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target/mips/cpu: Make cp0_count_rate a property 

Since not all CPU implementations use a cores use a CP0 timer
at half the frequency of the CPU, make this variable a property.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20201012095804.3335117-11-f4bug@amsat.org>
This commit is contained in:
Philippe Mathieu-Daudé 2020-10-12 11:57:53 +02:00
parent 68b981aa76
commit d0bec217ee
2 changed files with 20 additions and 8 deletions
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19
target/mips/cpu.c
View File

@ -26,7 +26,7 @@
#include "qemu/module.h"
#include "sysemu/kvm.h"
#include "exec/exec-all.h"
#include "hw/qdev-properties.h"
static void mips_cpu_set_pc(CPUState *cs, vaddr value)
{
@ -135,12 +135,7 @@ static void mips_cpu_disas_set_info(CPUState *s, disassemble_info *info)
}
/*
* Since commit 6af0bf9c7c3 this model assumes a CPU clocked at 200MHz
* and a CP0 timer running at half the clock of the CPU (cp0_count_rate = 2).
*
* TIMER_FREQ_HZ = CPU_FREQ_HZ / CP0_COUNT_RATE = 200 MHz / 2 = 100 MHz
*
* TIMER_PERIOD_NS = 1 / TIMER_FREQ_HZ = 10 ns
* Since commit 6af0bf9c7c3 this model assumes a CPU clocked at 200MHz.
*/
#define CPU_FREQ_HZ_DEFAULT 200000000
#define CP0_COUNT_RATE_DEFAULT 2
@ -149,7 +144,7 @@ static void mips_cp0_period_set(MIPSCPU *cpu)
{
CPUMIPSState *env = &cpu->env;
env->cp0_count_ns = muldiv64(NANOSECONDS_PER_SECOND, CP0_COUNT_RATE_DEFAULT,
env->cp0_count_ns = muldiv64(NANOSECONDS_PER_SECOND, cpu->cp0_count_rate,
CPU_FREQ_HZ_DEFAULT);
}
@ -202,6 +197,13 @@ static ObjectClass *mips_cpu_class_by_name(const char *cpu_model)
return oc;
}
static Property mips_cpu_properties[] = {
/* CP0 timer running at half the clock of the CPU */
DEFINE_PROP_UINT32("cp0-count-rate", MIPSCPU, cp0_count_rate,
CP0_COUNT_RATE_DEFAULT),
DEFINE_PROP_END_OF_LIST()
};
static void mips_cpu_class_init(ObjectClass *c, void *data)
{
MIPSCPUClass *mcc = MIPS_CPU_CLASS(c);
@ -211,6 +213,7 @@ static void mips_cpu_class_init(ObjectClass *c, void *data)
device_class_set_parent_realize(dc, mips_cpu_realizefn,
&mcc->parent_realize);
device_class_set_parent_reset(dc, mips_cpu_reset, &mcc->parent_reset);
device_class_set_props(dc, mips_cpu_properties);
cc->class_by_name = mips_cpu_class_by_name;
cc->has_work = mips_cpu_has_work;

9
target/mips/cpu.h
View File

@ -1151,6 +1151,7 @@ struct CPUMIPSState {
/**
* MIPSCPU:
* @env: #CPUMIPSState
* @cp0_count_rate: rate at which the coprocessor 0 counter increments
*
* A MIPS CPU.
*/
@ -1161,6 +1162,14 @@ struct MIPSCPU {
CPUNegativeOffsetState neg;
CPUMIPSState env;
/*
* The Count register acts as a timer, incrementing at a constant rate,
* whether or not an instruction is executed, retired, or any forward
* progress is made through the pipeline. The rate at which the counter
* increments is implementation dependent, and is a function of the
* pipeline clock of the processor, not the issue width of the processor.
*/
unsigned cp0_count_rate;
};