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

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Fri, Feb 07, 2025 at 04:58:58AM +0530, Krishna Chaitanya Chundru wrote:
> 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) {

'pp->bridge' is getting dereferenced above as I indicated in patch 1.

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

There is already a previous devm_pci_alloc_host_bridge() call before this and
you are just duplicating the code here.

- Mani

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