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

- From: Madhavan Srinivasan \<maddy@linux.ibm.com\>
- Date: 2026-11-10 06:31:13 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2026/11/17903414
- Thread: https://ratatoskr.run/linuxppc-dev/2026/10/17797378/t.md

```text

On 11/10/26 11:09 AM, Christian Zigotzky wrote:
>
>> 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.
Yes, this is parked for the fixes tree.
Maddy


> 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

```