linux-kernel - Re: [PATCH v12 06/13] PCI: dwc: Add dw_pcie_parent_bus

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Message-ID: <Z9Yn+uY63X3Qm8ZZ@lizhi-Precision-Tower-5810>
Date: Sat, 15 Mar 2025 21:23:06 -0400
From: Frank Li <Frank.li@....com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Rob Herring <robh@...nel.org>, Saravana Kannan <saravanak@...gle.com>,
	Jingoo Han <jingoohan1@...il.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Richard Zhu <hongxing.zhu@....com>,
	Lucas Stach <l.stach@...gutronix.de>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	Niklas Cassel <cassel@...nel.org>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	imx@...ts.linux.dev, Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH v12 06/13] PCI: dwc: Add dw_pcie_parent_bus_offset()
 checking and debug

On Sat, Mar 15, 2025 at 03:15:41PM -0500, Bjorn Helgaas wrote:
> From: Frank Li <Frank.Li@....com>
>
> dw_pcie_parent_bus_offset() looks up the parent bus address of a PCI
> controller 'reg' property in devicetree.  If implemented, .cpu_addr_fixup()
> is a hard-coded way to get the parent bus address corresponding to a CPU
> physical address.
>
> Add debug code to compare the address from .cpu_addr_fixup() with the
> address from devicetree.  If they match, warn that .cpu_addr_fixup() is
> redundant and should be removed; if they differ, warn that something is
> wrong with the devicetree.
>
> If .cpu_addr_fixup() is not implemented, the parent bus address should be
> identical to the CPU physical address because we previously ignored the
> parent bus address from devicetree.  If the devicetree has a different
> parent bus address, warn about it being broken.
>
> [bhelgaas: split debug to separate patch for easier future revert, commit
> log]
> Link: https://lore.kernel.org/r/20250313-pci_fixup_addr-v11-5-01d2313502ab@nxp.com
> Signed-off-by: Frank Li <Frank.Li@....com>
> Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
> ---
>  drivers/pci/controller/dwc/pcie-designware.c | 26 +++++++++++++++++++-
>  drivers/pci/controller/dwc/pcie-designware.h | 13 ++++++++++
>  2 files changed, 38 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index 0a35e36da703..985264c88b92 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -1114,7 +1114,8 @@ resource_size_t dw_pcie_parent_bus_offset(struct dw_pcie *pci,
>  	struct device *dev = pci->dev;
>  	struct device_node *np = dev->of_node;
>  	int index;
> -	u64 reg_addr;
> +	u64 reg_addr, fixup_addr;
> +	u64 (*fixup)(struct dw_pcie *pcie, u64 cpu_addr);
>
>  	/* Look up reg_name address on parent bus */
>  	index = of_property_match_string(np, "reg-names", reg_name);
> @@ -1126,5 +1127,28 @@ resource_size_t dw_pcie_parent_bus_offset(struct dw_pcie *pci,
>
>  	of_property_read_reg(np, index, &reg_addr, NULL);
>
> +	fixup = pci->ops->cpu_addr_fixup;
> +	if (fixup) {
> +		fixup_addr = fixup(pci, cpu_phy_addr);
> +		if (reg_addr == fixup_addr) {
> +			dev_warn(dev, "%#010llx %s reg[%d] == %#010llx; %ps is redundant\n",
> +				 cpu_phy_addr, reg_name, index,
> +				 fixup_addr, fixup);
> +		} else {
> +			dev_warn(dev, "%#010llx %s reg[%d] != %#010llx fixed up addr; devicetree is broken\n",
> +				 cpu_phy_addr, reg_name,
> +				 index, fixup_addr);
> +			reg_addr = fixup_addr;
> +		}
> +	} else if (!pci->use_parent_dt_ranges) {
> +		if (reg_addr != cpu_phy_addr) {
> +			dev_warn(dev, "devicetree has incorrect translation; please check parent \"ranges\" property. CPU physical addr %#010llx, parent bus addr %#010llx\n",
> +				 cpu_phy_addr, reg_addr);
> +			return 0;
> +		}
> +	}
> +
> +	dev_info(dev, "%s parent bus offset is %#010llx\n",
> +		 reg_name, cpu_phy_addr - reg_addr);
>  	return cpu_phy_addr - reg_addr;
>  }
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 16548b01347d..f08d2852cfd5 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -465,6 +465,19 @@ struct dw_pcie {
>  	struct reset_control_bulk_data	core_rsts[DW_PCIE_NUM_CORE_RSTS];
>  	struct gpio_desc		*pe_rst;
>  	bool			suspended;
> +
> +	/*
> +	 * If iATU input addresses are offset from CPU physical addresses,
> +	 * we previously required .cpu_addr_fixup() to convert them.  We
> +	 * now rely on the devicetree instead.  If .cpu_addr_fixup()
> +	 * exists, we compare its results with devicetree.
> +	 *
> +	 * If .cpu_addr_fixup() does not exist, we assume the offset is
> +	 * zero and warn if devicetree claims otherwise.  If we know all
> +	 * devicetrees correctly describe the offset, set
> +	 * use_parent_dt_ranges to true to avoid this warning.
> +	 */
> +	bool			use_parent_dt_ranges;

Look good.

Frank

>  };
>
>  #define to_dw_pcie_from_pp(port) container_of((port), struct dw_pcie, pp)
> --
> 2.34.1
>