linux-kernel - Re: [PATCH v3 8/8] PCI: dw: Add support for PCI_PROBE_ONLY/PCI_REASSIGN_ALL

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Message-ID: <20190807163654.GC16214@e121166-lin.cambridge.arm.com>
Date:   Wed, 7 Aug 2019 17:36:54 +0100
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Jonathan Chocron <jonnyc@...zon.com>
Cc:     bhelgaas@...gle.com, jingoohan1@...il.com,
        gustavo.pimentel@...opsys.com, robh+dt@...nel.org,
        mark.rutland@....com, dwmw@...zon.co.uk, benh@...nel.crashing.org,
        alisaidi@...zon.com, ronenk@...zon.com, barakw@...zon.com,
        talel@...zon.com, hanochu@...zon.com, hhhawa@...zon.com,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v3 8/8] PCI: dw: Add support for
 PCI_PROBE_ONLY/PCI_REASSIGN_ALL_BUS flags

On Tue, Jul 23, 2019 at 12:27:11PM +0300, Jonathan Chocron wrote:
> This basically aligns the usage of PCI_PROBE_ONLY and
> PCI_REASSIGN_ALL_BUS in dw_pcie_host_init() with the logic in
> pci_host_common_probe().
> 
> Now it will be possible to control via the devicetree whether to just
> probe the PCI bus (in cases where FW already configured it) or to fully
> configure it.
> 
> Signed-off-by: Jonathan Chocron <jonnyc@...zon.com>
> ---
>  .../pci/controller/dwc/pcie-designware-host.c | 23 +++++++++++++++----
>  1 file changed, 19 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index d2ca748e4c85..0a294d8aa21a 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -342,6 +342,8 @@ int dw_pcie_host_init(struct pcie_port *pp)
>  	if (!bridge)
>  		return -ENOMEM;
>  
> +	of_pci_check_probe_only();
> +
>  	ret = devm_of_pci_get_host_bridge_resources(dev, 0, 0xff,
>  					&bridge->windows, &pp->io_base);
>  	if (ret)
> @@ -474,6 +476,10 @@ int dw_pcie_host_init(struct pcie_port *pp)
>  
>  	pp->root_bus_nr = pp->busn->start;
>  
> +	/* Do not reassign bus nums if probe only */
> +	if (!pci_has_flag(PCI_PROBE_ONLY))
> +		pci_add_flags(PCI_REASSIGN_ALL_BUS);

This changes the default for bus reassignment on all DWC host (that are
!PCI_PROBE_ONLY), we should drop this line, it can trigger regressions.

If we still want to merge it as a separate change we must test it on all
DWC host bridges to make sure it does not trigger any issues with
current set-ups, that's not going to be easy though.

Lorenzo

> +
>  	bridge->dev.parent = dev;
>  	bridge->sysdata = pp;
>  	bridge->busnr = pp->root_bus_nr;
> @@ -490,11 +496,20 @@ int dw_pcie_host_init(struct pcie_port *pp)
>  	if (pp->ops->scan_bus)
>  		pp->ops->scan_bus(pp);
>  
> -	pci_bus_size_bridges(pp->root_bus);
> -	pci_bus_assign_resources(pp->root_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(pp->root_bus);
> +	} else {
> +		pci_bus_size_bridges(pp->root_bus);
> +		pci_bus_assign_resources(pp->root_bus);
>  
> -	list_for_each_entry(child, &pp->root_bus->children, node)
> -		pcie_bus_configure_settings(child);
> +		list_for_each_entry(child, &pp->root_bus->children, node)
> +			pcie_bus_configure_settings(child);
> +	}
>  
>  	pci_bus_add_devices(pp->root_bus);
>  	return 0;
> -- 
> 2.17.1
>