Date: Sun, 26 Jun 2016 16:22:41 -0700 From: Mark Millard <markmi@dsl-only.net> To: FreeBSD PowerPC ML <freebsd-ppc@freebsd.org> Subject: Re: svn commit: r302214 - head/sys/powerpc/aim [my PowerMac G5 testing delayed] Message-ID: <B2997643-4FB3-43AF-8942-61E6E4DB2ACF@dsl-only.net>
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Quoting: > Author: nwhitehorn > Date: Sun Jun 26 18:43:42 2016 > New Revision: 302214 > URL: > https://svnweb.freebsd.org/changeset/base/302214 > > > Log: > Enter 64-bit mode as early as possible in the 64-bit PowerPC boot sequence. > Most of the effect of setting MSR[SF] is that the CPU will stop ignoring > the high 32 bits of registers containing addresses in load/store > instructions. As such, the kernel was setting it only when it began to > need access to high memory. MSR[SF] also affects the operation of some > conditional instructions, however, and so setting it at late times could > subtly break code at very early times. This fixes use of the FDT mode in > loader, and FDT boot more generally, on 64-bit PowerPC systems. > > Hardware provided by: IBM LTC > Approved by: re (kib) > > Modified: > head/sys/powerpc/aim/aim_machdep.c > head/sys/powerpc/aim/locore64.S Usually I would test a couple of powerpc64 capable PowerMacs (a so-called "Quad Core" one and a Dual Processor, single core per processor, one) for if this changes the boot behavior noticeably for them. But it will likely be a couple of months or more before I again have access to them. Hopefully others will happen to test such examples before then. Context note for PowerMacs used under powerpc64 FreeBSD: When I boot a powerpc64 PowerMac with a FreeBSD for powerpc64 I normally run with a personal PowerMac specific change to allow reliable booting, even when there is lots of RAM (8G, 12G, or 16G). The change is tied to the transitions into and out of Apple's OpenFirmware and I observed it to avoid memory trashing that I had observed otherwise. When I made this change I effectively eliminated just one instruction from ofw_sprg_prepare(void): I went for the smallest generated-code change that made the booting reliable on the PowerMac's that I commonly have access to. The below just eliminates the pair: "mtsprg0 %1\n\t" and "r"(ofmsr[1]), # svnlite diff /usr/src/sys/powerpc/ofw/ofw_machdep.c Index: /usr/src/sys/powerpc/ofw/ofw_machdep.c =================================================================== --- /usr/src/sys/powerpc/ofw/ofw_machdep.c (revision 302180) +++ /usr/src/sys/powerpc/ofw/ofw_machdep.c (working copy) @@ -111,6 +111,24 @@ * Assume that interrupt are disabled at this point, or * SPRG1-3 could be trashed */ +#if defined(AIM) && defined(__powerpc64__) +/* HACK: PowerMac G5 specific code to avoid demonstrated hangs in + * the early boot time frame: avoid mtsprg0 use. + * This would need a live test for PowerMac vs. not in order + * to remove HACK status --but without calling into + * OpenFirmware or the problem would be recreated. + */ + if (1) + __asm __volatile("mfsprg0 %0\n\t" + "mtsprg1 %1\n\t" + "mtsprg2 %2\n\t" + "mtsprg3 %3\n\t" + : "=&r"(ofw_sprg0_save) + : "r"(ofmsr[2]), + "r"(ofmsr[3]), + "r"(ofmsr[4])); + else +#endif __asm __volatile("mfsprg0 %0\n\t" "mtsprg0 %1\n\t" "mtsprg1 %2\n\t" I did not change the mfsprg0 nor did I change ofw_sprg_restore(void): the booting was reliable without any change for those. [I do have access to my sources even though I do not have access to the PowerMacs for a while.] === Mark Millard markmi at dsl-only.nethelp
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