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Date: Sun, 7 Oct 2012 07:26:32 +0200
From: Alexander Gordeev <agordeev@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: Ingo Molnar <mingo@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Suresh Siddha <suresh.b.siddha@...el.com>,
Yinghai Lu <yinghai@...nel.org>,
Jeff Garzik <jgarzik@...ox.com>,
Matthew Wilcox <willy@...ux.intel.com>, x86@...nel.org,
linux-pci@...r.kernel.org, linux-ide@...r.kernel.org
Subject: [PATCH v4 -tip 2/3] PCI, MSI: Enable multiple MSIs with
pci_enable_msi_block_auto()
The new function pci_enable_msi_block_auto() tries to allocate maximum
possible number of MSIs up to the number the device supports. It
generalizes a pattern when pci_enable_msi_block() is contiguously called
until it succeeds or fails.
Opposite to pci_enable_msi_block() which takes the number of MSIs to
allocate as a input parameter, pci_enable_msi_block_auto() could be used
by device drivers to obtain the number of assigned MSIs and the number
of MSIs the device supports.
Signed-off-by: Alexander Gordeev <agordeev@...hat.com>
Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>
---
Documentation/PCI/MSI-HOWTO.txt | 37 ++++++++++++++++++++++++++++++++-----
drivers/pci/msi.c | 26 ++++++++++++++++++++++++++
include/linux/pci.h | 7 +++++++
3 files changed, 65 insertions(+), 5 deletions(-)
diff --git a/Documentation/PCI/MSI-HOWTO.txt b/Documentation/PCI/MSI-HOWTO.txt
index 53e6fca..a091780 100644
--- a/Documentation/PCI/MSI-HOWTO.txt
+++ b/Documentation/PCI/MSI-HOWTO.txt
@@ -127,15 +127,42 @@ 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.
-4.2.3 pci_disable_msi
+4.2.3 pci_enable_msi_block_auto
+
+int pci_enable_msi_block_auto(struct pci_dev *dev, unsigned int *count)
+
+This variation on pci_enable_msi() call allows a device driver to request
+the maximum possible number of 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 a positive number, it indicates that it has
+succeeded and the returned value is the number of allocated interrupts. 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 + returned
+value - 1.
+
+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 the device driver needs to know the number of interrupts the device
+supports it can pass the pointer count where that number is stored. The
+device driver must decide what action to take if pci_enable_msi_block_auto()
+succeeds, but returns a value less than the number of interrupts supported.
+If the device driver does not need to know the number of interrupts
+supported, it can set the pointer count to NULL.
+
+4.2.4 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.
+pci_enable_msi_block() or pci_enable_msi_block_auto(). 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.
Before calling this function, a device driver must always call free_irq()
on any interrupt for which it previously called request_irq().
diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index a825d78..6ec44e2 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -839,6 +839,32 @@ int pci_enable_msi_block(struct pci_dev *dev, unsigned int nvec)
}
EXPORT_SYMBOL(pci_enable_msi_block);
+int pci_enable_msi_block_auto(struct pci_dev *dev, unsigned int *maxvec)
+{
+ int ret, pos, nvec;
+ u16 msgctl;
+
+ pos = pci_find_capability(dev, PCI_CAP_ID_MSI);
+ if (!pos)
+ return -EINVAL;
+
+ pci_read_config_word(dev, pos + PCI_MSI_FLAGS, &msgctl);
+ ret = 1 << ((msgctl & PCI_MSI_FLAGS_QMASK) >> 1);
+
+ if (maxvec)
+ *maxvec = ret;
+
+ do {
+ nvec = ret;
+ ret = pci_enable_msi_block(dev, nvec);
+ } while (ret > 0);
+
+ if (ret < 0)
+ return ret;
+ return nvec;
+}
+EXPORT_SYMBOL(pci_enable_msi_block_auto);
+
void pci_msi_shutdown(struct pci_dev *dev)
{
struct msi_desc *desc;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 5faa831..b8a9454 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1070,6 +1070,12 @@ static inline int pci_enable_msi_block(struct pci_dev *dev, unsigned int nvec)
return -1;
}
+static inline int
+pci_enable_msi_block_auto(struct pci_dev *dev, unsigned int *maxvec)
+{
+ return -1;
+}
+
static inline void pci_msi_shutdown(struct pci_dev *dev)
{ }
static inline void pci_disable_msi(struct pci_dev *dev)
@@ -1101,6 +1107,7 @@ static inline int pci_msi_enabled(void)
}
#else
extern int pci_enable_msi_block(struct pci_dev *dev, unsigned int nvec);
+extern int pci_enable_msi_block_auto(struct pci_dev *dev, unsigned int *maxvec);
extern void pci_msi_shutdown(struct pci_dev *dev);
extern void pci_disable_msi(struct pci_dev *dev);
extern int pci_msix_table_size(struct pci_dev *dev);
--
1.7.7.6
--
Regards,
Alexander Gordeev
agordeev@...hat.com
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