Re: [PATCH] Connecting the SB600's i8259 controller rather in pasemi's pci.c than in pasemi's setup.c.

["Christophe Leroy (CS GROUP)" <chleroy@kernel.org>]

Le 01/07/2026 à 14:59, Christian Zigotzky a écrit :
> Hello,
> 
> Here is the email without HTML (Sorry):
> 
> The Nemo board [1] doesn’t boot without this patch. Darren explained it really well:
> 
> Originally we initialised the PCI-e ports in setup arch, this is quite early, and it seems uses some kernel functions that were not recommended (They changed a whole lot of different platforms at the same time for the same reason)
> 
> After this we added the ISA bridge, then the kernel would init the IRQ contollers.
> 
> The patch that broke booting on the X1000 moved the pas_pci_init to a node in the machine description, where it called later in the boot sequence. Unfortunately this is after we've tried to add the i8259 contoller from the pas_init_IRQ. Since our ISA bridge can't be found until we've connected the PCI-e ports the system tries to write to registers that aren't yet mapped - result a kernel panic, but before console I/O has been initialised so it appears to be a hang. We had a similar problem when they were introducing Radix support.
> 
> My patch changes our code so that it works with the new kernel code in place. Basically I moved the code that adds the i8259 cascade to after we've scanned for the ISA bridge where I know it will work.
> 
> Hopefully this makes sense, shout out if it doesn't.
> 
> Regards
> Darren
> 
> [1] https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FAmigaOne_X1000&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7Cb415e9e7a26c4d8e3c6b08ded770c1b7%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639185077045605675%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C60000%7C%7C%7C&sdata=EgGtT9Kj7aqkWWcIIxfPpYRulro8rUA%2F%2Bsp9bhy%2Bjqo%3D&reserved=0
> 
> Signed-off-by: Christian Zigotzky <chzigotzky@xenosoft.de>


The commit message will look strange when picking-up this email, you 
should resend with a cleaned commit message.

> ---
>   arch/powerpc/platforms/pasemi/pci.c   | 7 +++++++
>   arch/powerpc/platforms/pasemi/setup.c | 7 ++++---
>   2 files changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/pasemi/pci.c b/arch/powerpc/platforms/pasemi/pci.c
> index 2df955274652..7208c325bfc5 100644
> --- a/arch/powerpc/platforms/pasemi/pci.c
> +++ b/arch/powerpc/platforms/pasemi/pci.c
> @@ -25,6 +25,8 @@
>   
>   #define PA_PXP_CFA(bus, devfn, off) (((bus) << 20) | ((devfn) << 12) | (off))
>   
> +extern void nemo_init_IRQ(void);
> +

Should be better in arch/powerpc/platforms/pasemi/pasemi.h

>   static inline int pa_pxp_offset_valid(u8 bus, u8 devfn, int offset)
>   {
>   	/* Device 0 Function 0 is special: It's config space spans function 1 as
> @@ -265,6 +267,11 @@ static int __init pas_add_bridge(struct device_node *dev)
>   	 */
>   	isa_bridge_find_early(hose);
>   
> +	/*
> +	 * ISA brigde is now active, add the i8259 cascade (if needed)
> +	 */
> +	nemo_init_IRQ();
> +
>   	return 0;
>   }
>   
> diff --git a/arch/powerpc/platforms/pasemi/setup.c b/arch/powerpc/platforms/pasemi/setup.c
> index d03b41336901..eec74611be46 100644
> --- a/arch/powerpc/platforms/pasemi/setup.c
> +++ b/arch/powerpc/platforms/pasemi/setup.c
> @@ -214,10 +214,12 @@ static void sb600_8259_cascade(struct irq_desc *desc)
>   	chip->irq_eoi(&desc->irq_data);
>   }
>   
> -static void __init nemo_init_IRQ(struct mpic *mpic)
> +void nemo_init_IRQ(void)
>   {
>   	struct device_node *np;
>   	int gpio_virq;
> +        struct mpic *mpic;
> +
>   	/* Connect the SB600's legacy i8259 controller */
>   	np = of_find_node_by_path("/pxp@0,e0000000");
>   	i8259_init(np, 0);
> @@ -228,6 +230,7 @@ static void __init nemo_init_IRQ(struct mpic *mpic)
>   	irq_set_chained_handler(gpio_virq, sb600_8259_cascade);
>   	mpic_unmask_irq(irq_get_irq_data(gpio_virq));
>   
> +	mpic = irq_get_chip_data(gpio_virq);
>   	irq_set_default_domain(mpic->irqhost);
>   }
>   
> @@ -298,8 +301,6 @@ static __init void pas_init_IRQ(void)
>   		mpic_unmask_irq(irq_get_irq_data(nmi_virq));
>   	}
>   
> -	nemo_init_IRQ(mpic);
> -
>   	of_node_put(mpic_node);
>   	of_node_put(root);
>   }

Build fails:

   CC      arch/powerpc/platforms/pasemi/setup.o
arch/powerpc/platforms/pasemi/setup.c:217:6: error: no previous 
prototype for 'nemo_init_IRQ' [-Werror=missing-prototypes]
   217 | void nemo_init_IRQ(void)
       |      ^~~~~~~~~~~~~
cc1: all warnings being treated as errors
make[5]: *** [scripts/Makefile.build:289: 
arch/powerpc/platforms/pasemi/setup.o] Error 1
make[4]: *** [scripts/Makefile.build:549: arch/powerpc/platforms/pasemi] 
Error 2
make[3]: *** [scripts/Makefile.build:549: arch/powerpc/platforms] Error 2
make[2]: *** [scripts/Makefile.build:549: arch/powerpc] Error 2
make[1]: *** [/home/chleroy/linux-powerpc/Makefile:2184: .] Error 2
make: *** [Makefile:248: __sub-make] Error 2