Re: [PATCH] Connecting the SB600's i8259 controller rather in pasemi's pci.c than in pasemi's setup.c.

[Christian Zigotzky]

On 27/07/26 15:43, Christophe Leroy (CS GROUP) wrote:
>
> Should be better in arch/powerpc/platforms/pasemi/pasemi.h
>

Hello Christophe,

Thank you for your answer. I modified the patch today. The Nemo board 
boots without any problems if I compile the RC5 of kernel 7.2 with this 
patch.

Could you please check the following modified patch?

Thanks,
Christian

---

powerpc/pasemi: Move Nemo i8259 initialization to pci.c

The Nemo board requires the PCIe ports to be initialized before the
SB600 ISA bridge can be accessed.

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.

Suggested-by: Darren Stevens <darren@xxxxxxxxxxxxxxxx>
Tested-by: Christian Zigotzky <chzigotzky@xxxxxxxxxxx>
Signed-off-by: Christian Zigotzky <chzigotzky@xxxxxxxxxxx>

---
v2:
- Move Nemo i8259 initialization out of pas_init_IRQ() and into
  pas_add_bridge() after the ISA bridge has been discovered.
- Change nemo_init_IRQ() to no longer depend on the MPIC instance passed
  from the IRQ setup path.
- Move the nemo_init_IRQ() declaration to pasemi.h and add a no-op stub
  for non-Nemo builds.
- Fix missing prototype warning reported by Christophe Leroy.
- Fix indentation and clean up the commit message.

diff -rupN a/arch/powerpc/platforms/pasemi/pasemi.h 
b/arch/powerpc/platforms/pasemi/pasemi.h
--- a/arch/powerpc/platforms/pasemi/pasemi.h    2026-07-26 
23:45:48.000000000 +0200
+++ b/arch/powerpc/platforms/pasemi/pasemi.h    2026-07-28 
07:44:31.924168227 +0200
@@ -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
+extern 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 -rupN a/arch/powerpc/platforms/pasemi/pci.c 
b/arch/powerpc/platforms/pasemi/pci.c
--- a/arch/powerpc/platforms/pasemi/pci.c    2026-07-26 
23:45:48.000000000 +0200
+++ b/arch/powerpc/platforms/pasemi/pci.c    2026-07-28 
07:34:37.036634023 +0200
@@ -265,6 +265,11 @@ static int __init pas_add_bridge(struct
      */
     isa_bridge_find_early(hose);

+    /*
+     * ISA bridge is now active, add the i8259 cascade (if needed)
+     */
+    nemo_init_IRQ();
+
     return 0;
 }

diff -rupN a/arch/powerpc/platforms/pasemi/setup.c 
b/arch/powerpc/platforms/pasemi/setup.c
--- a/arch/powerpc/platforms/pasemi/setup.c    2026-07-26 
23:45:48.000000000 +0200
+++ b/arch/powerpc/platforms/pasemi/setup.c    2026-07-28 
07:54:54.147863161 +0200
@@ -214,10 +214,12 @@ static void sb600_8259_cascade(struct ir
     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);
@@ -228,14 +230,10 @@ static void __init nemo_init_IRQ(struct
     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)
@@ -297,9 +295,7 @@ static __init void pas_init_IRQ(void)
         irq_set_irq_type(nmi_virq, IRQ_TYPE_EDGE_RISING);
         mpic_unmask_irq(irq_get_irq_data(nmi_virq));
     }
-
-    nemo_init_IRQ(mpic);
-
+
     of_node_put(mpic_node);
     of_node_put(root);
 }