If alignment is requested for a device and all the BARs are already
sufficiently aligned, there is no need to disable memory decoding for
the device. Add a check for this scenario to save a PCI config space
access.
Also, there is no need to disable memory decoding if already disabled,
since the bit in question (PCI_COMMAND_MEMORY) is a RW bit. Make the
write conditional to save a PCI config space access.
Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
---
v2->v3:
* no change
v1->v2:
* new subject (was: "PCI: don't clear already cleared bit")
* don't disable memory decoding if alignment is not needed
---
drivers/pci/pci.c | 31 +++++++++++++++++++++----------
1 file changed, 21 insertions(+), 10 deletions(-)
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index e3a49f66982d..acecdd6edd5a 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -6564,7 +6564,7 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev,
return align;
}
-static void pci_request_resource_alignment(struct pci_dev *dev, int bar,
+static bool pci_request_resource_alignment(struct pci_dev *dev, int bar,
resource_size_t align, bool resize)
{
struct resource *r = &dev->resource[bar];
@@ -6572,17 +6572,17 @@ static void pci_request_resource_alignment(struct pci_dev *dev, int bar,
resource_size_t size;
if (!(r->flags & IORESOURCE_MEM))
- return;
+ return false;
if (r->flags & IORESOURCE_PCI_FIXED) {
pci_info(dev, "%s %pR: ignoring requested alignment %#llx\n",
r_name, r, (unsigned long long)align);
- return;
+ return false;
}
size = resource_size(r);
if (size >= align)
- return;
+ return false;
/*
* Increase the alignment of the resource. There are two ways we
@@ -6625,6 +6625,8 @@ static void pci_request_resource_alignment(struct pci_dev *dev, int bar,
r->end = r->start + size - 1;
}
r->flags |= IORESOURCE_UNSET;
+
+ return true;
}
/*
@@ -6640,7 +6642,7 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev)
struct resource *r;
resource_size_t align;
u16 command;
- bool resize = false;
+ bool resize = false, align_needed = false;
/*
* VF BARs are read-only zero according to SR-IOV spec r1.1, sec
@@ -6662,12 +6664,21 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev)
return;
}
- pci_read_config_word(dev, PCI_COMMAND, &command);
- command &= ~PCI_COMMAND_MEMORY;
- pci_write_config_word(dev, PCI_COMMAND, command);
+ for (i = 0; i <= PCI_ROM_RESOURCE; i++) {
+ bool ret;
- for (i = 0; i <= PCI_ROM_RESOURCE; i++)
- pci_request_resource_alignment(dev, i, align, resize);
+ ret = pci_request_resource_alignment(dev, i, align, resize);
+ align_needed = align_needed || ret;
+ }
+
+ if (!align_needed)
+ return;
+
+ pci_read_config_word(dev, PCI_COMMAND, &command);
+ if (command & PCI_COMMAND_MEMORY) {
+ command &= ~PCI_COMMAND_MEMORY;
+ pci_write_config_word(dev, PCI_COMMAND, command);
+ }
/*
* Need to disable bridge's resource window,
--
2.46.0
