Re: FOR COMMENT: void __iomem * and similar casts are Bad News

[Tony Lindgren <tony@atomide.com>]

* Russell King - ARM Linux <linux@arm.linux.org.uk> [080904 09:13]:
> On Thu, Sep 04, 2008 at 09:10:34AM -0700, Tony Lindgren wrote:
> > * Russell King - ARM Linux <linux@arm.linux.org.uk> [080904 02:47]:
> > > On Wed, Sep 03, 2008 at 11:33:51AM -0400, Eduardo Valentin wrote:
> > > > > @@ -159,7 +159,7 @@ static struct omap_mcbsp_platform_data omap730_mcbsp_pdata[] = {
> > > > >  #ifdef CONFIG_ARCH_OMAP15XX
> > > > >  static struct omap_mcbsp_platform_data omap15xx_mcbsp_pdata[] = {
> > > > >        {
> > > > > -               .virt_base      = OMAP1510_MCBSP1_BASE,
> > > > > +               .virt_base      = OMAP1510_MCBSP1_BASE, /* FIXME: virtual or physical */
> > > > AFAIK, OMAP1510_MCBSP1_BASE is physical. So, I'd say:
> > > > +               .virt_base      = IO_ADDRESS(OMAP1510_MCBSP1_BASE),
> > > > 
> > > > Because, plat-omap/mcbsp.c expect .virt_base to be a virtual address.
> > > 
> > > And today, the story is completely different, having looked through more
> > > of the code and some documentation.
> > > 
> > > - OMAPxxxx_MCBSPx_BASE are all physical addresses.  Fine.
> > > - physical addresses > 0xfffb0000 are subject to an offset (IO_OFFSET)
> > >   but others for the DSP located and DSP shared peripherals aren't.
> > > 
> > > So, applying the IO_OFFSET via IO_ADDRESS() or io_p2v() to all addresses
> > > breaks.  Meaning it's completely random whether something should be put
> > > through IO_ADDRESS() and similar.
> > > 
> > > This isn't obvious.  It isn't readable.  It isn't maintainable.  It doesn't
> > > lend itself to compile time checking.
> > 
> > Ouch. Looking at the history of the mcbsp.c the MCBSPX_BASE defines have
> > been a mix of virt and phys addresses to start with.
> > 
> > Looks like in the short term we need to define both virt_base and phys_base
> > for omap_mcbsp_platform_data.
> > 
> > Then define __arch_ioremap that understands also the DSP mappings and get
> > rid of the remaining hardcoded virtual DSP defines.
> > 
> > At that point we can also remove the virt_base from omap_mcbsp_platform_data.
> 
> Already done. ;)

That was fast :) Sounds we'll have a patch to test soon.

Tony