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Subject[PATCH] PCI: Remove unnecessary re-read of SR-IOV offset/stride registers
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Previously, we read PCI_SRIOV_VF_OFFSET and PCI_SRIOV_VF_STRIDE from the
SR-IOV capability in pci_iov_set_numvfs() after changing PCI_SRIOV_NUM_VF,
and we read them again in sriov_enable(). But sriov_init() always calls
pci_iov_set_numvfs() before a successful return, and it caches the offset
and stride values, so there's no need to read the capability again in
sriov_enable().

Remove the PCI_SRIOV_VF_OFFSET and PCI_SRIOV_VF_STRIDE config reads from
sriov_enable() and use the cached values from the pci_sriov structure.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
---
drivers/pci/iov.c | 9 ++-------
1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index 0202ab0..9b52ad4 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -230,7 +230,7 @@ static int sriov_enable(struct pci_dev *dev, int nr_virtfn)
int rc;
int i, j;
int nres;
- u16 offset, stride, initial;
+ u16 initial;
struct resource *res;
struct pci_dev *pdev;
struct pci_sriov *iov = dev->sriov;
@@ -253,9 +253,7 @@ static int sriov_enable(struct pci_dev *dev, int nr_virtfn)
(!(iov->cap & PCI_SRIOV_CAP_VFM) && (nr_virtfn > initial)))
return -EINVAL;

- pci_read_config_word(dev, iov->pos + PCI_SRIOV_VF_OFFSET, &offset);
- pci_read_config_word(dev, iov->pos + PCI_SRIOV_VF_STRIDE, &stride);
- if (!offset || (nr_virtfn > 1 && !stride))
+ if (!iov->offset || (nr_virtfn > 1 && !iov->stride))
return -EIO;

nres = 0;
@@ -270,9 +268,6 @@ static int sriov_enable(struct pci_dev *dev, int nr_virtfn)
return -ENOMEM;
}

- iov->offset = offset;
- iov->stride = stride;
-
bus = pci_iov_virtfn_bus(dev, nr_virtfn - 1);
if (bus > dev->bus->busn_res.end) {
dev_err(&dev->dev, "can't enable %d VFs (bus %02x out of range of %pR)\n",


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