[PATCH RESEND 1/1] drm/amd/display: add DCN support for ARM64

[Ao Zhong]

Am Do., 27. Okt. 2022 um 12:52 Uhr schrieb Arnd Bergmann <arnd at arndb.de>:
>
> On Thu, Oct 27, 2022, at 02:25, Ao Zhong wrote:
> > After moving all FPU code to the DML folder, we can enable DCN support
> > for the ARM64 platform. Remove the -mgeneral-regs-only CFLAG from the
> > code in the DML folder that needs to use hardware FPU, and add a control
> > mechanism for ARM Neon.
> >
> > Signed-off-by: Ao Zhong <hacc1225 at gmail.com>
>
> There have been problems with stack frame overflows on this code
> in the past, how much have you tested this with random configurations
> to see if we still hit them in corner cases on arm64 that may not
> show up on x86 or powerpc? I would expect to see a few more of them
> for every new architecture port.

I just used this patch on my own Desktop and didn't test it much.

> > index d0c6cf61c676..3cdd109189e0 100644
> > --- a/drivers/gpu/drm/amd/display/dc/dml/Makefile
> > +++ b/drivers/gpu/drm/amd/display/dc/dml/Makefile
> > @@ -33,6 +33,12 @@ ifdef CONFIG_PPC64
> >  dml_ccflags := -mhard-float -maltivec
> >  endif
> >
> > +ifdef CONFIG_ARM64
> > +ifdef CONFIG_DRM_AMD_DC_DCN
> > +dml_rcflags_arm64 := -mgeneral-regs-only
> > +endif
> > +endif
> > +
>
> >  CFLAGS_$(AMDDALPATH)/dc/dml/calcs/dcn_calcs.o := $(dml_ccflags)
> >  CFLAGS_$(AMDDALPATH)/dc/dml/calcs/dcn_calc_auto.o := $(dml_ccflags)
> >  CFLAGS_$(AMDDALPATH)/dc/dml/calcs/dcn_calc_math.o := $(dml_ccflags)
> > -Wno-tautological-compare
> > -CFLAGS_REMOVE_$(AMDDALPATH)/dc/dml/display_mode_vba.o := $(dml_rcflags)
> > +CFLAGS_REMOVE_$(AMDDALPATH)/dc/dml/display_mode_vba.o :=
> > $(dml_rcflags) $(dml_rcflags_arm64)
>
> Why do you need separate $(dml_rcflags) and $(dml_rcflags_arm64)
> rather than adding -mgeneral-regs-only to $(dml_rcflags) directly?
>
>     Arnd

I don't know if $(dml_rcflags) has any other use. I'm afraid my patch
will break something.