From: Arnd Bergmann <arnd@arndb.de>
To: Gabriele Paoloni <gabriele.paoloni@huawei.com>
Cc: "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "mark.rutland@arm.com" <mark.rutland@arm.com>,
        "catalin.marinas@arm.com" <catalin.marinas@arm.com>,
        "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
        "liviu.dudau@arm.com" <liviu.dudau@arm.com>,
        Linuxarm <linuxarm@huawei.com>,
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        "xuwei (O)" <xuwei5@hisilicon.com>,
        Jason Gunthorpe <jgunthorpe@obsidianresearch.com>,
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        "minyard@acm.org" <minyard@acm.org>,
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        John Garry <john.garry@huawei.com>, "olof@lixom.net" <olof@lixom.net>,
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        "bhelgaas@go og le.com" <bhelgaas@google.com>,
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        "zhichang.yuan02@gmail.com" <zhichang.yuan02@gmail.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Yuanzhichang <yuanzhichang@hisilicon.com>,
        "zourongrong@gmail.com" <zourongrong@gmail.com>
Subject: Re: [PATCH V5 3/3] ARM64 LPC: LPC driver implementation on Hip06
Date: Fri, 25 Nov 2016 13:03:33 +0100
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On Friday, November 25, 2016 8:46:11 AM CET Gabriele Paoloni wrote:
> > From: Arnd Bergmann [mailto:arnd@arndb.de]
> > 
> > On Wednesday, November 23, 2016 6:07:11 PM CET Arnd Bergmann wrote:
> > > On Wednesday, November 23, 2016 3:22:33 PM CET Gabriele Paoloni
> > wrote:
> > > > From: Arnd Bergmann [mailto:arnd@arndb.de]
> > > > > On Friday, November 18, 2016 5:03:11 PM CET Gabriele Paoloni
> >  /*
> > @@ -549,9 +548,14 @@ static int of_translate_one(struct device_node
> > *parent, struct of_bus *bus,
> >   * that translation is impossible (that is we are not dealing with a
> > value
> >   * that can be mapped to a cpu physical address). This is not really
> > specified
> >   * that way, but this is traditionally the way IBM at least do things
> > + *
> > + * Whenever the translation fails, the *host pointer will be set to
> > the
> > + * device that lacks a tranlation, and the return code is relative to
> > + * that node.
> 
> This seems to be wrong to me. We are abusing of the error conditions.
> So effectively if there is a buggy DT for an IO resource we end up
> assuming that we are using a special IO device with unmapped addresses.
> 
> The patch at the bottom apply on top of this one and I think is a more
> reasonable approach

It was meant as a logical extension to the existing interface,
translating the address as far as we can, and reporting back
how far we got.

Maybe we can return 'of_root' by instead of NULL to signify
that we have converted all the way to the root of the DT?
That would make it more consistent, but slightly more complicated
for the common case.

> >   */
> >  static u64 __of_translate_address(struct device_node *dev,
> > -				  const __be32 *in_addr, const char *rprop)
> > +				  const __be32 *in_addr, const char *rprop,
> > +				  struct device_node **host)
> >  {
> >  	struct device_node *parent = NULL;
> >  	struct of_bus *bus, *pbus;
> > @@ -564,6 +568,7 @@ static u64 __of_translate_address(struct
> > device_node *dev,
> >  	/* Increase refcount at current level */
> >  	of_node_get(dev);
> > 
> > +	*host = NULL;
> >  	/* Get parent & match bus type */
> >  	parent = of_get_parent(dev);
> >  	if (parent == NULL)
> > @@ -600,8 +605,9 @@ static u64 __of_translate_address(struct
> > device_node *dev,
> >  		pbus = of_match_bus(parent);
> >  		pbus->count_cells(dev, &pna, &pns);
> >  		if (!OF_CHECK_COUNTS(pna, pns)) {
> > -			pr_err("Bad cell count for %s\n",
> > -			       of_node_full_name(dev));
> > +			pr_debug("Bad cell count for %s\n",
> > +				 of_node_full_name(dev));
> > +			*host = of_node_get(parent);
> >  			break;
> >  		}
> > 
> > @@ -609,7 +615,9 @@ static u64 __of_translate_address(struct
> > device_node *dev,
> >  		    pbus->name, pna, pns, of_node_full_name(parent));
> > 
> >  		/* Apply bus translation */
> > -		if (of_translate_one(dev, bus, pbus, addr, na, ns, pna,
> > rprop))
> > +		result = of_translate_one(dev, bus, pbus, addr, na, ns,
> > +					  pna, rprop);
> > +		if (result == OF_BAD_ADDR)
> 
> It seems to me that here you missed "*host = of_node_get(parent);"..?
> 

Yes, Zhichang also pointed out the same thing, this is not
right yet. My thought was that we need to check the #address-cells
and #size-cells of the parent node and return if they are not set,
but the bus should really have those.

What we need to do instead is check the "ranges" of the parent
and fail if there is no translation. Simply setting the host
here however won't work either because that leads to returning
OF_BAD_ADDR.


> >  		/* Complete the move up one level */
> > @@ -628,13 +636,32 @@ static u64 __of_translate_address(struct
> > device_node *dev,
> > 
> >  u64 of_translate_address(struct device_node *dev, const __be32
> > *in_addr)
> >  {
> > -	return __of_translate_address(dev, in_addr, "ranges");
> > +	struct device_node *host;
...
> > +
> >  phys_addr_t pci_pio_to_address(unsigned long pio)
> >  {
> >  	phys_addr_t address = (phys_addr_t)OF_BAD_ADDR;
> > diff --git a/include/linux/pci.h b/include/linux/pci.h
> > index 6bd94a803e8f..b7a8fa3da3ca 100644
> > --- a/include/linux/pci.h
> > +++ b/include/linux/pci.h
> > @@ -1192,7 +1192,8 @@ int __must_check pci_bus_alloc_resource(struct
> > pci_bus *bus,
> >  			void *alignf_data);

[Many lines of reply trimmed here, please make sure you don't quote too
much context when you reply, it's really annoying to read through
it otherwise]

>  /*
> + * of_isa_indirect_io - get the IO address from some isa reg property value.
> + *	For some isa/lpc devices, no ranges property in ancestor node.
> + *	The device addresses are described directly in their regs property.
> + *	This fixup function will be called to get the IO address of isa/lpc
> + *	devices when the normal of_translation failed.
> + *
> + * @parent:	points to the parent dts node;
> + * @bus:		points to the of_bus which can be used to parse address;
> + * @addr:	the address from reg property;
> + * @na:		the address cell counter of @addr;
> + * @presult:	store the address paresed from @addr;
> + *
> + * return 1 when successfully get the I/O address;
> + * 0 will return for some failures.
> + */
> +static int of_get_isa_indirect_io(struct device_node *parent,
> +				struct of_bus *bus, __be32 *addr,
> +				int na, u64 *presult)
> +{
> +	unsigned int flags;
> +	unsigned int rlen;
> +
> +	/* whether support indirectIO */
> +	if (!indirect_io_enabled())
> +		return 0;
> +
> +	if (!of_bus_isa_match(parent))
> +		return 0;
> +
> +	flags = bus->get_flags(addr);
> +	if (!(flags & IORESOURCE_IO))
> +		return 0;
> +
> +	/* there is ranges property, apply the normal translation directly. */
> +	if (of_get_property(parent, "ranges", &rlen))
> +		return 0;
> +
> +	*presult = of_read_number(addr + 1, na - 1);
> +	/* this fixup is only valid for specific I/O range. */
> +	return addr_is_indirect_io(*presult);
> +}

Right, this would work. The reason I didn't go down this route is
that I wanted to keep it generic enough to allow doing the same
for PCI host bridges with a nonlinear mapping of the I/O space.

There isn't really anything special about ISA here, other than the
fact that the one driver that needs it happens to be for ISA rather
than PCI.

> +/*
>   * Translate an address from the device-tree into a CPU physical address,
>   * this walks up the tree and applies the various bus mappings on the
>   * way.
> @@ -600,14 +643,23 @@ static u64 __of_translate_address(struct device_node *dev,
>  			result = of_read_number(addr, na);
>  			break;
>  		}
> +		/*
> +		 * For indirectIO device which has no ranges property, get
> +		 * the address from reg directly.
> +		 */
> +		if (of_get_isa_indirect_io(dev, bus, addr, na, &result)) {
> +			pr_debug("isa indirectIO matched(%s)..addr = 0x%llx\n",
> +				of_node_full_name(dev), result);
> +			*host = of_node_get(parent);
> +			break;
> +		}
>  

If we do the special case for ISA as you suggest above, I would still want
to keep it in of_translate_ioport(), I think that's a useful change by
itself in my patch.

	Arnde