Re: [PATCH 1/4] powerpc/pseries/iommu: Update call to ibm,query-pe-dma-windows

[Leonardo Bras]

On Tue, 2020-06-23 at 11:12 +1000, Alexey Kardashevskiy wrote:
[snip]
> > > > +static int query_ddw_out_sz(struct device_node *par_dn)
> > > 
> > > Can easily be folded into query_ddw().
> > 
> > Sure, but it will get inlined by the compiler, and I think it reads
> > better this way. 
> > I mean, I understand you have a reason to think it's better to fold it
> > in query_ddw(), and I would like to better understand that to improve
> > my code in the future.
> 
> You have numbers 5 and 6 (the number of parameters) twice in the file,
> this is why I brought it up. query_ddw_out_sz() can potentially return
> something else than 5 or 6 and you will have to change the callsite(s)
> then, since these are not macros, this allows to think there may be more
> places with 5 and 6. Dunno. A single function will simplify things imho.

That's a good point. Thanks!

> 
> 
> > > > +{
> > > > +	int ret;
> > > > +	u32 ddw_ext[3];
> > > > +
> > > > +	ret = of_property_read_u32_array(par_dn, "ibm,ddw-extensions",
> > > > +					 &ddw_ext[0], 3);
> > > > +	if (ret || ddw_ext[0] < 2 || ddw_ext[2] != 1)
> > > 
> > > Oh that PAPR thing again :-/
> > > 
> > > ===
> > > The âibm,ddw-extensionsâ property value is a list of integers the first
> > > integer indicates the number of extensions implemented and subsequent
> > > integers, one per extension, provide a value associated with that
> > > extension.
> > > ===
> > > 
> > > So ddw_ext[0] is length.
> > > Listindex==2 is for "reset" says PAPR and
> > > Listindex==3 is for this new 64bit "largest_available_block".
> > > 
> > > So I'd expect ddw_ext[2] to have the "reset" token and ddw_ext[3] to
> > > have "1" for this new feature but indexes are smaller. I am confused.
> > > Either way these "2" and "3" needs to be defined in macros, "0" probably
> > > too.
> > 
> > Remember these indexes are not C-like 0-starting indexes, where the
> > size would be Listindex==1.
> 
> Yeah I can see that is the assumption but out of curiosity - is it
> written anywhere? Across PAPR, they index bytes from 1 but bits from 0 :-/

>From LoPAR: 
The âibm,ddw-extensionsâ property value is a list of integers the first
integer indicates the number of extensions implemented and subsequent
integers, one per extension, provide a value associated with that
extension.

And the list/table then shows extensions from 2 on onwards:
List index 2 : Token of the ibm,reset-pe-dma-windows RTAS Call
(...)

> Either way make them macros.
> 
> 
> > Basically, in C-like array it's :
> > a[0] == size, 
> > a[1] == reset_token, 
> > a[2] == new 64bit "largest_available_block"
> > 
> > > Please post 'lsprop "ibm,ddw-extensions"' here. Thanks,
> > 
> > Sure:
> > [root@host pci@800000029004005]# lsprop "ibm,ddw-extensions"
> > ibm,dd
> > w-extensions
> >                  00000002 00000056 00000000
> 
> Right, good. Thanks,

Thank you for reviewing!

> 
> > 
> > > > +		return 5;
> > > > +	return 6;
> > > > +}
> > > > +
> > > >  static int query_ddw(struct pci_dev *dev, const u32 *ddw_avail,
> > > > -			struct ddw_query_response *query)
> > > > +		     struct ddw_query_response *query,
> > > > +		     struct device_node *par_dn)
> > > >  {
> > > >  	struct device_node *dn;
> > > >  	struct pci_dn *pdn;
> > > > -	u32 cfg_addr;
> > > > +	u32 cfg_addr, query_out[5];
> > > >  	u64 buid;
> > > > -	int ret;
> > > > +	int ret, out_sz;
> > > >  
> > > >  	/*
> > > >  	 * Get the config address and phb buid of the PE window.
> > > > @@ -888,12 +906,29 @@ static int query_ddw(struct pci_dev *dev, const u32 *ddw_avail,
> > > >  	pdn = PCI_DN(dn);
> > > >  	buid = pdn->phb->buid;
> > > >  	cfg_addr = ((pdn->busno << 16) | (pdn->devfn << 8));
> > > > +	out_sz = query_ddw_out_sz(par_dn);
> > > > +
> > > > +	ret = rtas_call(ddw_avail[0], 3, out_sz, query_out,
> > > > +			cfg_addr, BUID_HI(buid), BUID_LO(buid));
> > > > +	dev_info(&dev->dev, "ibm,query-pe-dma-windows(%x) %x %x %x returned %d\n",
> > > > +		 ddw_avail[0], cfg_addr, BUID_HI(buid), BUID_LO(buid), ret);
> > > > +
> > > > +	switch (out_sz) {
> > > > +	case 5:
> > > > +		query->windows_available = query_out[0];
> > > > +		query->largest_available_block = query_out[1];
> > > > +		query->page_size = query_out[2];
> > > > +		query->migration_capable = query_out[3];
> > > > +		break;
> > > > +	case 6:
> > > > +		query->windows_available = query_out[0];
> > > > +		query->largest_available_block = ((u64)query_out[1] << 32) |
> > > > +						 query_out[2];
> > > > +		query->page_size = query_out[3];
> > > > +		query->migration_capable = query_out[4];
> > > > +		break;
> > > > +	}
> > > >  
> > > > -	ret = rtas_call(ddw_avail[0], 3, 5, (u32 *)query,
> > > > -		  cfg_addr, BUID_HI(buid), BUID_LO(buid));
> > > > -	dev_info(&dev->dev, "ibm,query-pe-dma-windows(%x) %x %x %x"
> > > > -		" returned %d\n", ddw_avail[0], cfg_addr, BUID_HI(buid),
> > > > -		BUID_LO(buid), ret);
> > > >  	return ret;
> > > >  }
> > > >  
> > > > @@ -1040,7 +1075,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
> > > >  	 * of page sizes: supported and supported for migrate-dma.
> > > >  	 */
> > > >  	dn = pci_device_to_OF_node(dev);
> > > > -	ret = query_ddw(dev, ddw_avail, &query);
> > > > +	ret = query_ddw(dev, ddw_avail, &query, pdn);
> > > >  	if (ret != 0)
> > > >  		goto out_failed;
> > > >  
> > > > @@ -1068,7 +1103,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
> > > >  	/* check largest block * page size > max memory hotplug addr */
> > > >  	max_addr = ddw_memory_hotplug_max();
> > > >  	if (query.largest_available_block < (max_addr >> page_shift)) {
> > > > -		dev_dbg(&dev->dev, "can't map partition max 0x%llx with %u "
> > > > +		dev_dbg(&dev->dev, "can't map partition max 0x%llx with %llu "
> > > >  			  "%llu-sized pages\n", max_addr,  query.largest_available_block,
> > > >  			  1ULL << page_shift);
> > > >  		goto out_failed;
> > > > 
> > 
> > Best regards,
> > Leonardo
> > 

Best regards,
Leonardo Bras