[PATCH 1/6] PCI: don't clear already cleared bit

Stewart Hildebrand
2024-07-09T13:36:25Z

pci_reassigndev_resource_alignment() performs a PCI config read, then
then unconditionally clears a bit and issues a PCI config write.
However, the bit in question (PCI_COMMAND_MEMORY) is a RW bit, so it is
unnecessary to issue the PCI config write if the bit is already cleared.
Make the write conditional.

Signed-off-by: Stewart Hildebrand <stewart.hildebrand@amd.com>
---
Should this be folded into ("pci: restore memory decoding after
reallocation") in this series?
---
drivers/pci/pci.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index df550953fa26..f017e7a8f028 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -6632,8 +6632,10 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev)
}

pci_read_config_word(dev, PCI_COMMAND, &command);
- command &= ~PCI_COMMAND_MEMORY;
- pci_write_config_word(dev, PCI_COMMAND, command);
+ if (command & PCI_COMMAND_MEMORY) {
+ command &= ~PCI_COMMAND_MEMORY;
+ pci_write_config_word(dev, PCI_COMMAND, command);
+ }

for (i = 0; i <= PCI_ROM_RESOURCE; i++)
pci_request_resource_alignment(dev, i, align, resize);
--
2.45.2