Re: [PATCH] PCI: tegra: Use generic accessors where possible

[Thierry Reding <thierry.reding@gmail.com>]

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On Wed, Sep 27, 2017 at 02:26:04PM +0530, vidya sagar wrote:
> On Sat, Sep 23, 2017 at 11:48 AM, Thierry Reding
> <thierry.reding@gmail.com> wrote:
> > The Tegra PCI host controller can generate configuration space accesses
> > with byte, word and dword granularity for devices. Only root ports can't
> > have their configuration space accessed in this way.
> >
> > Signed-off-by: Thierry Reding <treding@nvidia.com>
> > ---
> >  drivers/pci/host/pci-tegra.c | 24 ++++++++++++++++++++++--
> >  1 file changed, 22 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/pci/host/pci-tegra.c b/drivers/pci/host/pci-tegra.c
> > index 9c40da54f88a..e8e1ddbaabc9 100644
> > --- a/drivers/pci/host/pci-tegra.c
> > +++ b/drivers/pci/host/pci-tegra.c
> > @@ -491,12 +491,32 @@ static void __iomem *tegra_pcie_map_bus(struct pci_bus *bus,
> >         return addr;
> >  }
> >
> > +static int tegra_pcie_config_read(struct pci_bus *bus, unsigned int devfn,
> > +                                 int where, int size, u32 *value)
> > +{
> > +       if (bus->number == 0)
> > +               return pci_generic_config_read32(bus, devfn, where, size,
> > +                                                value);
> > +
> > +       return pci_generic_config_read(bus, devfn, where, size, value);
> 
> Since T20, T30 and T124 had issues with 8-bit and 16-bit end point
> config accesses, generic accessors should be used only for T210

I thought that 8-bit and 16-bit configuration space accesses were only
ever problematic for the root ports. I've certainly not seen 8-bit and
16-bit accesses fail on any of the devices I tested on. That is, this
patch was tested on TrimSlice (Tegra20), Beaver (Tegra30), Jetson TK1
(Tegra124) and Jetson TX1 (Tegra210) without any issues.

Thierry

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