Re: [PATCH 29/38] powerpc: Move 32-bit probe() machine to later in the boot process
From: Gerhard Pircher <hidden>
Date: 2016-06-27 20:47:43
Am 2016-06-27 um 13:29 schrieb Benjamin Herrenschmidt:
This converts all the 32-bit platforms to use the expanded device-tree which is a pretty mechanical change. Unlike 64-bit, the 32-bit kernel didn't rely on platform initializations to setup the MMU since it sets it up entirely before probe_machine() so the move has comparatively less consequences though it's a bigger patch. Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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quoted hunk ↗ jump to hunk
diff --git a/arch/powerpc/platforms/amigaone/setup.c b/arch/powerpc/platforms/amigaone/setup.c index 2fe1204..a030d3b 100644 --- a/arch/powerpc/platforms/amigaone/setup.c +++ b/arch/powerpc/platforms/amigaone/setup.c@@ -143,9 +143,7 @@ void amigaone_restart(char *cmd) static int __init amigaone_probe(void) { - unsigned long root = of_get_flat_dt_root(); - - if (of_flat_dt_is_compatible(root, "eyetech,amigaone")) { + if (of_machine_is_compatible("eyetech,amigaone")) { /* * Coherent memory access cause complete system lockup! Thus * disable this CPU feature, even if the CPU needs it.
This patch series reminds me of a long-standing issue with the AmigaOne platform code, which would have to clear the coherence (M) flag for every memory mapping to avoid lockups (especially on G4 CPUs) - as you can read in the comment below your patch above. Now the follow-up code in amigaone/setup.c to clear the corresponding CPU feature flag is essentially dead code (it used to work with a second call of do_feature_fixups() before the handling of the CPU_FTR_NEED_COHERENT flag was changed/inverted somewhere around v2.6.30). Also it doesn't seem to fix all deadlocks, as e.g. KVM virtual machines can still inject memory mappings with the M flag set AFAICT. Now I wonder, if there is a reasonably clean way to clear the M flag in all hardware page table and BAT entries without defacing generic kernel code too much. Any ideas? BR, Gerhard