[OpenBIOS] Re: Openbios code for IRQ or interrupt handling?

[Jd Lyons]

I can’t figure out this race condition but it causes an IRQ storm. I feel like I’m in the old days of PC’s when to had IRQ conflicts and had to sort them yourself deep in the bios. As a Mac person I only had to deal with that on a few friends PC’s. Starting the second CPU in a on state rather than halted just makes the race condition worse, twice as fast, and Openbios doesn’t want to get to the prompt, but throwing 3, 8, or 9 CPUs at it in a running state gets me to the prompt, but it ignores -prom-env setting with anything more that three.

300% cpu usage just speeds up the race condition and IRQ storm so IDE craps out before you can load BootX or a linux kernel.

Then noting happens but the IRG storm and GPIO 1 asserting 0, likely to all the other CPUs, and that is likely the race conditions and pulling that low trigger the IRQ storm.

I can’t make it stop, I even tied all IRQ and Interrupts handling to CPU0, and that working until the OS Kenral loads and starts sending stuff to CPU1, which is still in a halted state unless I start it with my hack. Even with only CPU0 dealing with IRQs and Interrupts the race condition is still there and the IRQ storm.

I have to figure out why GPIO 1keeps getting triggered in a loop to pull low????
> On Feb 19, 2025, at 1:29 AM, Jd Lyons  wrote:
>
> Thanks Mark, I got side traced thinking open-pic when I should have been looking at GPIO because it is the one that is the gpio-parent there should be no interrupt-parent property. I think the gpio phandle is 7.
>
> Can you tell me how IRQ’s get assigned to CPU0?
>
> Interrupts?
> > On Feb 18, 2025, at 5:00 PM, Mark Cave-Ayland  wrote:
> >
> > On 18/02/2025 21:34, Jd Lyons via OpenBIOS wrote:
> > > I don’t know why, I can’t seem to get Openbios to set and interrupt-parent in the init.c for any /cpus, this code should work, no?
> > > void add_cpu_nodes(void) {
> > >     int num_cpus = fw_cfg_read_i32(FW_CFG_NB_CPUS);
> > >     printk("Detected %d CPUs\n", num_cpus);
> > >     /* Ensure /cpus node exists */
> > >     phandle cpus_node = dt_find_by_path("/cpus");
> > >     if (!cpus_node) {
> > >         printk("ERROR: /cpus node not found! Delaying CPU setup.\n");
> > >         return;
> > >     }
> > >     /* Wait until the interrupt controller exists */
> > >     phandle intc_node = NULL;
> > >     int retries = 5;
> > >     while (retries-- > 0) {
> > >         intc_node = dt_find_by_path("/pci/mac-io/@40000");
> >
> > Is this for the mac99 machine? If so you probably want /pci@f2000000/mac-io@c/interrupt-controller@40000 (see the output of show-devs for the full device paths).
> > >     if (intc_node) {
> > >         break;
> > >     }
> > >     printk("Waiting for /pci/mac-io/@40000...\\n");
> > >     msleep(100);  // Wait 100ms before retrying
> > > }
> > > if (!intc_node) {
> > >     printk("ERROR: Interrupt controller (/pci/mac-io/@40000) not found! SMP will not work.\\n");
> > >     return;
> > > }
> > > for (int i = 0; i < num_cpus; i++) {
> > >     phandle cpu_node = dt_new_node(cpus_node);
> > >     if (!cpu_node) {
> > >         printk("ERROR: Failed to create CPU node for CPU %d!\\n", i);
> > >         continue;
> > >     }
> > >     dt_set_property_string(cpu_node, "device_type", "cpu");
> > >     dt_set_property_string(cpu_node, "compatible", "PowerPC,G4");
> > >     /* Assign a unique CPU interrupt */
> > >     int cpu_irq[2] = { 16 + i, 0 };
> > >     dt_set_property_cells(cpu_node, "interrupts", cpu_irq, 2);
> > >     printk("CPU %d assigned IRQ %d\\n", i, cpu_irq[0]);
> > >     /* Ensure interrupt-parent is set */
> > >     dt_set_property_phandle(cpu_node, "interrupt-parent", intc_node);
> > >     printk("CPU %d linked to interrupt-parent /pci/mac-io/@40000\\n", i);
> > >     /* Register CPU ID */
> > >     PUSH(i);
> > >     fword("encode-int");
> > >     push_str("reg");
> > >     fword("property");
> > >     fword("finish-device");
> > >     printk("Initialized CPU %d\\n", i);
> > > }
> > >
> > > }
> >
> > ATB,
> >
> > Mark.