[RFC/RFT PATCH 08/18] PCI: designware: Convert PCI scan API to pci_scan_root_bus_bridge()

[Arnd Bergmann]

On Fri, Jun 2, 2017 at 1:49 PM, Lorenzo Pieralisi
<lorenzo.pieralisi at arm.com> wrote:
> On Fri, Apr 28, 2017 at 03:13:04PM +0200, Arnd Bergmann wrote:
>> On Wed, Apr 26, 2017 at 1:17 PM, Lorenzo Pieralisi
>> <lorenzo.pieralisi at arm.com> wrote:
>> > The introduction of pci_scan_root_bus_bridge() provides a PCI core
>> > API to scan a PCI root bus backed by an already initialized
>> > struct pci_host_bridge object, which simplifies the bus scan
>> > interface and makes the PCI scan root bus interface easier to
>> > generalize as members are added to the struct pci_host_bridge().
>> >
>> > Convert PCI designware host code to pci_scan_root_bus_bridge() to
>> > improve the PCI root bus scanning interface.
>> >
>> > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
>> > Cc: Jingoo Han <jingoohan1 at gmail.com>
>> > Cc: Bjorn Helgaas <bhelgaas at google.com>
>> > Cc: Joao Pinto <Joao.Pinto at synopsys.com>
>> > ---
>> >  drivers/pci/dwc/pcie-designware-host.c | 36 +++++++++++++++++++++-------------
>> >  1 file changed, 22 insertions(+), 14 deletions(-)
>> >
>> > diff --git a/drivers/pci/dwc/pcie-designware-host.c b/drivers/pci/dwc/pcie-designware-host.c
>> > index 5ba3349..e43c21a 100644
>> > --- a/drivers/pci/dwc/pcie-designware-host.c
>> > +++ b/drivers/pci/dwc/pcie-designware-host.c
>> > @@ -294,16 +294,21 @@ int dw_pcie_host_init(struct pcie_port *pp)
>> >                 dev_err(dev, "missing *config* reg space\n");
>> >         }
>> >
>> > -       ret = of_pci_get_host_bridge_resources(np, 0, 0xff, &res, &pp->io_base);
>> > +       bridge = pci_alloc_host_bridge(0);
>> > +       if (!bridge)
>> > +               return  -ENOMEM;
>> > +
>>
>> I think here we warn to have the pci_alloc_host_bridge() called in the
>> individual
>> drivers, to have them allocate the dw_pcie structure as part of the host
>> bridge allocation, before calling hisi_add_pcie_port().
>
> I am almost done refactoring this series and this is the last review to
> address. What you suggest above makes sense but:
>
> 1) it means patching ALL dw_pcie_host_init() callers and allocate the
>    host bridge there, not sure it simplifies, certainly it complicates
>    the error handling path (given that the host bridge memory is
>    probably the only memory that is allocated with kzalloc instead of
>    devm interface so it needs unwinding)
>
> 2) I noticed that allocating the host bridge in the caller complicates
>    error handling, in particular code in the mainline (ie tegra and
>    ftpci100) using pci_alloc_host_bridge() needs already patching since it
>    may leak memory if PCI host bridge drivers probing fails.
>
> I can implement (1) and (2) but I wanted to ask first to understand if
> that's the direction we want to take.

Good question. Maybe we should add a devm_pci_alloc_host_bridge()
instead? Would that solve these problems without creating bigger ones?

        Arnd