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

[Philippe Mathieu-Daudé]

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;