On Sat, 2017-08-05 at 12:52 +0800, Ryder Lee wrote:
> Hi Honghui, Bjorn,
>
> On Fri, 2017-08-04 at 08:18 -0500, Bjorn Helgaas wrote:
> > On Fri, Aug 04, 2017 at 04:39:36PM +0800, Honghui Zhang wrote:
> > > On Thu, 2017-08-03 at 17:42 -0500, Bjorn Helgaas wrote:
> > > > > +
> > > > > +static struct mtk_pcie_port *mtk_pcie_find_port(struct mtk_pcie *pcie,
> > > > > + struct pci_bus *bus, int devfn)
> > > > > +{
> > > > > + struct pci_dev *dev;
> > > > > + struct pci_bus *pbus;
> > > > > + struct mtk_pcie_port *port, *tmp;
> > > > > +
> > > > > + list_for_each_entry_safe(port, tmp, &pcie->ports, list) {
> > > > > + if (bus->number == 0 && port->index == PCI_SLOT(devfn)) {
> > > > > + return port;
> > > > > + } else if (bus->number != 0) {
> > > > > + pbus = bus;
> > > > > + do {
> > > > > + dev = pbus->self;
> > > > > + if (port->index == PCI_SLOT(dev->devfn))
> > > > > + return port;
> > > > > + pbus = dev->bus;
> > > > > + } while (dev->bus->number != 0);
> > > > > + }
> > > > > + }
> > > > > +
> > > > > + return NULL;
> > > >
> > > > You should be able to use sysdata to avoid searching the list.
> > > > See drivers/pci/host/pci-aardvark.c, for example.
> > > >
> > >
> > > I could put the mtk_pcie * in sysdata, but still need to searching the
> > > list to get the mtk_pcie_port *, how about:
> > >
> > > list_for_each_entry_safe(port, tmp, &pcie->ports, list) {
> > > if (port->index == PCI_SLOT(devfn))
> > > return port;
> > > }
> >
> > No. Other drivers don't need to search the list. Please take a look
> > at them and see how they solve this problem. I don't think your
> > hardware is fundamentally different in a way that means you need to
> > search when the others don't.
> >
>
> I'm not directly involved in this generation, but I guess the main reason why Honghui need to do that is just because this hardware access configuration space via per-port registers, not just for the guard.
> Currently, We had a host bridge with two ports (two subnodes in binding text), thus he tried to tells them apart so that he can get the correct registers.
>
> Some platforms don't need to do that since they just have a single port (no more subnodes), the others might have specific/shared registers to access configuration space. (e.g. Tegra, MTK legacy IP block).
> Or, he can split them into two independent nodes, but it will break common probing flow by doing so. (I'd prefer to use subnodes.)
>
> Ryder
>
Sorry for the typesetting in previous mail and noise again,
I've took a look at pci-rcar-gen2.c, this is a similar case I can found
for Honghui's case. It gathers two ports reg regions into one, and uses
the "slot id" to calculate the cfg base of each port.
Perhaps this is a example for those who need to use subnodes and use
port registers for cfg operation. Not sure whether it's worthwhile doing
that since we need to changes ports/host structures.
Ryder.
