Re: [PATCH 3/9] intc/grlib_irqmp: implements the multiprocessor status register

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 5/1/24 14:23, Clément Chigot wrote:
> On Fri, Jan 5, 2024 at 12:32 PM Philippe Mathieu-Daudé
> <philmd@linaro.org> wrote:
>>
>> Hi Clément,
>>
>> On 5/1/24 11:24, Clément Chigot wrote:
>>> This implements the multiprocessor status register in grlib-irqmp and bind
>>> it to a start signal, which will be later wired in leon3-generic to
>>> start a cpu.
>>>
>>> Co-developed-by: Frederic Konrad <konrad.frederic@yahoo.fr>
>>> Signed-off-by: Clément Chigot <chigot@adacore.com>
>>> ---
>>>    hw/intc/grlib_irqmp.c | 22 +++++++++++++++++++---
>>>    1 file changed, 19 insertions(+), 3 deletions(-)
>>
>>
>>> @@ -323,6 +334,8 @@ static void grlib_irqmp_reset(DeviceState *d)
>>>
>>>        memset(irqmp->state, 0, sizeof *irqmp->state);
>>>        irqmp->state->parent = irqmp;
>>> +    irqmp->state->mpstatus = ((irqmp->ncpus - 1) << 28)
>>
>> Can you #define this magic '28' number?
>>
>>> +        | ((1 << irqmp->ncpus) - 2);
>>>    }
>>>
>>>    static void grlib_irqmp_realize(DeviceState *dev, Error **errp)
>>> @@ -336,6 +349,9 @@ static void grlib_irqmp_realize(DeviceState *dev, Error **errp)
>>>        }
>>>
>>>        qdev_init_gpio_in(dev, grlib_irqmp_set_irq, MAX_PILS);
>>> +    /* Transitionning from 0 to 1 starts the CPUs.  */
>>
>> What about 1 -> 0?
> 
> It does nothing. I have updated the comment to mention it.
> For the doc (also mention it in the commit message now).
>    | [15:1] Power-down status of CPU [n]: reads ‘1’ = power-down, ‘0’ = running.
>    | Write to start processor n: ‘1’=to start ‘0'=has no effect.

Then grlib_irqmp_write() could be simplified as:

      case MP_STATUS_OFFSET:
-        /* Read Only (no SMP support) */
+        state->mpstatus = deposit32(state->mpstatus,
+                                    value, 0, IRQMP_MAX_CPU);
+        for (unsigned i = 0; i < irqmp->ncpus; i++) {
+            qemu_set_irq(irqmp->start_signal[i],
+                         extract32(value, i, 1));
+        }
          return;