[PATCH] Urgent: powerpc 2.6.20-rc4 dma broken on non-LPAR pseries

[Benjamin Herrenschmidt]

On Wed, 2007-01-10 at 19:16 -0600, Linas Vepstas wrote:
> Paul, please review, apply and send upstream. 
> 
> I marked the subject line as urgent, as I think 2.6.20-rc4 is
> broken for all pSeries non-LPAR systems.
> 
> It appears that the iommu table address is never stored, and thus
> never found, on non-lpar systems. Thus, for example, during boot:
> 
> <7>[   93.067916] PCI: Scanning bus 0001:41
> <7>[   93.068542] PCI: Found 0001:41:01.0 [8086/100f] 000200 00
> <7>[   93.068550] PCI: Calling quirk c0000000007822e0 for 0001:41:01.0
> <7>[   93.069815] PCI: Fixups for bus 0001:41
> <4>[   93.070167] iommu: Device 0001:41:01.0 has no iommu table
> <7>[   93.070251] PCI: Bus scan for 0001:41 returning with max=41
> 
> No iommu table? How can that be? Well, circa line 471 of 
> arch/powerpc/platforms/pseries/iommu.c we see the code:
> 
>    while (dn && PCI_DN(dn) && PCI_DN(dn)->iommu_table == NULL)
>       dn = dn->parent;
> 
> and a few lines later is the surprising print statement about
> the missing table.  Seems that this loop ran unto the end, never 
> once finding a non-null PCI_DN(dn)->iommu_table. 
> 
> The problem can be found a few lines earlier: it sems that the
> value of PCI_DN(dn)->iommu_table is never ever set. Thus, the 
> patch sets it.
> 
> The patch was tested on a Power4 system running in full system 
> partition mode, which is where I saw the problem. It works; I've
> not done any wider testing. Had a breif discussion on this on irc.
> 
> Signed-off-by: Linas Vepstas <linas at austin.ibm.com>

Acked-by: Benjamin Herrenschmidt <benh at kernel.crashing.org>

> ----
>  arch/powerpc/platforms/pseries/iommu.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> Index: linux-2.6.20-rc4/arch/powerpc/platforms/pseries/iommu.c
> ===================================================================
> --- linux-2.6.20-rc4.orig/arch/powerpc/platforms/pseries/iommu.c	2007-01-10 18:38:37.000000000 -0600
> +++ linux-2.6.20-rc4/arch/powerpc/platforms/pseries/iommu.c	2007-01-10 18:40:14.000000000 -0600
> @@ -459,7 +459,8 @@ static void pci_dma_dev_setup_pSeries(st
>  		tbl = kmalloc_node(sizeof(struct iommu_table), GFP_KERNEL,
>  				   phb->node);
>  		iommu_table_setparms(phb, dn, tbl);
> -		dev->dev.archdata.dma_data = iommu_init_table(tbl, phb->node);
> +		PCI_DN(dn)->iommu_table = iommu_init_table(tbl, phb->node);
> +		dev->dev.archdata.dma_data = PCI_DN(dn)->iommu_table;
>  		return;
>  	}
>