that some #ifdef SMP code is also conditional on __ARM_ARCH >= 7; we don't
support SMP on armv6, but some drivers and modules are compiled with it
forced on via the compiler command line.
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
really need it. That would be almost everywhere it was included. Add
it in a couple files that really do need it and were previously getting
it by accident via another header.
structure with the first 4 registers to allow a wider range of boot
loaders to work. Future commits will make use of this to centralize
support for the different loaders.
passing a pointer to an opaque clockframe structure and requiring the
MD code to supply CLKF_FOO() macros to extract needed values out of the
opaque structure, just pass the needed values directly. In practice this
means passing the pair (usermode, pc) to hardclock() and profclock() and
passing the boolean (usermode) to hardclock_cpu() and hardclock_process().
Other details:
- Axe clockframe and CLKF_FOO() macros on all architectures. Basically,
all the archs were taking a trapframe and converting it into a clockframe
one way or another. Now they can just extract the PC and usermode values
directly out of the trapframe and pass it to fooclock().
- Renamed hardclock_process() to hardclock_cpu() as the latter is more
accurate.
- On Alpha, we now run profclock() at hz (profhz == hz) rather than at
the slower stathz.
- On Alpha, for the TurboLaser machines that don't have an 8254
timecounter, call hardclock() directly. This removes an extra
conditional check from every clock interrupt on Alpha on the BSP.
There is probably room for even further pruning here by changing Alpha
to use the simplified timecounter we use on x86 with the lapic timer
since we don't get interrupts from the 8254 on Alpha anyway.
- On x86, clkintr() shouldn't ever be called now unless using_lapic_timer
is false, so add a KASSERT() to that affect and remove a condition
to slightly optimize the non-lapic case.
- Change prototypeof arm_handler_execute() so that it's first arg is a
trapframe pointer rather than a void pointer for clarity.
- Use KCOUNT macro in profclock() to lookup the kernel profiling bucket.
Tested on: alpha, amd64, arm, i386, ia64, sparc64
Reviewed by: bde (mostly)
being defined, define and use a new MD macro, cpu_spinwait(). It only
expands to something on i386 and amd64, so the compiled code should be
identical.
Name of the macro found by: jhb
Reviewed by: jhb
It only supports sa1110 (on simics) right now, but xscale support should come
soon.
Some of the initial work has been provided by :
Stephane Potvin <sepotvin at videotron.ca>
Most of this comes from NetBSD.
