| Message ID | 1375046048-25853-1-git-send-email-robherring2@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Rob, On Sun, Jul 28, 2013 at 10:14:08PM +0100, Rob Herring wrote: > From: Rob Herring <rob.herring@calxeda.com> > > The work-around for A15 errata 798181 is not needed if appropriate ECO > fixes have been applied to r3p2 and earlier core revisions. This can be > checked by reading REVIDR register bits 4 and 9. If only bit 4 is set, > then the IPI broadcast can be skipped. > > Signed-off-by: Rob Herring <rob.herring@calxeda.com> > --- > v2: > - Determine the work-around needed and save in a static varible instead > of re-reading the ID registers. > > arch/arm/include/asm/cputype.h | 1 + > arch/arm/kernel/smp_tlb.c | 31 +++++++++++++++++++++++-------- > 2 files changed, 24 insertions(+), 8 deletions(-) > > diff --git a/arch/arm/include/asm/cputype.h b/arch/arm/include/asm/cputype.h > index 8c25dc4..e5952b7 100644 > --- a/arch/arm/include/asm/cputype.h > +++ b/arch/arm/include/asm/cputype.h > @@ -10,6 +10,7 @@ > #define CPUID_TLBTYPE 3 > #define CPUID_MPUIR 4 > #define CPUID_MPIDR 5 > +#define CPUID_REVIDR 6 > > #ifdef CONFIG_CPU_V7M > #define CPUID_EXT_PFR0 0x40 > diff --git a/arch/arm/kernel/smp_tlb.c b/arch/arm/kernel/smp_tlb.c > index a98b62d..da20db1 100644 > --- a/arch/arm/kernel/smp_tlb.c > +++ b/arch/arm/kernel/smp_tlb.c > @@ -73,12 +73,29 @@ static inline void ipi_flush_bp_all(void *ignored) > #ifdef CONFIG_ARM_ERRATA_798181 > static int erratum_a15_798181(void) > { > - unsigned int midr = read_cpuid_id(); > - > - /* Cortex-A15 r0p0..r3p2 affected */ > - if ((midr & 0xff0ffff0) != 0x410fc0f0 || midr > 0x413fc0f2) > - return 0; > - return 1; > + static int errata_fix_needed = -1; > + > + if (unlikely(errata_fix_needed == -1)) { > + unsigned int midr = read_cpuid_id(); > + unsigned int revidr = read_cpuid(CPUID_REVIDR); > + > + /* Cortex-A15 r0p0..r3p2 w/o ECO fix affected */ > + if ((midr & 0xff0ffff0) != 0x410fc0f0 || midr > 0x413fc0f2 || > + (revidr & 0x210) == 0x210) { > + errata_fix_needed = 0; /* No work-around needed */ > + return 0; > + } > + if (revidr & 0x10) > + errata_fix_needed = 1; /* Only TLB flush needed */ > + else > + errata_fix_needed = 2; /* IPI broadcast needed */ > + } > + > + if (errata_fix_needed) > + dummy_flush_tlb_a15_erratum(); > + > + /* Return 1 if IPI broadcast to other cores is needed */ > + return (errata_fix_needed == 2) ? 1: 0; Perhaps this would be cleaner if we had a separate function to initialise an appropriate function pointer for the workaround instead? It might also be faster for non-affected cores (depending on what the above ends up compiling to -- I don't know what ARM GCC does with __builtin_expect). Will
diff --git a/arch/arm/include/asm/cputype.h b/arch/arm/include/asm/cputype.h index 8c25dc4..e5952b7 100644 --- a/arch/arm/include/asm/cputype.h +++ b/arch/arm/include/asm/cputype.h @@ -10,6 +10,7 @@ #define CPUID_TLBTYPE 3 #define CPUID_MPUIR 4 #define CPUID_MPIDR 5 +#define CPUID_REVIDR 6 #ifdef CONFIG_CPU_V7M #define CPUID_EXT_PFR0 0x40 diff --git a/arch/arm/kernel/smp_tlb.c b/arch/arm/kernel/smp_tlb.c index a98b62d..da20db1 100644 --- a/arch/arm/kernel/smp_tlb.c +++ b/arch/arm/kernel/smp_tlb.c @@ -73,12 +73,29 @@ static inline void ipi_flush_bp_all(void *ignored) #ifdef CONFIG_ARM_ERRATA_798181 static int erratum_a15_798181(void) { - unsigned int midr = read_cpuid_id(); - - /* Cortex-A15 r0p0..r3p2 affected */ - if ((midr & 0xff0ffff0) != 0x410fc0f0 || midr > 0x413fc0f2) - return 0; - return 1; + static int errata_fix_needed = -1; + + if (unlikely(errata_fix_needed == -1)) { + unsigned int midr = read_cpuid_id(); + unsigned int revidr = read_cpuid(CPUID_REVIDR); + + /* Cortex-A15 r0p0..r3p2 w/o ECO fix affected */ + if ((midr & 0xff0ffff0) != 0x410fc0f0 || midr > 0x413fc0f2 || + (revidr & 0x210) == 0x210) { + errata_fix_needed = 0; /* No work-around needed */ + return 0; + } + if (revidr & 0x10) + errata_fix_needed = 1; /* Only TLB flush needed */ + else + errata_fix_needed = 2; /* IPI broadcast needed */ + } + + if (errata_fix_needed) + dummy_flush_tlb_a15_erratum(); + + /* Return 1 if IPI broadcast to other cores is needed */ + return (errata_fix_needed == 2) ? 1: 0; } #else static int erratum_a15_798181(void) @@ -97,7 +114,6 @@ static void broadcast_tlb_a15_erratum(void) if (!erratum_a15_798181()) return; - dummy_flush_tlb_a15_erratum(); smp_call_function(ipi_flush_tlb_a15_erratum, NULL, 1); } @@ -109,7 +125,6 @@ static void broadcast_tlb_mm_a15_erratum(struct mm_struct *mm) if (!erratum_a15_798181()) return; - dummy_flush_tlb_a15_erratum(); this_cpu = get_cpu(); a15_erratum_get_cpumask(this_cpu, mm, &mask); smp_call_function_many(&mask, ipi_flush_tlb_a15_erratum, NULL, 1);