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    SubjectRe: [BISECTED] Regression: Solidrun Clearfog Base won't boot since "PCI: mvebu: Only remap I/O space if configured"
    Hello,

    On Mon, 24 Sep 2018 13:46:29 +0100, Lorenzo Pieralisi wrote:

    > What I think you can do short term, given that AFAICS MVEBU is not
    > removable, instead of using pci_host_probe() you move part of its code
    > into the driver and make sure that you remap IO as last operation before
    > probe completion (ie after scanning the host bridge) so that you do not
    > need to unmap it on failure; write a commit log summarising/linking this
    > thread please and when v4.20 lands we will give this a more thorough
    > look as Russell requested.
    >
    > How does that sound ?

    The only thing that can fail in pci_host_probe() is:

    ret = pci_scan_root_bus_bridge(bridge);
    if (ret < 0) {
    dev_err(bridge->dev.parent, "Scanning root bridge
    failed"); return ret;
    }

    In the pci-mvebu driver prior to the conversion to pci_host_probe(),
    the code flow at the end of ->probe() was:

    mvebu_pcie_enable()
    pci_common_init_dev()
    pcibios_init_hw()

    and pcibios_init_hw() calls pci_scan_root_bus_bridge(), without doing
    much about the return value other than issuing a warning:

    ret = pci_scan_root_bus_bridge(bridge);
    }

    if (WARN(ret < 0, "PCI: unable to scan bus!")) {
    pci_free_host_bridge(bridge);
    break;
    }

    I.e, even before the conversion to pci_host_probe(), in case of
    failure in pci_scan_root_bus_bridge(), we would have the I/O mapping in
    place, but the PCI controller not registered.

    We could keep the same (not great) behavior by doing:

    diff --git a/drivers/pci/controller/pci-mvebu.c b/drivers/pci/controller/pci-mvebu.c
    index 50eb0729385b..487492f0c5f7 100644
    --- a/drivers/pci/controller/pci-mvebu.c
    +++ b/drivers/pci/controller/pci-mvebu.c
    @@ -1179,9 +1179,6 @@ static int mvebu_pcie_parse_request_resources(struct mvebu_pcie *pcie)
    resource_size(&pcie->io) - 1);
    pcie->realio.name = "PCI I/O";

    - for (i = 0; i < resource_size(&pcie->realio); i += SZ_64K)
    - pci_ioremap_io(i, pcie->io.start + i);
    -
    pci_add_resource(&pcie->resources, &pcie->realio);
    }

    @@ -1197,7 +1194,7 @@ static int mvebu_pcie_probe(struct platform_device *pdev)
    struct device_node *child;
    int num, i, ret;

    - bridge = devm_pci_alloc_host_bridge(dev, sizeof(struct mvebu_pcie));
    + bridge = pci_alloc_host_bridge(sizeof(struct mvebu_pcie));
    if (!bridge)
    return -ENOMEM;

    @@ -1212,8 +1209,10 @@ static int mvebu_pcie_probe(struct platform_device *pdev)
    num = of_get_available_child_count(np);

    pcie->ports = devm_kcalloc(dev, num, sizeof(*pcie->ports), GFP_KERNEL);
    - if (!pcie->ports)
    - return -ENOMEM;
    + if (!pcie->ports) {
    + ret = -ENOMEM;
    + goto free_host_bridge;
    + }

    i = 0;
    for_each_available_child_of_node(np, child) {
    @@ -1222,7 +1221,7 @@ static int mvebu_pcie_probe(struct platform_device *pdev)
    ret = mvebu_pcie_parse_port(pcie, port, child);
    if (ret < 0) {
    of_node_put(child);
    - return ret;
    + goto free_host_bridge;
    } else if (ret == 0) {
    continue;
    }
    @@ -1268,7 +1267,21 @@ static int mvebu_pcie_probe(struct platform_device *pdev)
    bridge->align_resource = mvebu_pcie_align_resource;
    bridge->msi = pcie->msi;

    - return pci_host_probe(bridge);
    + if (resource_size(&pcie->io) != 0) {
    + for (i = 0; i < resource_size(&pcie->realio); i += SZ_64K)
    + pci_ioremap_io(i, pcie->io.start + i);
    + }
    +
    + ret = pci_host_probe(bridge);
    + if (ret)
    + pci_free_host_bridge(bridge);
    +
    + /* Yes, when pci_host_probe() returns a failure, we don't care */
    + return 0;
    +
    +free_host_bridge:
    + pci_free_host_bridge(bridge);
    + return ret;
    }

    static const struct of_device_id mvebu_pcie_of_match_table[] = {
    I.e, we simply ignore the failure of pci_host_probe().

    To be honest, I really prefer the option of introducing pci_unmap_io().

    Best regards,

    Thomas
    --
    Thomas Petazzoni, CTO, Bootlin
    Embedded Linux and Kernel engineering
    https://bootlin.com

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