Re: [PATCH 2/3] PCI: of: avoid 'devm_pci_remap_iospace' if PCI_IOBASE is not defined

[Sergio Paracuellos <sergio.paracuellos@gmail.com>]

Hi Jiaxun,

On Sun, Aug 8, 2021 at 3:41 AM Jiaxun Yang <jiaxun.yang@flygoat.com> wrote:
>
>
>
> 在2021年8月7日八月 下午3:24，Sergio Paracuellos写道：
> > Defining PCI_IOBASE for MIPS ralink in expected addresses results in
> > PCI IO
> > resources being assigned but the addresses generated for IO accesses
> > are wrong
> > since the ioremap in the PCI core function
> > 'pci_parse_request_of_pci_ranges'
> > tries to remap to a fixed virtual address (PC_IOBASE) which can't work
> > for KSEG1
> > addresses. To get it working this way, we would need to put PCI_IOBASE
> > somewhere
> > into KSEG2 which will result in creating TLB entries for IO addresses,
> > which most
> > of the time isn't needed on MIPS because of access via KSEG1. To allow
>
> It was designed to allow multiple PCI bridge with sparse IO space pattern.
> So for ralink it's not going to happen?

Sorry, I don't understand your question. Can you please clarify it for me?

Thanks,
    Sergio Paracuellos
>
> Thanks.
> - Jiaxun
>
>
> > MIPS PCI
> > drivers to properly use the PCI generic core we need to increase
> > IO_SPACE_LIMIT
> > since IO addresses are in addresses higher that 0xffff. We also need to
> > avoid
> > the call 'devm_pci_remap_iospace' when
> > 'pci_parse_request_of_pci_ranges' is
> > called to avoid the following problem:
> >
> > ------------[ cut here ]------------
> > WARNING: CPU: 2 PID: 1 at ../drivers/pci/pci.c:4066 pci_remap_iospace+0x3c/0x54
> > This architecture does not support memory mapped I/O
> > Modules linked in:
> > CPU: 2 PID: 1 Comm: swapper/0 Not tainted 5.10.1+ #1228
> > Stack : 00000000 00000000 807fa974 00000000 827ffa80 80066b48 80710000 0000000b
> >         00000000 00000000 81c59aac 7d06ddec 80850000 00000001 81c59a40 7d06ddec
> >         00000000 00000000 807c909c 81c598f0 00000001 81c59904 00000000 0000000a
> >         203a6d6d 80708880 0000000f 70617773 80850000 00000000 00000000 807d0000
> >         807ffecc 1e160000 00000001 00000200 00000000 8054e920 00000008 815e0008
> >         ...
> > Call Trace:
> > [<80008efc>] show_stack+0x8c/0x130
> > [<806e1674>] dump_stack+0x9c/0xc8
> > [<80024a3c>] __warn+0xc0/0xe8
> > [<80024ad0>] warn_slowpath_fmt+0x6c/0xbc
> > [<80410ca8>] pci_remap_iospace+0x3c/0x54
> > [<80410d20>] devm_pci_remap_iospace+0x58/0xa4
> > [<8042019c>] devm_of_pci_bridge_init+0x4dc/0x55c
> > [<80408de8>] devm_pci_alloc_host_bridge+0x78/0x88
> > [<80424e44>] mt7621_pci_probe+0x68/0x9a4
> > [<80464804>] platform_drv_probe+0x40/0x7c
> > [<804628bc>] really_probe+0x2fc/0x4e4
> > [<80463214>] device_driver_attach+0x4c/0x74
> > [<80463384>] __driver_attach+0x148/0x150
> > [<8046047c>] bus_for_each_dev+0x6c/0xb0
> > [<804614dc>] bus_add_driver+0x1b4/0x1fc
> > [<80463aa0>] driver_register+0xd0/0x110
> > [<80001714>] do_one_initcall+0x84/0x1c0
> > [<808e7fd0>] kernel_init_freeable+0x214/0x24c
> > [<806e4164>] kernel_init+0x14/0x118
> > [<80003358>] ret_from_kernel_thread+0x14/0x1c
> >
> > ---[ end trace 1c9d4412bd51b53c ]---
> > mt7621-pci 1e140000.pcie: error -19: failed to map resource [io
> > 0x1e160000-0x1e16ffff]
> >
> > Hence don't call 'devm_pci_remap_iospace' if PCI_IOBASE is not defined to get
> > a working PCI core APIs for MIPS ralink platforms.
> >
> > Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
> > ---
> >  drivers/pci/of.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/pci/of.c b/drivers/pci/of.c
> > index a143b02b2dcd..657aef39bf63 100644
> > --- a/drivers/pci/of.c
> > +++ b/drivers/pci/of.c
> > @@ -564,12 +564,14 @@ static int pci_parse_request_of_pci_ranges(struct
> > device *dev,
> >
> >               switch (resource_type(res)) {
> >               case IORESOURCE_IO:
> > +#ifdef PCI_IOBASE
> >                       err = devm_pci_remap_iospace(dev, res, iobase);
> >                       if (err) {
> >                               dev_warn(dev, "error %d: failed to map resource %pR\n",
> >                                        err, res);
> >                               resource_list_destroy_entry(win);
> >                       }
> > +#endif
> >                       break;
> >               case IORESOURCE_MEM:
> >                       res_valid |= !(res->flags & IORESOURCE_PREFETCH);
> > --
> > 2.25.1
> >
> >
>
>
> --
> - Jiaxun