powerpc fixes for 5.19 #6

- Re-enable the new amdgpu display engine for powerpc, as long as the compiler is
    correctly configured.
 
  - Disable stack variable initialisation in prom_init to fix GCC 12 allmodconfig.
 
 Thanks to: Dan Horák, Sudip Mukherjee.
 -----BEGIN PGP SIGNATURE-----
 
 iQJHBAABCAAxFiEEJFGtCPCthwEv2Y/bUevqPMjhpYAFAmLjzzUTHG1wZUBlbGxl
 cm1hbi5pZC5hdQAKCRBR6+o8yOGlgI9HD/kBUx+GUGmv/q72tG99fGeyTFWzdBoQ
 sUbgzPl74Oanf+vp4q150PfL+pka1/Cajl+2xxZOAg6IFrerY6HW3xu1wOQdR01b
 imTujF/Tb1PoQKuSuUQ0elFPKw2h6PpOl65Z+XF+/tAoKG4IHakhVc9jjRLNZQmL
 tKAaWpR2yLHyIai1DrEzwy/J0oeXRzEbJqz4zRb3gicZusiI3bTLDqkS/U1Pg04M
 t/sfe1FFFbgjMX9Rogjt9A+k/qMISJTLcm06R9+6L4XQrdnrio5ITSO5GFdJHYlv
 0Ej0BthkPaUkxrZB5qfz1h7+ZLHLgRXDVNHbM2FvvATeuOzyCsZDIjw6lxJdN8l2
 hWXrkWEYJM4tBpn+sfMdgiOVBZExz6UEz28/0sFxTEq1CFQU+m00hevXLnQpLwFp
 X3T3PR1LTvCMsbbNDF98yfKiAB41fa59xw1ZIizItuPBHjUHjPctYM94BTYRmsVI
 WGTGSDjgxnn+5u4VD9QN05ADTjEJtOGHZNZX9KeuyhMKEnKYunipFP4kyJWXTMkP
 06S1fgfN4d1FOyQSsRnvLV7ZMo+/nD0gwNFUniINTYKb8TXyogWaMNUvHqfrdBrd
 Af8oObRj0oJ7Qrq5z+MzL2Vx9PlkMIBIb3tj/QBo3nFvnkG404w+HyxANnF3id1v
 03pWRaTJJemicw==
 =u93i
 -----END PGP SIGNATURE-----

Merge tag 'powerpc-5.19-6' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

Pull powerpc fixes from Michael Ellerman:

 - Re-enable the new amdgpu display engine for powerpc, as long as the
   compiler is correctly configured.

 - Disable stack variable initialisation in prom_init to fix GCC 12
   allmodconfig.

Thanks to Dan Horák and Sudip Mukherjee.

* tag 'powerpc-5.19-6' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  drm/amdgpu: Re-enable DCN for 64-bit powerpc
  powerpc/64s: Disable stack variable initialisation for prom_init

arch/powerpc/Kconfig

@@ -282,6 +282,10 @@ config PPC
 	# Please keep this list sorted alphabetically.
 	#
 
+config PPC_LONG_DOUBLE_128
+	depends on PPC64
+	def_bool $(success,test "$(shell,echo __LONG_DOUBLE_128__ | $(CC) -E -P -)" = 1)
+
 config PPC_BARRIER_NOSPEC
 	bool
 	default y

arch/powerpc/kernel/Makefile

@@ -20,6 +20,7 @@ CFLAGS_prom.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
 CFLAGS_prom_init.o += -fno-stack-protector
 CFLAGS_prom_init.o += -DDISABLE_BRANCH_PROFILING
 CFLAGS_prom_init.o += -ffreestanding
+CFLAGS_prom_init.o += $(call cc-option, -ftrivial-auto-var-init=uninitialized)
 
 ifdef CONFIG_FUNCTION_TRACER
 # Do not trace early boot code

drivers/gpu/drm/amd/display/Kconfig

@@ -6,7 +6,7 @@ config DRM_AMD_DC
 	bool "AMD DC - Enable new display engine"
 	default y
 	select SND_HDA_COMPONENT if SND_HDA_CORE
-	select DRM_AMD_DC_DCN if X86 && !(KCOV_INSTRUMENT_ALL && KCOV_ENABLE_COMPARISONS)
+	select DRM_AMD_DC_DCN if (X86 || PPC_LONG_DOUBLE_128) && !(KCOV_INSTRUMENT_ALL && KCOV_ENABLE_COMPARISONS)
 	help
 	  Choose this option if you want to use the new display engine
 	  support for AMDGPU. This adds required support for Vega and