[PATCH] msi: skip calling pci_find_capability from msi_set_mask_bits

From: Hidetoshi Seto
Date: Mon May 19 2008 - 00:49:32 EST

Jesse Barnes wrote:
> Since we know MSI is a problem, let's just go with fixing that for now. If we
> find that other caps are also causing problems we can revisit caching all of
> them; the patch is simple enough.

I suppose it can be more simple. How about this patch?

> everytime handle_edge_irq is called it needs to mask and unmask MSI, and
> that leads to a series of very expensive calls to pci_find_capability

The position of MSI capability is already cached in the msi_desc when
we enter the msi_set_mask_bits(). Use it instead.

Signed-off-by: Hidetoshi Seto <seto.hidetoshi@xxxxxxxxxxxxxx>
drivers/pci/msi.c | 12 ++++++++----
1 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 8c61304..ccb1974 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -70,12 +70,10 @@ arch_teardown_msi_irqs(struct pci_dev *dev)

-static void msi_set_enable(struct pci_dev *dev, int enable)
+static void __msi_set_enable(struct pci_dev *dev, int pos, int enable)
- int pos;
u16 control;

- pos = pci_find_capability(dev, PCI_CAP_ID_MSI);
if (pos) {
pci_read_config_word(dev, pos + PCI_MSI_FLAGS, &control);
@@ -85,6 +83,11 @@ static void msi_set_enable(struct pci_dev *dev, int enable)

+static void msi_set_enable(struct pci_dev *dev, int enable)
+ __msi_set_enable(dev, pci_find_capability(dev, PCI_CAP_ID_MSI), enable);
static void msix_set_enable(struct pci_dev *dev, int enable)
int pos;
@@ -141,7 +144,8 @@ static void msi_set_mask_bits(unsigned int irq, u32 mask, u32 flag)
mask_bits |= flag & mask;
pci_write_config_dword(entry->dev, pos, mask_bits);
} else {
- msi_set_enable(entry->dev, !flag);
+ __msi_set_enable(entry->dev, entry->msi_attrib.pos,
+ !flag);

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