Date: Wed, 14 May 2014 19:11:15 +0000 (UTC) From: Mark Murray <markm@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r266083 - in head/sys/arm: arm include Message-ID: <201405141911.s4EJBFZZ097826@svn.freebsd.org>
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Author: markm Date: Wed May 14 19:11:15 2014 New Revision: 266083 URL: http://svnweb.freebsd.org/changeset/base/266083 Log: Give suitably-endowed ARMs a register similar to the x86 TSC register. Here, "suitably endowed" means that the System Control Coprocessor (#15) has Performance Monitoring Registers, including a CCNT (Cycle Count) register. The CCNT register is used in a way similar to the TSC register in x86 processors by the get_cyclecount(9) function. The entropy-harvesting thread is a heavy user of this function, and will benefit from not having to call binuptime(9) instead. One problem with the CCNT register is that it is 32-bit only, so the upper 32-bits of the returned number are always 0. The entropy harvester does not care, but in case any one else does, follow-up work may include an interrup trap to increment an upper-32-bit counter on CCNT overflow. Another problem is that the CCNT register is not readable in user-mode code; in can be made readable by userland, but then it is also writable, and so is a good chunk of the PMU system. For that reason, the CCNT is not enabled for user-mode access in this commit. Like the x86, there is one CCNT per core, so they don't all run in perfect sync. Reviewed by: ian@ (an earlier version) Tested by: ian@ (same earlier version) Committed from: WANDBOARD-QUAD Modified: head/sys/arm/arm/cpufunc.c head/sys/arm/include/cpu.h Modified: head/sys/arm/arm/cpufunc.c ============================================================================== --- head/sys/arm/arm/cpufunc.c Wed May 14 19:02:00 2014 (r266082) +++ head/sys/arm/arm/cpufunc.c Wed May 14 19:11:15 2014 (r266083) @@ -1398,6 +1398,37 @@ arm10_setup(args) } #endif /* CPU_ARM9E || CPU_ARM10 */ +#if defined(CPU_ARM1136) || defined(CPU_ARM1176) \ + || defined(CPU_MV_PJ4B) \ + || defined(CPU_CORTEXA) || defined(CPU_KRAIT) +static __inline void +cpu_scc_setup_ccnt(void) +{ +/* This is how you give userland access to the CCNT and PMCn + * registers. + * BEWARE! This gives write access also, which may not be what + * you want! + */ +#ifdef _PMC_USER_READ_WRITE_ + /* Set PMUSERENR[0] to allow userland access */ + __asm volatile ("mcr p15, 0, %0, c9, c14, 0\n\t" + : + : "r"(0x00000001)); +#endif + /* Set up the PMCCNTR register as a cyclecounter: + * Set PMINTENCLR to 0xFFFFFFFF to block interrupts + * Set PMCR[2,0] to enable counters and reset CCNT + * Set PMCNTENSET to 0x80000000 to enable CCNT */ + __asm volatile ("mcr p15, 0, %0, c9, c14, 2\n\t" + "mcr p15, 0, %1, c9, c12, 0\n\t" + "mcr p15, 0, %2, c9, c12, 1\n\t" + : + : "r"(0xFFFFFFFF), + "r"(0x00000005), + "r"(0x80000000)); +} +#endif + #if defined(CPU_ARM1136) || defined(CPU_ARM1176) struct cpu_option arm11_options[] = { { "cpu.cache", BIC, OR, (CPU_CONTROL_IC_ENABLE | CPU_CONTROL_DC_ENABLE) }, @@ -1501,6 +1532,8 @@ arm11x6_setup(char *args) /* And again. */ cpu_idcache_wbinv_all(); + + cpu_scc_setup_ccnt(); } #endif /* CPU_ARM1136 || CPU_ARM1176 */ @@ -1535,6 +1568,8 @@ pj4bv7_setup(args) /* And again. */ cpu_idcache_wbinv_all(); + + cpu_scc_setup_ccnt(); } #endif /* CPU_MV_PJ4B */ @@ -1582,6 +1617,8 @@ cortexa_setup(char *args) #ifdef SMP armv7_auxctrl((1 << 6) | (1 << 0), (1 << 6) | (1 << 0)); /* Enable SMP + TLB broadcasting */ #endif + + cpu_scc_setup_ccnt(); } #endif /* CPU_CORTEXA */ Modified: head/sys/arm/include/cpu.h ============================================================================== --- head/sys/arm/include/cpu.h Wed May 14 19:02:00 2014 (r266082) +++ head/sys/arm/include/cpu.h Wed May 14 19:11:15 2014 (r266083) @@ -14,11 +14,26 @@ void swi_vm(void *); static __inline uint64_t get_cyclecount(void) { +/* This '#if' asks the question 'Does CP15/SCC include performance counters?' */ +#if defined(CPU_ARM1136) || defined(CPU_ARM1176) \ + || defined(CPU_MV_PJ4B) \ + || defined(CPU_CORTEXA) || defined(CPU_KRAIT) + uint32_t ccnt; + uint64_t ccnt64; + + /* + * Read PMCCNTR. Curses! Its only 32 bits. + * TODO: Fix this by catching overflow with interrupt? + */ + __asm __volatile("mrc p15, 0, %0, c9, c13, 0": "=r" (ccnt)); + ccnt64 = (uint64_t)ccnt; + return (ccnt64); +#else /* No performance counters, so use binuptime(9). This is slooooow */ struct bintime bt; binuptime(&bt); return ((uint64_t)bt.sec << 56 | bt.frac >> 8); - +#endif } #endif
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