linux-kernel - Re: [PATCH 5/6] MIPS: implement architecture dependent 'pci_remap

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Date:   Sat, 25 Sep 2021 20:08:58 +0200
From:   Sergio Paracuellos <sergio.paracuellos@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Rob Herring <robh@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Liviu Dudau <Liviu.Dudau@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        gregkh <gregkh@...uxfoundation.org>,
        "open list:BROADCOM NVRAM DRIVER" <linux-mips@...r.kernel.org>,
        linux-pci <linux-pci@...r.kernel.org>,
        linux-staging@...ts.linux.dev, NeilBrown <neil@...wn.name>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/6] MIPS: implement architecture dependent 'pci_remap_iospace()'

Hi Arnd,

On Sat, Sep 25, 2021 at 7:32 PM Arnd Bergmann <arnd@...db.de> wrote:
>
> On Fri, Sep 24, 2021 at 11:11 PM Sergio Paracuellos
> <sergio.paracuellos@...il.com> wrote:
> >
> > To make PCI IO work we need to properly virtually map IO cpu physical address
> > and set this virtual address as the address of the first PCI IO port which
> > is set using function 'set_io_port_base()'.
> >
> > Signed-off-by: Sergio Paracuellos <sergio.paracuellos@...il.com>
>
> Acked-by: Arnd Bergmann <arnd@...db.de>

Thanks!

>
> > +int pci_remap_iospace(const struct resource *res, phys_addr_t phys_addr)
> > +{
> > +       size_t size = (res->end - res->start) + 1;
> > +       unsigned long vaddr = (unsigned long)ioremap(phys_addr, size);
> > +
> > +       set_io_port_base(vaddr);
> > +       return 0;
> > +}
>
> It might be good to check that res->start is zero here, otherwise
> the io_port_base would be off. That could happen if you ever have more
> than one bridge.

Do you mean something like the following?

int pci_remap_iospace(const struct resource *res, phys_addr_t phys_addr)
{
    unsigned long vaddr;
    size_t size;

    if (res->start != 0) {
         // Should I WARN_ONCE or just show an error/warning message??
         WARN_ONCE(1, "resource start must be zero\n");
         return -ENODEV;
   }

     size = (res->end - res->start) + 1;
     vaddr = (unsigned long)ioremap(phys_addr, size);
     return 0;
}

Thanks,
    Sergio Paracuellos
>
>         Arnd