Date: Sun, 20 Dec 2015 10:45:25 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 205458] 11.0-CURRENT/10-STABLE powerpc64: a PowerMac G5 specific sys/powerpc/ofw/ofw_machdep.c change for reliable PowerMac G5 booting (with lots of RAM) Message-ID: <bug-205458-8@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=205458 Bug ID: 205458 Summary: 11.0-CURRENT/10-STABLE powerpc64: a PowerMac G5 specific sys/powerpc/ofw/ofw_machdep.c change for reliable PowerMac G5 booting (with lots of RAM) Product: Base System Version: 11.0-CURRENT Hardware: ppc OS: Any Status: New Severity: Affects Only Me Priority: --- Component: kern Assignee: freebsd-bugs@FreeBSD.org Reporter: markmi@dsl-only.net The standard GENERIC64 powerpc64 FreeBSD builds do not reliably boot PowerMac G5's: hang ups in the very early boot activity happen frequently but randomly. 11.0, 10.x, and far into the past are all this way as I understand. I have experience with 10.0-RELEASE to 11.0-CURRENT. I have been testing a PowerMac G5 specific change since late 2015-Feb or so and have reliable booting with the change and horribly unreliable booting without it. The G5's in question happen to have lots of RAM for their vintage (8GB, 12GB, 16GB). (It took months and thousands of reboot attempts to isolate the change, the more RAM the worse the failure rate for booting in my testing.) The change is in ofw_sprg_prepare of sys/powerpc/ofw/ofw_machdep.c and could look something like (presented in a form to show new/PowerMacG5-Specific code and old general code): #ifdef POWERMAC_G5_SPECIFIC_BUILD __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 // The historical code: __asm __volatile("mfsprg0 %0\n\t" "mtsprg0 %1\n\t" "mtsprg1 %2\n\t" "mtsprg2 %3\n\t" "mtsprg3 %4\n\t" : "=&r"(ofw_sprg0_save) : "r"(ofmsr[1]), "r"(ofmsr[2]), "r"(ofmsr[3]), "r"(ofmsr[4])); #endif In other words: for PowerMac G5's omit the mtsprg0 from ofmsr[1]: leave the register as it already is instead of resetting it. The value in ofmsr[1] is inappropriate to the context. I deliberately kept the change minimal and left in all other code related to the register. Unfortunately I do not know how to accurately detect a PowerMac G5 context while avoiding calling into openfirmware. So I do not know how to make this have an auto-adjusting/dynamic check for a PowerMac G5. Entering openfirmware first would likely recreate the problem (or other problems) from what I can tell. If appropriate FreeBSD folks consider PowerMac G5's still to be worth-the-effort as tier2 examples to support a predefined, systematic way to buildkernel for reliable PowerMac G5 booting then some sort of publically-documented technique of configuring a build to control the distinction would be appropriate. But it might be that there is a policy of "no such platform-specific source code for desktop machines". Understandable if so. There might be conventions for handling such contexts that I'm not aware of. I've been testing/using various vintages of 11.0-CURRENT, 10.x-RELENG, and 10-STABLE, progressing over time. All have been reliably booting with the change on all 3 PowerMac G5's that I have access to. (I have no other powerpc64 context.) -- You are receiving this mail because: You are the assignee for the bug.
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