Re: [PATCH] PCI: mvebu: Fix PCI I/O mapping creation sequence

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

On Mon, Oct 01, 2018 at 02:49:34PM +0200, Thomas Petazzoni wrote:
> Commit ee1604381a371 ("PCI: mvebu: Only remap I/O space if
> configured") had the side effect that the PCI I/O mapping was created
> much earlier than before, at a point where the probe() of the driver
> could still fail. This is for example a problem if one gets an
> -EPROBE_DEFER at some point during probe(), after pci_ioremap_io() has
> been called.
> 
> Indeed, there is currently no function to undo what pci_ioremap_io()
> did, and switching to pci_remap_iospace() is not an option in
> pci-mvebu due to the need for special memory attributes on Armada 38x.
> 
> Reverting ee1604381a371 ("PCI: mvebu: Only remap I/O space if
> configured") would be a possibility, but it would require also
> reverting 42342073e38b5 ("PCI: mvebu: Convert to use pci_host_bridge
> directly"). So instead, we use an open-coded version of
> pci_host_probe() that creates the PCI I/O mapping at a point where we
> are guaranteed not to fail anymore.
> 
> Reported-by: Jan Kundrát <jan.kundrat@cesnet.cz>
> Fixes: ee1604381a371 ("PCI: mvebu: Only remap I/O space if configured")
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
> ---
>  drivers/pci/controller/pci-mvebu.c | 52 +++++++++++++++++++++++++++++++++++---
>  1 file changed, 48 insertions(+), 4 deletions(-)

Thank you Thomas.

Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

Bjorn, is it possible please to send this patch for -rc7 ? It is
a regression we introduced in the last cycle.

Thanks,
Lorenzo

> diff --git a/drivers/pci/controller/pci-mvebu.c b/drivers/pci/controller/pci-mvebu.c
> index 50eb0729385b..a41d79b8d46a 100644
> --- a/drivers/pci/controller/pci-mvebu.c
> +++ b/drivers/pci/controller/pci-mvebu.c
> @@ -1145,7 +1145,6 @@ static int mvebu_pcie_parse_request_resources(struct mvebu_pcie *pcie)
>  {
>  	struct device *dev = &pcie->pdev->dev;
>  	struct device_node *np = dev->of_node;
> -	unsigned int i;
>  	int ret;
>  
>  	INIT_LIST_HEAD(&pcie->resources);
> @@ -1179,13 +1178,58 @@ static int mvebu_pcie_parse_request_resources(struct mvebu_pcie *pcie)
>  					 resource_size(&pcie->io) - 1);
>  		pcie->realio.name = "PCI I/O";
>  
> +		pci_add_resource(&pcie->resources, &pcie->realio);
> +	}
> +
> +	return devm_request_pci_bus_resources(dev, &pcie->resources);
> +}
> +
> +/*
> + * This is a copy of pci_host_probe(), except that it does the I/O
> + * remap as the last step, once we are sure we won't fail.
> + *
> + * It should be removed once the I/O remap error handling issue has
> + * been sorted out.
> + */
> +static int mvebu_pci_host_probe(struct pci_host_bridge *bridge)
> +{
> +	struct mvebu_pcie *pcie;
> +	struct pci_bus *bus, *child;
> +	int ret;
> +
> +	ret = pci_scan_root_bus_bridge(bridge);
> +	if (ret < 0) {
> +		dev_err(bridge->dev.parent, "Scanning root bridge failed");
> +		return ret;
> +	}
> +
> +	pcie = pci_host_bridge_priv(bridge);
> +	if (resource_size(&pcie->io) != 0) {
> +		unsigned int i;
> +
>  		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);
> +	bus = bridge->bus;
> +
> +	/*
> +	 * We insert PCI resources into the iomem_resource and
> +	 * ioport_resource trees in either pci_bus_claim_resources()
> +	 * or pci_bus_assign_resources().
> +	 */
> +	if (pci_has_flag(PCI_PROBE_ONLY)) {
> +		pci_bus_claim_resources(bus);
> +	} else {
> +		pci_bus_size_bridges(bus);
> +		pci_bus_assign_resources(bus);
> +
> +		list_for_each_entry(child, &bus->children, node)
> +			pcie_bus_configure_settings(child);
>  	}
>  
> -	return devm_request_pci_bus_resources(dev, &pcie->resources);
> +	pci_bus_add_devices(bus);
> +	return 0;
>  }
>  
>  static int mvebu_pcie_probe(struct platform_device *pdev)
> @@ -1268,7 +1312,7 @@ 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);
> +	return mvebu_pci_host_probe(bridge);
>  }
>  
>  static const struct of_device_id mvebu_pcie_of_match_table[] = {
> -- 
> 2.14.4
>