[U-Boot] [PATCH v2 3/5] dm: ns16550: Don't map_physmem for I/O ports

[Paul Burton]

On Tue, May 17, 2016 at 06:11:22AM -0600, Simon Glass wrote:
> Hi Paul,
> 
> On 16 May 2016 at 11:44, Paul Burton <paul.burton at imgtec.com> wrote:
> > If the UART is to be accessed using I/O port accessors (inb & outb) then
> > using map_physmem doesn't make sense, since it operates in a different
> > memory space. Remove the call to map_physmem when
> > CONFIG_SYS_NS16550_PORT_MAPPED is defined, allowing I/O port addresses
> > to not be mangled by the incorrect mapping.
> >
> > Signed-off-by: Paul Burton <paul.burton at imgtec.com>
> > ---
> >
> > Changes in v2:
> > - New patch, part of a simplified approach tackling only a single Malta UART.
> >
> >  drivers/serial/ns16550.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> >
> > diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c
> > index 28da9dd..e58e6aa 100644
> > --- a/drivers/serial/ns16550.c
> > +++ b/drivers/serial/ns16550.c
> > @@ -100,7 +100,11 @@ static void ns16550_writeb(NS16550_t port, int offset, int value)
> >         unsigned char *addr;
> >
> >         offset *= 1 << plat->reg_shift;
> > +#ifdef CONFIG_SYS_NS16550_PORT_MAPPED
> > +       addr = (unsigned char *)plat->base + offset;
> > +#else
> >         addr = map_physmem(plat->base, 0, MAP_NOCACHE) + offset;
> > +#endif
> 
> Please don't add CONFIG #ifdefs in these functions. Perhaps it needs
> to be another parameter? Possibly a flag. But with driver-model we
> need to be able to support both options in the core code.

Hi Simon,

Are you sure systems rely on using I/O ports with map_physmem? The only
other systems that define CONFIG_SYS_NS16550_PORT_MAPPED are x86 ones,
in include/configs/x86-common.h, and so far as I can tell they don't use
device model which suggests this code has simply been untested before. I
don't see why you would use map_physmem on an I/O port address that is
then going to be passed to inb/outb & I think the code here is simply
wrong to do so.

> This driver is a real mess. I'm hoping we can simplify it once we have
> everything on driver model.

Agreed, that would be wonderful.

Thanks,
    Paul