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Date:      Tue, 20 Sep 2016 23:46:51 -0700
From:      Mark Millard <markmi@dsl-only.net>
To:        Justin Hibbits <chmeeedalf@gmail.com>, Nathan Whitehorn <nwhitehorn@freebsd.org>
Cc:        FreeBSD PowerPC ML <freebsd-ppc@freebsd.org>, svn-src-head@freebsd.org
Subject:   svn commit: r306065 - in head/sys vs. PowerMacs: Nathan's trail patch included but inappropriate?
Message-ID:  <C48933C3-DB22-4D94-B22D-B51822197E4E@dsl-only.net>

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The following from

=
https://lists.freebsd.org/pipermail/svn-src-head/2016-September/091934.htm=
l

seems in include a patch that Nathan made for testing on =
PowerMac/iMac/Xserve G5's that failed the PowerMac7,3 test that was =
tried by Jukka A. Ukkonen.

> Modified: head/sys/powerpc/ofw/ofw_machdep.c
> =
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D
> --- head/sys/powerpc/ofw/ofw_machdep.c	Wed Sep 21 02:27:23 2016	=
(r306064)
> +++ head/sys/powerpc/ofw/ofw_machdep.c	Wed Sep 21 02:28:39 2016	=
(r306065)
> @@ -99,6 +99,7 @@ ofw_restore_trap_vec(char *restore_trap_
>  /*
>   * Saved SPRG0-3 from OpenFirmware. Will be restored prior to the =
callback.
>   */
> +#ifndef __powerpc64__
>  register_t	ofw_sprg0_save;
> =20
>  static __inline void
> @@ -140,6 +141,8 @@ ofw_sprg_restore(void)
>  }
>  #endif
> =20
> +#endif
> +
>  static int
>  parse_ofw_memory(phandle_t node, const char *prop, struct mem_region =
*output)
>  {
> @@ -344,11 +347,12 @@ OF_initial_setup(void *fdt_ptr, void *ju
>  	ofmsr[0] =3D mfmsr();
>  	#ifdef __powerpc64__
>  	ofmsr[0] &=3D ~PSL_SF;
> -	#endif
> +	#else
>  	__asm __volatile("mfsprg0 %0" : "=3D&r"(ofmsr[1]));
>  	__asm __volatile("mfsprg1 %0" : "=3D&r"(ofmsr[2]));
>  	__asm __volatile("mfsprg2 %0" : "=3D&r"(ofmsr[3]));
>  	__asm __volatile("mfsprg3 %0" : "=3D&r"(ofmsr[4]));
> +	#endif
>  	openfirmware_entry =3D openfirm;
> =20
>  	if (ofmsr[0] & PSL_DR)
> @@ -440,7 +444,9 @@ openfirmware_core(void *args)
>  	 */
>  	oldmsr =3D intr_disable();
> =20
> +#ifndef __powerpc64__
>  	ofw_sprg_prepare();
> +#endif
> =20
>  	/* Save trap vectors */
>  	ofw_save_trap_vec(save_trap_of);
> @@ -463,7 +469,9 @@ openfirmware_core(void *args)
>  	/* Restore trap vecotrs */
>  	ofw_restore_trap_vec(save_trap_of);
> =20
> +#ifndef __powerpc64__
>  	ofw_sprg_restore();
> +#endif
> =20
>  	intr_restore(oldmsr);

Part of the ofw_sprg_prepare() and ofw_sprg_restore() activity is =
required for PowerMac G5's to boot: the save of the FreeBSD sprg0 value =
and its later restore back to sprg0. (Established by other testing after =
Nathan's patch was tried.)

My guess is that this code was accidentally included in -r306065, not =
intentionally included.


[There is the separate issue that avoiding restoring the Open Firmware =
sprg0 value before calling into Open Firmware (leaving the FreeBSD value =
in place) helps PowerMac G5's boot more reliably by allowing correct =
handling some SLB faults that sometimes occur.]

=3D=3D=3D
Mark Millard
markmi at dsl-only.net




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