Re: [PATCH v9 4/7] PCI: dwc: Use devicetree 'ranges' property to get rid of cpu_addr_fixup() callback
From: Bjorn Helgaas <helgaas@kernel.org>
Date: 2025-02-26 23:33:42
Also in:
imx, linux-devicetree, linux-pci, lkml
On Tue, Jan 28, 2025 at 05:07:37PM -0500, Frank Li wrote:
parent_bus_offset in resource_entry can indicate address information just ahead of PCIe controller. Most system's bus fabric use 1:1 map between input and output address. but some hardware like i.MX8QXP doesn't use 1:1 map. See below diagram: ...
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@@ -448,6 +451,26 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp) if (IS_ERR(pp->va_cfg0_base)) return PTR_ERR(pp->va_cfg0_base); + if (pci->use_parent_dt_ranges) { + if (pci->ops->cpu_addr_fixup) { + dev_err(dev, "Use parent bus DT ranges, cpu_addr_fixup() must be removed\n"); + return -EINVAL; + } + + index = of_property_match_string(np, "reg-names", "config"); + if (index < 0) + return -EINVAL; + + /* + * Retrieve the parent bus address of PCI config space. + * If the parent bus ranges in the device tree provide + * the correct address conversion information, set + * 'use_parent_dt_ranges' to true, The + * 'cpu_addr_fixup()' can be eliminated. + */ + of_property_read_reg(np, index, &pp->cfg0_base, NULL); + }
I think all this code dealing with the "config" resource could go in a helper function. It's kind of a lot of clutter in dw_pcie_host_init(). It would be nice to assign pp->cfg0_base once, not assign res->start to it and then possibly overwrite it later.
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@@ -841,6 +841,15 @@ void dw_pcie_iatu_detect(struct dw_pcie *pci) pci->region_align = 1 << fls(min); pci->region_limit = (max << 32) | (SZ_4G - 1); + if (pci->ops && pci->ops->cpu_addr_fixup) { + /* + * If the parent 'ranges' property in DT correctly describes + * the address translation, cpu_addr_fixup() callback is not + * needed. + */ + dev_warn_once(pci->dev, "cpu_addr_fixup() usage detected. Please fix DT!\n"); + }
Can you split the warnings out to a separate patch? I think we should warn once in every initialization path where .cpu_addr_fixup() could be used, i.e., dw_pcie_host_init() dw_pcie_ep_init() cdns_pcie_host_setup() cdns_pcie_ep_setup() IMO these should warn if .cpu_addr_fixup() is implemented, regardless of use_parent_dt_ranges. I'm still puzzling over some of the rest of this, so no need to post a revised series yet. Bjorn