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

On 11/02/2026 04:34 AM, Ritesh Harjani (IBM) 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>

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

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

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