ppc32: Tell userland about lack of standard TB
PATCH 1/1 ppc32: Tell userland about lack of standard TB
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).
Might still be worth getting into 2.6.14 ...
Signed-off-by Benjamin Herrenschmidt <[email protected]>
arch/ppc/kernel/cputable.c +3 -2
@@ -91,7 +91,7 @@ .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
@@ -759,7 +759,8 @@ .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, },
include/asm-ppc/cputable.h +1 -0
@@ -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__