Subject: Re: sym scsi driver problem with 2.6.26 or newer debian kernel on p610 (fwd)

From: Michael Ellerman <[email-masked]>
Date: Wed, 24 Jun 2009 16:19:52 +1000

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