[Skiboot] [PATCH 6/9] phb4: Fix MMIO enable with fence recovery

[Michael Neuling]

On Fri, 2017-10-20 at 14:56 +0200, Benjamin Herrenschmidt wrote:
> On Fri, 2017-10-20 at 22:59 +1100, Michael Neuling wrote:
> > PHB fatal error recovery needs MMIO enabled otherwise the PHB will
> > freeze the PE once the driver starts accessing the device again.
> 
> I don't understand the patch and how it relates to the above changelog.
> 
> You seem to be forcing any write to the PCI command register to set
> those 2 bits. It feels to me like the real problem might be in the
> callers ... How come are those 2 bits cleared and not restored
> properly by Linux ?

I agree, I do feel like I'm papering over another problem.

I don't remember why we had to do this original patch on DD1. The commit message
doesn't explain it either and I don't know why kexec would change between DD1
and DD2.

/me shakes fist at past mikey.

commit 2d4f3cf4bcfa7cfd6e4dddb0ca5a4cbaedc27a15
Author: Michael Neuling <mikey at neuling.org>
Date:   Wed Nov 16 16:49:24 2016 +1100

    phb4: Fix config space enable bits on DD1
    
    Fix enabling config space on DD1.
    
    Without this PCI devices disappear on kexec.
    
    Signed-off-by: Michael Neuling <mikey at neuling.org>
    Signed-off-by: Stewart Smith <stewart at linux.vnet.ibm.com>


Mikey

> 
> > Signed-off-by: Michael Neuling <mikey at neuling.org>
> > ---
> >  hw/phb4.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/hw/phb4.c b/hw/phb4.c
> > index 0170e43a89..0841136cc7 100644
> > --- a/hw/phb4.c
> > +++ b/hw/phb4.c
> > @@ -421,7 +421,7 @@ static int64_t phb4_rc_write(struct phb4 *p, uint32_t
> > offset, uint8_t sz,
> >  		break;
> >  	default:
> >  		/* Workaround PHB config space enable */
> > -		if ((p->rev == PHB4_REV_NIMBUS_DD10) && (reg ==
> > PCI_CFG_CMD))
> > +		if (reg == PCI_CFG_CMD)
> >  			val |= PCI_CFG_CMD_MEM_EN |
> > PCI_CFG_CMD_BUS_MASTER_EN;
> >  		PHBLOGCFG(p, "000 CFG%02d Wr %02x=%08x\n", 8 * sz, reg,
> > val);
> >  		if (use_asb)
> 
>