linux-kernel - Re: [PATCH v3 3/4] PCI: dwc: Reduce DT reads by allocating host bridge via DWC glue driver

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Message-ID: <20250124061828.ncycdpxqd6fqpjib@thinkpad>
Date: Fri, 24 Jan 2025 11:48:28 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
Cc: cros-qcom-dts-watchers@...omium.org,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konradybcio@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Jingoo Han <jingoohan1@...il.com>, linux-arm-msm@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, quic_vbadigan@...cinc.com,
	quic_vpernami@...cinc.com, quic_mrana@...cinc.com,
	mmareddy@...cinc.com,
	Krishna chaitanya chundru <quic_krichai@...cinc.com>
Subject: Re: [PATCH v3 3/4] PCI: dwc: Reduce DT reads by allocating host
 bridge via DWC glue driver

On Tue, Jan 21, 2025 at 02:32:21PM +0530, Krishna Chaitanya Chundru wrote:
> Allow DWC glue drivers to allocate the host bridge, avoiding redundant
> device tree reads primarily in dw_pcie_ecam_supported().
> 

I don't understand what you mean by 'redundant device tree reads'. Please
explain.

- Mani

> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
> ---
>  drivers/pci/controller/dwc/pcie-designware-host.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index 3888f9fe5af1..0acf9db44f2c 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;
>  
> @@ -497,11 +497,12 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
>  		return -ENODEV;
>  	}
>  
> -	bridge = devm_pci_alloc_host_bridge(dev, 0);
> -	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;
> +	}
>  
>  	pp->cfg0_size = resource_size(res);
>  	pp->cfg0_base = res->start;
> 
> -- 
> 2.34.1
> 

-- 
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