[PATCH v4 3/4] PCI: dwc: Reduce DT reads by allocating host bridge via DWC glue driver

Krishna Chaitanya Chundru
2025-02-06T23:29:27Z

dw_pcie_ecam_supported() needs to read bus-range to find the maximum
bus range value. The devm_pci_alloc_host_bridge() is already reading
bus range and storing it in host bridge.If devm_pci_alloc_host_bridge()
moved to start of the controller probe, the dt reading can be avoided
and use values stored in the host bridge.

Allow DWC glue drivers to allocate the host bridge, avoiding redundant
device tree reads primarily in dw_pcie_ecam_supported().

Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
---
drivers/pci/controller/dwc/pcie-designware-host.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index 826ff9338646..a18cb1e411e4 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -484,8 +484,8 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
struct device *dev = pci->dev;
struct device_node *np = dev->of_node;
struct platform_device *pdev = to_platform_device(dev);
+ struct pci_host_bridge *bridge = pp->bridge;
struct resource_entry *win;
- struct pci_host_bridge *bridge;
struct resource *res;
int ret;

@@ -527,7 +527,12 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
if (!bridge)
return -ENOMEM;

- pp->bridge = bridge;
+ if (!pp->bridge) {
+ bridge = devm_pci_alloc_host_bridge(dev, 0);
+ if (!bridge)
+ return -ENOMEM;
+ pp->bridge = bridge;
+ }

/* Get the I/O range from DT */
win = resource_list_first_type(&bridge->windows, IORESOURCE_IO);

--
2.34.1