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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