PCI/MSI: Add pci_enable_msi_range() and pci_enable_msix_range()
This adds pci_enable_msi_range(), which supersedes the pci_enable_msi()
and pci_enable_msi_block() MSI interfaces.
It also adds pci_enable_msix_range(), which supersedes the
pci_enable_msix() MSI-X interface.
The old interfaces have three categories of return values:
negative: failure; caller should not retry
positive: failure; value indicates number of interrupts that *could*
have been allocated, and caller may retry with a smaller request
zero: success; at least as many interrupts allocated as requested
It is error-prone to handle these three cases correctly in drivers.
The new functions return either a negative error code or a number of
successfully allocated MSI/MSI-X interrupts, which is expected to lead to
clearer device driver code.
pci_enable_msi(), pci_enable_msi_block() and pci_enable_msix() still exist
unchanged, but are deprecated and may be removed after callers are updated.
[bhelgaas: tweak changelog]
Suggested-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Alexander Gordeev
Bjorn Helgaas
Родитель
ff1aa430a2
Коммит
302a2523c2
|
|
@ -82,67 +82,97 @@ 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
|
||||
4.2.1 pci_enable_msi_range
|
||||
|
||||
int pci_enable_msi(struct pci_dev *dev)
|
||||
int pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec)
|
||||
|
||||
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.
|
||||
This function allows a device driver to request any number of MSI
|
||||
interrupts within specified range from 'minvec' to 'maxvec'.
|
||||
|
||||
4.2.2 pci_enable_msi_block
|
||||
|
||||
int pci_enable_msi_block(struct pci_dev *dev, int count)
|
||||
|
||||
This variation on the above call allows a device driver to request multiple
|
||||
MSIs. The MSI specification only allows interrupts to be allocated in
|
||||
powers of two, up to a maximum of 2^5 (32).
|
||||
|
||||
If this function returns 0, it has succeeded in allocating at least as many
|
||||
interrupts as the driver requested (it may have allocated more in order
|
||||
to satisfy the power-of-two requirement). In this case, the function
|
||||
enables MSI on this device and updates dev->irq to be the lowest of
|
||||
the new interrupts assigned to it. The other interrupts assigned to
|
||||
the device are in the range dev->irq to dev->irq + count - 1.
|
||||
If this function returns a positive number it indicates the number of
|
||||
MSI interrupts that have been successfully allocated. In this case
|
||||
the device is switched from pin-based interrupt mode to MSI mode and
|
||||
updates dev->irq to be the lowest of the new interrupts assigned to it.
|
||||
The other interrupts assigned to the device are in the range dev->irq
|
||||
to dev->irq + returned value - 1. Device driver can use the returned
|
||||
number of successfully allocated MSI interrupts to further allocate
|
||||
and initialize device resources.
|
||||
|
||||
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. If this function returns a positive number, it is
|
||||
less than 'count' and indicates the number of interrupts that could have
|
||||
been allocated. In neither case is the irq value updated or the device
|
||||
switched into MSI mode.
|
||||
this device.
|
||||
|
||||
The device driver must decide what action to take if
|
||||
pci_enable_msi_block() returns a value less than the number requested.
|
||||
For instance, the driver could still make use of fewer interrupts;
|
||||
in this case the driver should call pci_enable_msi_block()
|
||||
again. Note that it is not guaranteed to succeed, even when the
|
||||
'count' has been reduced to the value returned from a previous call to
|
||||
pci_enable_msi_block(). This is because there are multiple constraints
|
||||
on the number of vectors that can be allocated; pci_enable_msi_block()
|
||||
returns as soon as it finds any constraint that doesn't allow the
|
||||
call to succeed.
|
||||
This function should be called before the driver calls request_irq(),
|
||||
because MSI interrupts are delivered via vectors that are different
|
||||
from the vector of a pin-based interrupt.
|
||||
|
||||
4.2.3 pci_disable_msi
|
||||
It is ideal if drivers can cope with a variable number of MSI interrupts;
|
||||
there are many reasons why the platform may not be able to provide the
|
||||
exact number that a driver asks for.
|
||||
|
||||
There could be devices that can not operate with just any number of MSI
|
||||
interrupts within a range. See chapter 4.3.1.3 to get the idea how to
|
||||
handle such devices for MSI-X - the same logic applies to MSI.
|
||||
|
||||
4.2.1.1 Maximum possible number of MSI interrupts
|
||||
|
||||
The typical usage of MSI interrupts is to allocate as many vectors as
|
||||
possible, likely up to the limit returned by pci_msi_vec_count() function:
|
||||
|
||||
static int foo_driver_enable_msi(struct pci_dev *pdev, int nvec)
|
||||
{
|
||||
return pci_enable_msi_range(pdev, 1, nvec);
|
||||
}
|
||||
|
||||
Note the value of 'minvec' parameter is 1. As 'minvec' is inclusive,
|
||||
the value of 0 would be meaningless and could result in error.
|
||||
|
||||
Some devices have a minimal limit on number of MSI interrupts.
|
||||
In this case the function could look like this:
|
||||
|
||||
static int foo_driver_enable_msi(struct pci_dev *pdev, int nvec)
|
||||
{
|
||||
return pci_enable_msi_range(pdev, FOO_DRIVER_MINIMUM_NVEC, nvec);
|
||||
}
|
||||
|
||||
4.2.1.2 Exact number of MSI interrupts
|
||||
|
||||
If a driver is unable or unwilling to deal with a variable number of MSI
|
||||
interrupts it could request a particular number of interrupts by passing
|
||||
that number to pci_enable_msi_range() function as both 'minvec' and 'maxvec'
|
||||
parameters:
|
||||
|
||||
static int foo_driver_enable_msi(struct pci_dev *pdev, int nvec)
|
||||
{
|
||||
return pci_enable_msi_range(pdev, nvec, nvec);
|
||||
}
|
||||
|
||||
4.2.1.3 Single MSI mode
|
||||
|
||||
The most notorious example of the request type described above is
|
||||
enabling the single MSI mode for a device. It could be done by passing
|
||||
two 1s as 'minvec' and 'maxvec':
|
||||
|
||||
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
|
||||
|
||||
void pci_disable_msi(struct pci_dev *dev)
|
||||
|
||||
This function should be used to undo the effect of pci_enable_msi() or
|
||||
pci_enable_msi_block(). Calling it restores dev->irq to the pin-based
|
||||
interrupt number and frees the previously allocated message signaled
|
||||
interrupt(s). The interrupt may subsequently be assigned to another
|
||||
device, so drivers should not cache the value of dev->irq.
|
||||
This function should be used to undo the effect of pci_enable_msi_range().
|
||||
Calling it restores dev->irq to the pin-based interrupt number and frees
|
||||
the previously allocated MSIs. The interrupts may subsequently be assigned
|
||||
to another device, so drivers should not cache the value of dev->irq.
|
||||
|
||||
Before calling this function, a device driver must always call free_irq()
|
||||
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.
|
||||
|
||||
4.2.4 pci_msi_vec_count
|
||||
4.2.3 pci_msi_vec_count
|
||||
|
||||
int pci_msi_vec_count(struct pci_dev *dev)
|
||||
|
||||
|
|
@ -176,26 +206,31 @@ in each element of the array to indicate for which entries the kernel
|
|||
should assign interrupts; it is invalid to fill in two entries with the
|
||||
same number.
|
||||
|
||||
4.3.1 pci_enable_msix
|
||||
4.3.1 pci_enable_msix_range
|
||||
|
||||
int pci_enable_msix(struct pci_dev *dev, struct msix_entry *entries, int nvec)
|
||||
int pci_enable_msix_range(struct pci_dev *dev, struct msix_entry *entries,
|
||||
int minvec, int maxvec)
|
||||
|
||||
Calling this function asks the PCI subsystem to allocate 'nvec' MSIs.
|
||||
Calling this function asks the PCI subsystem to allocate any number of
|
||||
MSI-X interrupts within specified range from 'minvec' to 'maxvec'.
|
||||
The 'entries' argument is a pointer to an array of msix_entry structs
|
||||
which should be at least 'nvec' entries in size. On success, the
|
||||
device is switched into MSI-X mode and the function returns 0.
|
||||
The 'vector' member in each entry is populated with the interrupt number;
|
||||
which should be at least 'maxvec' entries in size.
|
||||
|
||||
On success, the device is switched into MSI-X mode and the function
|
||||
returns the number of MSI-X interrupts that have been successfully
|
||||
allocated. In this case the 'vector' member in entries numbered from
|
||||
0 to the returned value - 1 is populated with the interrupt number;
|
||||
the driver should then call request_irq() for each 'vector' that it
|
||||
decides to use. The device driver is responsible for keeping track of the
|
||||
interrupts assigned to the MSI-X vectors so it can free them again later.
|
||||
Device driver can use the returned number of successfully allocated MSI-X
|
||||
interrupts to further allocate and initialize device resources.
|
||||
|
||||
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. If it returns a positive number, it indicates the maximum
|
||||
number of interrupt vectors that could have been allocated. See example
|
||||
below.
|
||||
this device.
|
||||
|
||||
This function, in contrast with pci_enable_msi(), does not adjust
|
||||
This function, in contrast with pci_enable_msi_range(), does not adjust
|
||||
dev->irq. The device will not generate interrupts for this interrupt
|
||||
number once MSI-X is enabled.
|
||||
|
||||
|
|
@ -206,28 +241,103 @@ It is ideal if drivers can cope with a variable number of MSI-X interrupts;
|
|||
there are many reasons why the platform may not be able to provide the
|
||||
exact number that a driver asks for.
|
||||
|
||||
A request loop to achieve that might look like:
|
||||
There could be devices that can not operate with just any number of MSI-X
|
||||
interrupts within a range. E.g., an network adapter might need let's say
|
||||
four vectors per each queue it provides. Therefore, a number of MSI-X
|
||||
interrupts allocated should be a multiple of four. In this case interface
|
||||
pci_enable_msix_range() can not be used alone to request MSI-X interrupts
|
||||
(since it can allocate any number within the range, without any notion of
|
||||
the multiple of four) and the device driver should master a custom logic
|
||||
to request the required number of MSI-X interrupts.
|
||||
|
||||
4.3.1.1 Maximum possible number of MSI-X interrupts
|
||||
|
||||
The typical usage of MSI-X interrupts is to allocate as many vectors as
|
||||
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)
|
||||
{
|
||||
while (nvec >= FOO_DRIVER_MINIMUM_NVEC) {
|
||||
rc = pci_enable_msix(adapter->pdev,
|
||||
adapter->msix_entries, nvec);
|
||||
if (rc > 0)
|
||||
nvec = rc;
|
||||
else
|
||||
return rc;
|
||||
return pci_enable_msi_range(adapter->pdev, adapter->msix_entries,
|
||||
1, nvec);
|
||||
}
|
||||
|
||||
Note the value of 'minvec' parameter is 1. As 'minvec' is inclusive,
|
||||
the value of 0 would be meaningless and could result in error.
|
||||
|
||||
Some devices have a minimal limit on number of MSI-X interrupts.
|
||||
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);
|
||||
}
|
||||
|
||||
4.3.1.2 Exact number of MSI-X interrupts
|
||||
|
||||
If a driver is unable or unwilling to deal with a variable number of MSI-X
|
||||
interrupts it could request a particular number of interrupts by passing
|
||||
that number to pci_enable_msix_range() function as both 'minvec' and 'maxvec'
|
||||
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);
|
||||
}
|
||||
|
||||
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
|
||||
number of MSI-X interrupts within a range. E.g., let's assume a device that
|
||||
is only capable sending the number of MSI-X interrupts which is a power of
|
||||
two. A routine that enables MSI-X mode for such device 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_range(adapter->pdev, adapter->msix_entries,
|
||||
maxvec, maxvec);
|
||||
/*
|
||||
* -ENOSPC is the only error code allowed to be analized
|
||||
*/
|
||||
if (rc == -ENOSPC) {
|
||||
if (maxvec == 1)
|
||||
return -ENOSPC;
|
||||
|
||||
maxvec /= 2;
|
||||
|
||||
if (minvec > maxvec)
|
||||
return -ENOSPC;
|
||||
|
||||
goto retry;
|
||||
}
|
||||
|
||||
return -ENOSPC;
|
||||
return rc;
|
||||
}
|
||||
|
||||
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
|
||||
|
||||
void pci_disable_msix(struct pci_dev *dev)
|
||||
|
||||
This function should be used to undo the effect of pci_enable_msix(). It frees
|
||||
the previously allocated message signaled interrupts. The interrupts may
|
||||
This function should be used to undo the effect of pci_enable_msix_range().
|
||||
It frees the previously allocated MSI-X interrupts. The interrupts may
|
||||
subsequently be assigned to another device, so drivers should not cache
|
||||
the value of the 'vector' elements over a call to pci_disable_msix().
|
||||
|
||||
|
|
@ -261,13 +371,14 @@ number of MSI-X interrupt vectors that could be allocated.
|
|||
If a device implements both MSI and MSI-X capabilities, it can
|
||||
run in either MSI mode or MSI-X mode, but not both simultaneously.
|
||||
This is a requirement of the PCI spec, and it is enforced by the
|
||||
PCI layer. Calling pci_enable_msi() when MSI-X is already enabled or
|
||||
pci_enable_msix() when MSI is already enabled results in an error.
|
||||
If a device driver wishes to switch between MSI and MSI-X at runtime,
|
||||
it must first quiesce the device, then switch it back to pin-interrupt
|
||||
mode, before calling pci_enable_msi() or pci_enable_msix() and resuming
|
||||
operation. This is not expected to be a common operation but may be
|
||||
useful for debugging or testing during development.
|
||||
PCI layer. Calling pci_enable_msi_range() when MSI-X is already
|
||||
enabled or pci_enable_msix_range() when MSI is already enabled
|
||||
results in an error. If a device driver wishes to switch between MSI
|
||||
and MSI-X at runtime, it must first quiesce the device, then switch
|
||||
it back to pin-interrupt mode, before calling pci_enable_msi_range()
|
||||
or pci_enable_msix_range() and resuming operation. This is not expected
|
||||
to be a common operation but may be useful for debugging or testing
|
||||
during development.
|
||||
|
||||
4.5 Considerations when using MSIs
|
||||
|
||||
|
|
@ -382,5 +493,5 @@ or disabled (0). If 0 is found in any of the msi_bus files belonging
|
|||
to bridges between the PCI root and the device, MSIs are disabled.
|
||||
|
||||
It is also worth checking the device driver to see whether it supports MSIs.
|
||||
For example, it may contain calls to pci_enable_msi(), pci_enable_msix() or
|
||||
pci_enable_msi_block().
|
||||
For example, it may contain calls to pci_enable_msi_range() or
|
||||
pci_enable_msix_range().
|
||||
|
|
|
|||
|
|
@ -1102,3 +1102,77 @@ void pci_msi_init_pci_dev(struct pci_dev *dev)
|
|||
if (dev->msix_cap)
|
||||
msix_set_enable(dev, 0);
|
||||
}
|
||||
|
||||
/**
|
||||
* pci_enable_msi_range - configure device's MSI capability structure
|
||||
* @dev: device to configure
|
||||
* @minvec: minimal number of interrupts to configure
|
||||
* @maxvec: maximum number of interrupts to configure
|
||||
*
|
||||
* This function tries to allocate a maximum possible number of interrupts in a
|
||||
* range between @minvec and @maxvec. It returns a negative errno if an error
|
||||
* occurs. If it succeeds, it returns the actual number of interrupts allocated
|
||||
* and updates the @dev's irq member to the lowest new interrupt number;
|
||||
* the other interrupt numbers allocated to this device are consecutive.
|
||||
**/
|
||||
int pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec)
|
||||
{
|
||||
int nvec = maxvec;
|
||||
int rc;
|
||||
|
||||
if (maxvec < minvec)
|
||||
return -ERANGE;
|
||||
|
||||
do {
|
||||
rc = pci_enable_msi_block(dev, nvec);
|
||||
if (rc < 0) {
|
||||
return rc;
|
||||
} else if (rc > 0) {
|
||||
if (rc < minvec)
|
||||
return -ENOSPC;
|
||||
nvec = rc;
|
||||
}
|
||||
} while (rc);
|
||||
|
||||
return nvec;
|
||||
}
|
||||
EXPORT_SYMBOL(pci_enable_msi_range);
|
||||
|
||||
/**
|
||||
* pci_enable_msix_range - configure device's MSI-X capability structure
|
||||
* @dev: pointer to the pci_dev data structure of MSI-X device function
|
||||
* @entries: pointer to an array of MSI-X entries
|
||||
* @minvec: minimum number of MSI-X irqs requested
|
||||
* @maxvec: maximum number of MSI-X irqs requested
|
||||
*
|
||||
* Setup the MSI-X capability structure of device function with a maximum
|
||||
* possible number of interrupts in the range between @minvec and @maxvec
|
||||
* upon its software driver call to request for MSI-X mode enabled on its
|
||||
* hardware device function. It returns a negative errno if an error occurs.
|
||||
* If it succeeds, it returns the actual number of interrupts allocated and
|
||||
* indicates the successful configuration of MSI-X capability structure
|
||||
* with new allocated MSI-X interrupts.
|
||||
**/
|
||||
int pci_enable_msix_range(struct pci_dev *dev, struct msix_entry *entries,
|
||||
int minvec, int maxvec)
|
||||
{
|
||||
int nvec = maxvec;
|
||||
int rc;
|
||||
|
||||
if (maxvec < minvec)
|
||||
return -ERANGE;
|
||||
|
||||
do {
|
||||
rc = pci_enable_msix(dev, entries, nvec);
|
||||
if (rc < 0) {
|
||||
return rc;
|
||||
} else if (rc > 0) {
|
||||
if (rc < minvec)
|
||||
return -ENOSPC;
|
||||
nvec = rc;
|
||||
}
|
||||
} while (rc);
|
||||
|
||||
return nvec;
|
||||
}
|
||||
EXPORT_SYMBOL(pci_enable_msix_range);
|
||||
|
|
|
|||
|
|
@ -1193,6 +1193,17 @@ static inline int pci_msi_enabled(void)
|
|||
{
|
||||
return 0;
|
||||
}
|
||||
|
||||
static inline int pci_enable_msi_range(struct pci_dev *dev, int minvec,
|
||||
int maxvec)
|
||||
{
|
||||
return -ENOSYS;
|
||||
}
|
||||
static inline int pci_enable_msix_range(struct pci_dev *dev,
|
||||
struct msix_entry *entries, int minvec, int maxvec)
|
||||
{
|
||||
return -ENOSYS;
|
||||
}
|
||||
#else
|
||||
int pci_msi_vec_count(struct pci_dev *dev);
|
||||
int pci_enable_msi_block(struct pci_dev *dev, int nvec);
|
||||
|
|
@ -1205,6 +1216,9 @@ void pci_disable_msix(struct pci_dev *dev);
|
|||
void msi_remove_pci_irq_vectors(struct pci_dev *dev);
|
||||
void pci_restore_msi_state(struct pci_dev *dev);
|
||||
int pci_msi_enabled(void);
|
||||
int pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec);
|
||||
int pci_enable_msix_range(struct pci_dev *dev, struct msix_entry *entries,
|
||||
int minvec, int maxvec);
|
||||
#endif
|
||||
|
||||
#ifdef CONFIG_PCIEPORTBUS
|
||||
|
|
|
|||
Загрузка…
Ссылка в новой задаче