Re: [PATCH v2 1/3] MIPS: ralink: Define PCI_IOBASE

[Thomas Bogendoerfer <tsbogend@alpha.franken.de>]

On Thu, Jul 29, 2021 at 01:21:45PM +0200, Sergio Paracuellos wrote:
> Hi Thomas,
> 
> On Thu, Jul 29, 2021 at 12:02 PM Thomas Bogendoerfer
> <tsbogend@alpha.franken.de> wrote:
> >
> > On Mon, Jun 14, 2021 at 12:06:15PM +0200, Sergio Paracuellos wrote:
> > > PCI_IOBASE is used to create VM maps for PCI I/O ports, it is
> > > required by generic PCI drivers to make memory mapped I/O range
> > > work. Hence define it for ralink architectures to be able to
> > > avoid parsing manually IO ranges in PCI generic driver code.
> > > Function 'plat_mem_setup' for ralink is using 'set_io_port_base'
> > > call using '0xa0000000' as address, so use the same address in
> > > the definition to align things.
> > >
> > > Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
> > > ---
> > >  arch/mips/include/asm/mach-ralink/spaces.h | 10 ++++++++++
> > >  1 file changed, 10 insertions(+)
> > >  create mode 100644 arch/mips/include/asm/mach-ralink/spaces.h
> > >
> > > diff --git a/arch/mips/include/asm/mach-ralink/spaces.h b/arch/mips/include/asm/mach-ralink/spaces.h
> > > new file mode 100644
> > > index 000000000000..87d085c9ad61
> > > --- /dev/null
> > > +++ b/arch/mips/include/asm/mach-ralink/spaces.h
> > > @@ -0,0 +1,10 @@
> > > +/* SPDX-License-Identifier: GPL-2.0 */
> > > +#ifndef __ASM_MACH_RALINK_SPACES_H_
> > > +#define __ASM_MACH_RALINK_SPACES_H_
> > > +
> > > +#define PCI_IOBASE   _AC(0xa0000000, UL)
> > > +#define PCI_IOSIZE   SZ_16M
> > > +#define IO_SPACE_LIMIT       (PCI_IOSIZE - 1)
> > > +
> > > +#include <asm/mach-generic/spaces.h>
> > > +#endif
> >
> > does this really work for you ? I tried the same trick for RB532
> > and the generated IO addresses are wrong...
> 
> I got pci io resources assigned without complaints from the pci core
> code. I don't have real pci card that uses I/O bars but this is what I
> see in the boot (I added some traces when I was testing this):

resource handling works, but the addresses generated for IO access
are wrong, because the iomap tries to ioremap it to a fixed
virtual address (PCI_IOBASE), which can't work for KSEG1 addresses.

> Is this wrong?

to get it working this way, we would need to put PCI_IOBASE somewhere
into KSEG2, which I don't like since it will create TLB entries for IO
addresses, which most of the time isn't needed on MIPS because of
access via KSEG1.

I'd much prefer to make the devm_pci_remap_iospace() in drivers/pci/of.c
optional. Something like this

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);


This together with an increased IO space via

#define IO_SPACE_LIMIT 0x1fffffff

gives me a working PCI bus on the RB532.

No idea, if the patch would be accepted by the PCI maintainers.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]