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[PATCH] ppc32: Tell userland about lack of standard TB

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Glibc is about to get some new high precision timer stuff that relies on
the standard timebase of the PPC architecture.

However, some (rare & old) CPUs do not have such timebase and it is a
bit annoying to have your stuff just crash because you are running on
the wrong CPU...

This exposes to userland a CPU feature bit that tells that the current
processor doesn't have a standard timebase.  It's negative logic so that
glibc will still "just work" on older kernels (it will just be unhappy
on those old CPUs but that doesn't really matter as distro tend to
update glibc & kernel at the same time).

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Benjamin Herrenschmidt 2005-10-12 14:22:50 +10:00 committed by Linus Torvalds
parent cbd27b8ced
commit d8e998c58a
2 changed files with 4 additions and 2 deletions
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5
arch/ppc/kernel/cputable.c
View file

@ -91,7 +91,7 @@ struct cpu_spec cpu_specs[] = {
.cpu_features = CPU_FTR_COMMON | CPU_FTR_601 |
CPU_FTR_HPTE_TABLE,
.cpu_user_features = COMMON_PPC | PPC_FEATURE_601_INSTR |
PPC_FEATURE_UNIFIED_CACHE,
PPC_FEATURE_UNIFIED_CACHE | PPC_FEATURE_NO_TB,
.icache_bsize = 32,
.dcache_bsize = 32,
.cpu_setup = __setup_cpu_601
@ -745,7 +745,8 @@ struct cpu_spec cpu_specs[] = {
.cpu_name = "403GCX",
.cpu_features = CPU_FTR_SPLIT_ID_CACHE |
CPU_FTR_USE_TB,
.cpu_user_features = PPC_FEATURE_32 | PPC_FEATURE_HAS_MMU,
.cpu_user_features = PPC_FEATURE_32 |
PPC_FEATURE_HAS_MMU | PPC_FEATURE_NO_TB,
.icache_bsize = 16,
.dcache_bsize = 16,
},

1
include/asm-ppc/cputable.h
View file

@ -24,6 +24,7 @@
#define PPC_FEATURE_HAS_SPE 0x00800000
#define PPC_FEATURE_HAS_EFP_SINGLE 0x00400000
#define PPC_FEATURE_HAS_EFP_DOUBLE 0x00200000
#define PPC_FEATURE_NO_TB 0x00100000
#ifdef __KERNEL__