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

On 02 November 2026 at 04:39 am, Ritesh Harjani [off-list ref] wrote:

chzigotzky@xenosoft.de writes:

quoted

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>

quoted

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