On 10/5/20 7:44 PM, Eduardo Habkost wrote:
> On Mon, Oct 05, 2020 at 06:40:09PM +0200, Igor Mammedov wrote:
>> On Wed, 30 Sep 2020 12:16:53 +0200
>> Philippe Mathieu-Daudé <f4...@amsat.org> wrote:
>>
>>> +arm/ppc/riscv folks
>>>
>>> On 9/30/20 9:43 AM, Igor Mammedov wrote:
>>>> On Mon, 28 Sep 2020 19:15:24 +0200
>>>> Philippe Mathieu-Daudé <f4...@amsat.org> wrote:
>>>>
>>>>> Let CPUState have a clock source (named 'clk') and CPUClass
>
> The language here confuses me: is this a clock source inside the
> CPU, or just a clock input that can be connected to a clock
> source somewhere?
2nd description, "somewhere". I'll reword.
>
> See also comment below[1].
>
>>>>> have a clock_update() callback. The clock can be optionally
>>>>> set Using qdev_connect_clock_in() from the Clock API.
>>>>> If the clock changes, the optional clock_update() will be
>>>>> called.
>
> What does "clock change" means? Is this just about the
> frequency, or something else?
A frequency changes -- which can be because a parent (in the
clock tree) changed its source using a MUX.
>
> (By reading the Clock API documentation, it looks like it only
> represents the clock frequency, but I'm not sure)
>
>>>>
>>>> the sole user of it is mips cpu, so question is why
>>>> you are making it part of generic CPUm instead of
>>>> MIPSCPUClass/MIPSCPU?
>>>
>>> This is a feature of the CPU, regardless its architecture.
>>>
>>> I expect the other archs to start using it soon.
>>
>> if there aren't any plans to actually to do that,
>> I'd keep it to MIPS class and generalize later when there is demand.
No problem.
>
> I normally don't mind if a feature is generic from the beginning.
> But in this case I'm inclined to agree with Igor. Unless we
> expect to see arch-independent code to use CPUState.clock soon
> (do we?), having CPUState.clock existing but unused by most
> architectures would be misleading.
>
> Also, at least on x86 there are so many different clock sources,
> that I'm not sure it would be a desirable to have a generic clock
> input named "clk".
Well X86 is the arch I'm less confident with. Anyhow if it has
multiple clock sources, I'd expect a Clock MUX block to select
an unique clock to feed the CPU.
>
>>
>>>
>>>>
>>>>>
>>>>> Signed-off-by: Philippe Mathieu-Daudé <f4...@amsat.org>
>>>>> ---
>>>>> include/hw/core/cpu.h | 5 +++++
>>>>> hw/core/cpu.c | 12 ++++++++++++
>>>>> 2 files changed, 17 insertions(+)
>>>>>
>>>>> diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
>>>>> index 6c34798c8b3..6989d90c193 100644
>>>>> --- a/include/hw/core/cpu.h
>>>>> +++ b/include/hw/core/cpu.h
>>>>> @@ -31,6 +31,7 @@
>>>>> #include "qemu/thread.h"
>>>>> #include "qemu/plugin.h"
>>>>> #include "qom/object.h"
>>>>> +#include "hw/clock.h"
>>>>>
>>>>> typedef int (*WriteCoreDumpFunction)(const void *buf, size_t size,
>>>>> void *opaque);
>>>>> @@ -155,6 +156,7 @@ struct TranslationBlock;
>>>>> * @disas_set_info: Setup architecture specific components of
>>>>> disassembly info
>>>>> * @adjust_watchpoint_address: Perform a target-specific adjustment to an
>>>>> * address before attempting to match it against watchpoints.
>>>>> + * @clock_update: Callback for input clock changes
>>>>> *
>>>>> * Represents a CPU family or model.
>>>>> */
>>>>> @@ -176,6 +178,7 @@ struct CPUClass {
>>>>> unsigned size, MMUAccessType
>>>>> access_type,
>>>>> int mmu_idx, MemTxAttrs attrs,
>>>>> MemTxResult response, uintptr_t
>>>>> retaddr);
>>>>> + void (*clock_update)(CPUState *cpu);
>>>>> bool (*virtio_is_big_endian)(CPUState *cpu);
>>>>> int (*memory_rw_debug)(CPUState *cpu, vaddr addr,
>>>>> uint8_t *buf, int len, bool is_write);
>>>>> @@ -316,6 +319,7 @@ struct qemu_work_item;
>>>>> * QOM parent.
>>>>> * @nr_cores: Number of cores within this CPU package.
>>>>> * @nr_threads: Number of threads within this CPU.
>>>>> + * @clock: this CPU source clock (an output clock of another device)
>
> [1]
>
> What does "source clock" means? Is this the same as "clock input"?
Yes, for clocks it is common to use source/sink instead of input/output.
I'll try to reword.
>
>
>>>>> * @running: #true if CPU is currently running (lockless).
>>>>> * @has_waiter: #true if a CPU is currently waiting for the cpu_exec_end;
>>>>> * valid under cpu_list_lock.
>>>>> @@ -400,6 +404,7 @@ struct CPUState {
>>>>> int num_ases;
>>>>> AddressSpace *as;
>>>>> MemoryRegion *memory;
>>>>> + Clock *clock;
>>>>>
>>>>> void *env_ptr; /* CPUArchState */
>>>>> IcountDecr *icount_decr_ptr;
>>>>> diff --git a/hw/core/cpu.c b/hw/core/cpu.c
>>>>> index c55c09f734c..37fcff3ec64 100644
>>>>> --- a/hw/core/cpu.c
>>>>> +++ b/hw/core/cpu.c
>>>>> @@ -30,6 +30,7 @@
>>>>> #include "qemu/qemu-print.h"
>>>>> #include "sysemu/tcg.h"
>>>>> #include "hw/boards.h"
>>>>> +#include "hw/qdev-clock.h"
>>>>> #include "hw/qdev-properties.h"
>>>>> #include "trace/trace-root.h"
>>>>> #include "qemu/plugin.h"
>>>>> @@ -247,6 +248,16 @@ void cpu_reset(CPUState *cpu)
>>>>> trace_guest_cpu_reset(cpu);
>>>>> }
>>>>>
>>>>> +static void cpu_clk_update(void *opaque)
>>>>> +{
>>>>> + CPUState *cpu = opaque;
>>>>> + CPUClass *cc = CPU_GET_CLASS(cpu);
>>>>> +
>>>>> + if (cc->clock_update) {
>>>>> + cc->clock_update(cpu);
>>>>> + }
>>>>> +}
>>>>> +
>>>>> static void cpu_common_reset(DeviceState *dev)
>>>>> {
>>>>> CPUState *cpu = CPU(dev);
>>>>> @@ -367,6 +378,7 @@ static void cpu_common_initfn(Object *obj)
>>>>> /* the default value is changed by qemu_init_vcpu() for softmmu */
>>>>> cpu->nr_cores = 1;
>>>>> cpu->nr_threads = 1;
>>>>> + cpu->clock = qdev_init_clock_in(DEVICE(obj), "clk", cpu_clk_update,
>>>>> cpu);
>>>>>
>>>>> qemu_mutex_init(&cpu->work_mutex);
>>>>> QSIMPLEQ_INIT(&cpu->work_list);
>>>>
>>>
>>
>
