Re: [PATCH v4 1/4] video: fbdev: atyfb: only use ioremap_uc() on i386 and ia64

[Helge Deller]

On 3/8/23 22:34, Arnd Bergmann wrote:
> 0On Wed, Mar 8, 2023, at 21:01, Luis Chamberlain wrote:
> > On Wed, Mar 08, 2023 at 09:07:07PM +0800, Baoquan He wrote:
> > > From: Arnd Bergmann <arnd@xxxxxxxx>
> > >
> > > ioremap_uc() is only meaningful on old x86-32 systems with the PAT
> > > extension, and on ia64 with its slightly unconventional ioremap()
> > > behavior, everywhere else this is the same as ioremap() anyway.
> > >
> > > Change the only driver that still references ioremap_uc() to only do so
> > > on x86-32/ia64 in order to allow removing that interface at some
> > > point in the future for the other architectures.
> > >
> > > On some architectures, ioremap_uc() just returns NULL, changing
> > > the driver to call ioremap() means that they now have a chance
> > > of working correctly.
> > >
> > > Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> > > Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
> > > Cc: Helge Deller <deller@xxxxxx>
> > > Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
> > > Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
> > > Cc: linux-fbdev@xxxxxxxxxxxxxxx
> > > Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> >
> > Reviewed-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
> >
> > Is anyone using this driver these days? How often do fbdev drivers get
> > audited to see what can be nuked?
>
> Geert already mentioned that this one is likely used on old
> powermac systems.

and the latest generation of parisc machines use it too.

In addition, on parisc machines it's also important to map all io-space
memory uncacheable. Since ioremap() takes care of it anyway, the ioremap_uc()
was simply referencing the call to ioremap().

Helge

> I think my arm boardfile removal orphaned
> some other fbdev drivers though. I removed the ones that can
> no longer be enabled, but think a bunch of other ones
> are still selectable but have no platform_device definition
> or DT support: FB_PXA168, FB_DA8XX, FB_MX3, and MMP_FB.
>
> These four platforms are all still supported with DT, but
> over time it gets less likely that anyone is still interested
> in adding DT support to the fbdev drivers.
>
>      Arnd