On Mon, Sep 24, 2018 at 03:10:40PM +0200, Thomas Petazzoni wrote:
> 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().
I understand that, I wanted to make sure we come up with a fix asap
and what I put forward would cover everything discussed in this thread,
at least temporarily, giving us time to check ISA related issues while
unmapping IO space.
Lorenzo
