linux-kernel - Re: [PATCH v9 2/7] PCI: dwc: Rename cpu_addr to parent_bus

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Message-ID: <20250129232350.GA527937@bhelgaas>
Date: Wed, 29 Jan 2025 17:23:50 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Frank Li <Frank.Li@....com>
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>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Richard Zhu <hongxing.zhu@....com>,
	Lucas Stach <l.stach@...gutronix.de>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, imx@...ts.linux.dev,
	Niklas Cassel <cassel@...nel.org>
Subject: Re: [PATCH v9 2/7] PCI: dwc: Rename cpu_addr to parent_bus_addr for
 ATU configuration

On Tue, Jan 28, 2025 at 05:07:35PM -0500, Frank Li wrote:
> Rename `cpu_addr` to `parent_bus_addr` in the DesignWare ATU configuration.
> The ATU translates parent bus addresses to PCI addresses, which are often
> the same as CPU addresses but can differ in systems where the bus fabric
> translates addresses before passing them to the PCIe controller. This
> renaming clarifies the purpose and avoids confusion.

Based on dw_pcie_ep_inbound_atu() below, I guess the ATU can also
translate PCI addresses from incoming DMA to parent bus addresses?

It's worth noting here that this patch only renames the member, and
IIUC, parent_bus_addr still incorrectly contains CPU physical
addresses.

> +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
> @@ -128,7 +128,7 @@ static int dw_pcie_ep_write_header(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
>  }
>  
>  static int dw_pcie_ep_inbound_atu(struct dw_pcie_ep *ep, u8 func_no, int type,
> -				  dma_addr_t cpu_addr, enum pci_barno bar,
> +				  dma_addr_t parent_bus_addr, enum pci_barno bar,
>  				  size_t size)