On Wed, 2009-06-24 at 15:56 +1000, Benjamin Herrenschmidt wrote:
  
  
    On Wed, 2009-06-24 at 15:53 +1000, Michael Ellerman wrote:
    
    
      Doesn't fix my machine :/
      
    
    That doesn't make sense ... What if you remove the bit inside the ifdef
CONFIG_MPIC_BROKEN_REGREAD in _mpic_read() ?
If that makes a difference, then it would be interesting to add a printk
in there that prints what the original value "val" is and what we have
in the shadow...
    
  
  
With this patch it boots:
diff --git a/arch/powerpc/sysdev/mpic.c b/arch/powerpc/sysdev/mpic.c
index 2353adc..fc17289 100644
--- a/arch/powerpc/sysdev/mpic.c
+++ b/arch/powerpc/sysdev/mpic.c
@@ -231,13 +231,16 @@ static inline u32 _mpic_irq_read(struct mpic *mpic, unsign
        unsigned int    isu = src_no >> mpic->isu_shift;
        unsigned int    idx = src_no & mpic->isu_mask;
        unsigned int    val;
+       unsigned int    shadow;
 
        val = _mpic_read(mpic->reg_type, &mpic->isus[isu],
                         reg + (idx * MPIC_INFO(IRQ_STRIDE)));  
 #ifdef CONFIG_MPIC_BROKEN_REGREAD
-       if (reg == 0)
-               val = (val & (MPIC_VECPRI_MASK | MPIC_VECPRI_ACTIVITY)) |
+       if (reg == 0) {
+               shadow = (val & (MPIC_VECPRI_MASK | MPIC_VECPRI_ACTIVITY)) |
                        mpic->isu_reg0_shadow[idx];
+               printk("%s: val 0x%x shadow 0x%x\n", __func__, val, shadow);
+       }
 #endif
        return val;
 }
And I see:
sym53c8xx 0000:00:0c.0: enabling device (0140 -> 0143)
sym0: <896> rev 0x7 at pci 0000:00:0c.0 irq 17
sym0: No NVRAM, ID 7, Fast-40, SE, parity checking
_mpic_irq_read: val 0x80480004 shadow 0x80080014
_mpic_irq_read: val 0x480004 shadow 0x480004
cheers