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

- From: Christian Zigotzky \<hidden\>
- Date: 2026-11-10 05:40:05 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2026/11/17903229
- Thread: https://ratatoskr.run/linuxppc-dev/2026/10/17797378/t.md

```text


> On 02 November 2026 at 04:39 am, Ritesh Harjani [ref] wrote:
> 
> chzigotzky@xenosoft.de writes:
> 
>> From: Christian Zigotzky A-EON Open Source <redacted>
>> 
>> 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: <redacted>
> 
> 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>
> 
> 
>> 
>> Suggested-by: Darren Stevens <redacted>
>> Tested-by: Christian Zigotzky <redacted>
>> Signed-off-by: Christian Zigotzky A-EON Open Source <redacted>
>> ---
>> 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

Hi Michael,

I would like to ask about the status of my patch.
The patch received a positive review from Ritesh Harjani.
This fix is important for our Nemo boards, otherwise fails to boot with recent kernels.

Thanks,
Christian

```