Re: [PATCH] powerpc/pasemi: Defer Nemo IRQ initialization

[Christian Zigotzky <chzigotzky@xenosoft.de>]

On 11/02/2026 04:34 AM, Ritesh Harjani (IBM) wrote:
> chzigotzky@xenosoft.de writes:
>
>> From: Christian Zigotzky A-EON Open Source <info@xenosoft.de>
>>
>> Since pas_pci_init() is now called later during boot, the i8259
>> initialization in pas_init_IRQ() happens too early and accesses
>> registers that are not yet mapped, preventing the board from booting.
>>
>> Move the Nemo-specific i8259 initialization to pas_add_bridge(),
>> after the ISA bridge has been discovered.
>
> That make sense to me. The patch looks good. However, shouldn't we also
> add Fixes tag and Cc: stable tag - so that this gets backported to older
> stable kernels.
>
>
> Fixes: c144bc719234 ("powerpc/pasemi: Move PHB discovery")
> Cc: stable@vger.kernel.org
>
> I think the fixes tag should be above - but feel free to correct that.
>
> Otherwise looks good to me. Feel free to add:
> Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
>
Great! Just for info. I don't need this patch for the stable long-term 
kernel 5.10 but it is at least necessary for the stable long-term 
kernels 6.12 [1] and 6.18.

- Christian

[1] 
https://raw.githubusercontent.com/chzigotzky/kernels/refs/heads/6_12/patches/X1000/pas_pci_init_v6.patch
>> Suggested-by: Darren Stevens <darren@stevens-zone.net>
>> Tested-by: Christian Zigotzky <chzigotzky@xenosoft.de>
>> Signed-off-by: Christian Zigotzky A-EON Open Source <info@xenosoft.de>
>> ---
>>   arch/powerpc/platforms/pasemi/pasemi.h |  6 ++++++
>>   arch/powerpc/platforms/pasemi/pci.c    |  5 +++++
>>   arch/powerpc/platforms/pasemi/setup.c  | 12 ++++--------
>>   3 files changed, 15 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/powerpc/platforms/pasemi/pasemi.h b/arch/powerpc/platforms/pasemi/pasemi.h
>> index 6f6743b8e48d..01bcfa258625 100644
>> --- a/arch/powerpc/platforms/pasemi/pasemi.h
>> +++ b/arch/powerpc/platforms/pasemi/pasemi.h
>> @@ -7,6 +7,12 @@ extern void pas_pci_init(void);
>>   struct pci_dev;
>>   extern void pas_pci_dma_dev_setup(struct pci_dev *dev);
>>   
>> +#ifdef CONFIG_PPC_PASEMI_NEMO
>> +void __init nemo_init_IRQ(void);
>> +#else
>> +static inline void __init nemo_init_IRQ(void) { }
>> +#endif
>> +
>>   void __iomem *__init pasemi_pci_getcfgaddr(struct pci_dev *dev, int offset);
>>   
>>   extern void __init pasemi_map_registers(void);
>> diff --git a/arch/powerpc/platforms/pasemi/pci.c b/arch/powerpc/platforms/pasemi/pci.c
>> index 2df955274652..fb53782da7ec 100644
>> --- a/arch/powerpc/platforms/pasemi/pci.c
>> +++ b/arch/powerpc/platforms/pasemi/pci.c
>> @@ -265,6 +265,11 @@ static int __init pas_add_bridge(struct device_node *dev)
>>   	 */
>>   	isa_bridge_find_early(hose);
>>   
>> +	/*
>> +	 * ISA bridge 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 45792ecd5dfd..7a961f2a228f 100644
>> --- a/arch/powerpc/platforms/pasemi/setup.c
>> +++ b/arch/powerpc/platforms/pasemi/setup.c
>> @@ -216,10 +216,12 @@ 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 __init 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);
>> @@ -230,14 +232,10 @@ 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);
>>   }
>>   
>> -#else
>> -
>> -static inline void nemo_init_IRQ(struct mpic *mpic)
>> -{
>> -}
>>   #endif
>>   
>>   static __init void pas_init_IRQ(void)
>> @@ -300,8 +298,6 @@ 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);
>>   }
>> -- 
>> 2.43.0


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