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Message-ID: <20240911140721.GA630378@bhelgaas>
Date: Wed, 11 Sep 2024 09:07:21 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Frank Li <Frank.Li@....com>
Cc: Richard Zhu <hongxing.zhu@....com>,
Lucas Stach <l.stach@...gutronix.de>,
Lorenzo Pieralisi <lpieralisi@...nel.org>,
Krzysztof WilczyĆski <kw@...ux.com>,
Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
Shawn Guo <shawnguo@...nel.org>,
Sascha Hauer <s.hauer@...gutronix.de>,
Pengutronix Kernel Team <kernel@...gutronix.de>,
Fabio Estevam <festevam@...il.com>,
NXP Linux Team <linux-imx@....com>,
Philipp Zabel <p.zabel@...gutronix.de>,
Liam Girdwood <lgirdwood@...il.com>,
Mark Brown <broonie@...nel.org>,
Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Conor Dooley <conor+dt@...nel.org>, linux-pci@...r.kernel.org,
imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
devicetree@...r.kernel.org, Qianqiang Liu <qianqiang.liu@....com>
Subject: Re: [PATCH v8 11/11] PCI: imx6: Add i.MX8Q PCIe root complex (RC)
support
[+cc Qianqiang]
On Mon, Jul 29, 2024 at 04:18:18PM -0400, Frank Li wrote:
> From: Richard Zhu <hongxing.zhu@....com>
>
> Implement i.MX8Q (i.MX8QM, i.MX8QXP, and i.MX8DXL) PCIe RC support. While
> the controller resembles that of iMX8MP, the PHY differs significantly.
> Notably, there's a distinction between PCI bus addresses and CPU addresses.
>
> Introduce IMX_PCIE_FLAG_CPU_ADDR_FIXUP in drvdata::flags to indicate driver
> need the cpu_addr_fixup() callback to facilitate CPU address to PCI bus
> address conversion according to "ranges" property.
> +static u64 imx_pcie_cpu_addr_fixup(struct dw_pcie *pcie, u64 cpu_addr)
> +{
> + struct imx_pcie *imx_pcie = to_imx_pcie(pcie);
> + struct dw_pcie_rp *pp = &pcie->pp;
> + struct resource_entry *entry;
> + unsigned int offset;
> +
> + if (!(imx_pcie->drvdata->flags & IMX_PCIE_FLAG_CPU_ADDR_FIXUP))
> + return cpu_addr;
> +
> + entry = resource_list_first_type(&pp->bridge->windows, IORESOURCE_MEM);
> + offset = entry->offset;
> + return (cpu_addr - offset);
> +}
I'm sure that with enough effort, we could prove "entry" cannot be
NULL here, but I'm not sure I want to spend the effort, and we're
going to end up with more patches like this:
https://lore.kernel.org/r/20240911125055.58555-1-qianqiang.liu@163.com
I propose this minor change:
entry = resource_list_first_type(&pp->bridge->windows, IORESOURCE_MEM);
if (!entry)
return cpu_addr;
return cpu_addr - entry->offset;
I still think we should get rid of the .cpu_addr_fixup() callback if
possible. But that's a discussion for another day.
Bjorn
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