MSI is delivered via a vector that is
+different from the vector of a pin-based interrupt.
+
+4.2.2 pci_enable_msi_range
int pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec)
@@ -147,6 +159,11 @@ static int foo_driver_enable_msi(struct pci_dev *pdev, int nvec)
return pci_enable_msi_range(pdev, nvec, nvec);
}
+Note, unlike pci_enable_msi_exact() function, which could be also used to
+enable a particular number of MSI-X interrupts, pci_enable_msi_range()
+returns either a negative errno or 'nvec' (not negative errno or 0 - as
+pci_enable_msi_exact() does).
+
4.2.1.3 Single MSI mode
The most notorious example of the request type described above is
@@ -158,7 +175,27 @@ static int foo_driver_enable_single_msi(struct pci_dev *pdev)
return pci_enable_msi_range(pdev, 1, 1);
}
-4.2.2 pci_disable_msi
+Note, unlike pci_enable_msi() function, which could be also used to
+enable the single MSI mode, pci_enable_msi_range() returns either a
+negative errno or 1 (not negative errno or 0 - as pci_enable_msi()
+does).
+
+4.2.3 pci_enable_msi_exact
+
+int pci_enable_msi_exact(struct pci_dev *dev, int nvec)
+
+This variation on pci_enable_msi_range() call allows a device driver to
+request exactly 'nvec' MSIs.
+
+If this function returns a negative number, it indicates an error and
+the driver should not attempt to request any more MSI interrupts for
+this device.
+
+By contrast with pci_enable_msi_range() function, pci_enable_msi_exact()
+returns zero in case of success, which indicates MSI interrupts have been
+successfully allocated.
+
+4.2.4 pci_disable_msi
void pci_disable_msi(struct pci_dev *dev)
@@ -172,7 +209,7 @@ on any interrupt for which it previously called request_irq().
Failure to do so results in a BUG_ON(), leaving the device with
MSI enabled and thus leaking its vector.
-4.2.3 pci_msi_vec_count
+4.2.4 pci_msi_vec_count
int pci_msi_vec_count(struct pci_dev *dev)
@@ -257,8 +294,8 @@ possible, likely up to the limit returned by pci_msix_vec_count() function:
static int foo_driver_enable_msix(struct foo_adapter *adapter, int nvec)
{
- return pci_enable_msi_range(adapter->pdev, adapter->msix_entries,
- 1, nvec);
+ return pci_enable_msix_range(adapter->pdev, adapter->msix_entries,
+ 1, nvec);
}
Note the value of 'minvec' parameter is 1. As 'minvec' is inclusive,
@@ -269,8 +306,8 @@ In this case the function could look like this:
static int foo_driver_enable_msix(struct foo_adapter *adapter, int nvec)
{
- return pci_enable_msi_range(adapter->pdev, adapter->msix_entries,
- FOO_DRIVER_MINIMUM_NVEC, nvec);
+ return pci_enable_msix_range(adapter->pdev, adapter->msix_entries,
+ FOO_DRIVER_MINIMUM_NVEC, nvec);
}
4.3.1.2 Exact number of MSI-X interrupts
@@ -282,10 +319,15 @@ parameters:
static int foo_driver_enable_msix(struct foo_adapter *adapter, int nvec)
{
- return pci_enable_msi_range(adapter->pdev, adapter->msix_entries,
- nvec, nvec);
+ return pci_enable_msix_range(adapter->pdev, adapter->msix_entries,
+ nvec, nvec);
}
+Note, unlike pci_enable_msix_exact() function, which could be also used to
+enable a particular number of MSI-X interrupts, pci_enable_msix_range()
+returns either a negative errno or 'nvec' (not negative errno or 0 - as
+pci_enable_msix_exact() does).
+
4.3.1.3 Specific requirements to the number of MSI-X interrupts
As noted above, there could be devices that can not operate with just any
@@ -332,7 +374,64 @@ Note how pci_enable_msix_range() return value is analized for a fallback -
any error code other than -ENOSPC indicates a fatal error and should not
be retried.
-4.3.2 pci_disable_msix
+4.3.2 pci_enable_msix_exact
+
+int pci_enable_msix_exact(struct pci_dev *dev,
+ struct msix_entry *entries, int nvec)
+
+This variation on pci_enable_msix_range() call allows a device driver to
+request exactly 'nvec' MSI-Xs.
+
+If this function returns a negative number, it indicates an error and
+the driver should not attempt to allocate any more MSI-X interrupts for
+this device.
+
+By contrast with pci_enable_msix_range() function, pci_enable_msix_exact()
+returns zero in case of success, which indicates MSI-X interrupts have been
+successfully allocated.
+
+Another version of a routine that enables MSI-X mode for a device with
+specific requirements described in chapter 4.3.1.3 might look like this:
+
+/*
+ * Assume 'minvec' and 'maxvec' are non-zero
+ */
+static int foo_driver_enable_msix(struct foo_adapter *adapter,
+ int minvec, int maxvec)
+{
+ int rc;
+
+ minvec = roundup_pow_of_two(minvec);
+ maxvec = rounddown_pow_of_two(maxvec);
+
+ if (minvec > maxvec)
+ return -ERANGE;
+
+retry:
+ rc = pci_enable_msix_exact(adapter->pdev,
+ adapter->msix_entries, maxvec);
+
+ /*
+ * -ENOSPC is the only error code allowed to be analyzed
+ */
+ if (rc == -ENOSPC) {
+ if (maxvec == 1)
+ return -ENOSPC;
+
+ maxvec /= 2;
+
+ if (minvec > maxvec)
+ return -ENOSPC;
+
+ goto retry;
+ } else if (rc < 0) {
+ return rc;
+ }
+
+ return maxvec;
+}
+
+4.3.3 pci_disable_msix
void pci_disable_msix(struct pci_dev *dev)