[query] how to use "ranges" in device tree

[query] how to use "ranges" in device tree

[Jisheng Zhang]

Hi all,

I didn't fully understand the "ranges" usage, here is one situation which I dunno
how to handle.

In arch/arm/boot/dts/berlin2q.dtsi, we describe the /soc ranges as

ranges = <0 0xf7000000 0x1000000>;

That's fine. Now there's a pci device based on pcie-designware.c which prefer
put "config" space in reg. But the config space starts at 0xe0000000, due to
the /soc ranges, the "config" space following pcie node is not correct in fact.

soc {
	ranges = <0 0xf7000000 0x1000000>;
	...
	pcie: pcie at e40000 {
		compatible = "...";
		reg = <0xe40000 0x10000>, <0xe0000000 0x8000000>;
		reg-names = "dbi", "pad", "config";
		...
	};
	...
};

How to define the "config" space in this situation? Did we need to change
the /soc ranges as the following?

soc {
	ranges;
}

Thanks in advance,
Jisheng

[query] how to use "ranges" in device tree

[Jaehoon Chung]

Hi,

Well, I'm not sure..
But in my understanding..configuration range might be support both "ranges" and "config" of reg.

On 04/16/2015 10:59 PM, Jisheng Zhang wrote:
> Hi all,
> 
> I didn't fully understand the "ranges" usage, here is one situation which I dunno
> how to handle.
> 
> In arch/arm/boot/dts/berlin2q.dtsi, we describe the /soc ranges as
> 
> ranges = <0 0xf7000000 0x1000000>;
> 
> That's fine. Now there's a pci device based on pcie-designware.c which prefer
> put "config" space in reg. But the config space starts at 0xe0000000, due to
> the /soc ranges, the "config" space following pcie node is not correct in fact.
> 
> soc {
> 	ranges = <0 0xf7000000 0x1000000>;
> 	...
> 	pcie: pcie at e40000 {
> 		compatible = "...";
> 		reg = <0xe40000 0x10000>, <0xe0000000 0x8000000>;
> 		reg-names = "dbi", "pad", "config";
> 		...
> 	};
> 	...
> };

According to yours,

reg = <0xe40000 0x1000		/* dbi */
	0xe000000 0x800000	/* pad */
	0xf7000000 0x1000000>;	/* config ? */

If there is not "config" into reg-names, it should be tried to find it into "ranges".

If my understanding is wrong, let me know, plz.

In my case,

	reg = <0x156b0000 0x1000
		0x15680000 0x1000
		0x0c000000 0x1000>;
	reg-names = "elbi", "phy", "config";

	ranges = < ..... /* downstream I/O */
		  ...... /* non-prefetchable memory */


Best Regards,
Jaehoon Chung	

> 
> How to define the "config" space in this situation? Did we need to change
> the /soc ranges as the following?
> 
> soc {
> 	ranges;
> }
> 
> Thanks in advance,
> Jisheng
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 

[query] how to use "ranges" in device tree

[Jisheng Zhang]

Hi Jaehoon,

On Thu, 16 Apr 2015 15:59:45 -0700
Jaehoon Chung <jh80.chung@samsung.com> wrote:

> Hi,
> 
> Well, I'm not sure..
> But in my understanding..configuration range might be support both "ranges" and "config" of reg.
> 
> On 04/16/2015 10:59 PM, Jisheng Zhang wrote:
> > Hi all,
> > 
> > I didn't fully understand the "ranges" usage, here is one situation which I dunno
> > how to handle.
> > 
> > In arch/arm/boot/dts/berlin2q.dtsi, we describe the /soc ranges as
> > 
> > ranges = <0 0xf7000000 0x1000000>;
> > 
> > That's fine. Now there's a pci device based on pcie-designware.c which prefer
> > put "config" space in reg. But the config space starts at 0xe0000000, due to
> > the /soc ranges, the "config" space following pcie node is not correct in fact.
> > 
> > soc {
> > 	ranges = <0 0xf7000000 0x1000000>;
> > 	...
> > 	pcie: pcie at e40000 {
> > 		compatible = "...";
> > 		reg = <0xe40000 0x10000>, <0xe0000000 0x8000000>;
> > 		reg-names = "dbi", "pad", "config";
> > 		...
> > 	};
> > 	...
> > };
> 
> According to yours,
> 
> reg = <0xe40000 0x1000		/* dbi */
> 	0xe000000 0x800000	/* pad */
> 	0xf7000000 0x1000000>;	/* config ? */

oops, there's no pad at all, dbi starts at 0xf7e40000, config space starts at 0xe0000000

so my pcie in my understanding is

pcie: pcie at e40000 {
	compatible = "...";
	reg = <0xe40000 0x10000>, <0xe0000000 0x8000000>;
	reg-names = "dbi", "config";
};

But the "/soc" ranges is defined as "<0 0xf7000000 0x1000000>;", so the config space
in the above dts is not correct.

My solution is change the "/soc" ranges as following:

soc {
	ranges;
	...
};

Is there any elegant solutions for this situation?

> 
> If there is not "config" into reg-names, it should be tried to find it into "ranges".

The pcie-designware driver prefers users define config space in "reg"

Thanks for your help,
Jisheng

> 
> If my understanding is wrong, let me know, plz.
> 
> In my case,
> 
> 	reg = <0x156b0000 0x1000
> 		0x15680000 0x1000
> 		0x0c000000 0x1000>;
> 	reg-names = "elbi", "phy", "config";
> 
> 	ranges = < ..... /* downstream I/O */
> 		  ...... /* non-prefetchable memory */
> 
> 
> Best Regards,
> Jaehoon Chung	
> 
> > 
> > How to define the "config" space in this situation? Did we need to change
> > the /soc ranges as the following?
> > 
> > soc {
> > 	ranges;
> > }
> > 
> > Thanks in advance,
> > Jisheng
> > 
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel at lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> > 
> 

[query] how to use "ranges" in device tree

[Jisheng Zhang]

Hi all,

I got the solution, the ranges can define two or more ranges. What I need to do
is just add ranges for 0xe0000000 - 0xf0000000 as the following:

soc {
	ranges = <0 0xf7000000 0x1000000
		  0xe0000000 0xe0000000 0x10000000>;  //add this line
	...
	pcie: pcie at e40000 {
		...
		reg = <0xe40000 0x10000>, <0xe0000000 0x8000000>;
		reg-names = "dbi", "pad", "config";
		...
	};
}

Now, we can get the config space correctly.


Thanks,
Jisheng

On Thu, 16 Apr 2015 19:24:13 -0700
Jisheng Zhang <jszhang@marvell.com> wrote:

> Hi Jaehoon,
> 
> On Thu, 16 Apr 2015 15:59:45 -0700
> Jaehoon Chung <jh80.chung@samsung.com> wrote:
> 
> > Hi,
> > 
> > Well, I'm not sure..
> > But in my understanding..configuration range might be support both "ranges" and "config" of reg.
> > 
> > On 04/16/2015 10:59 PM, Jisheng Zhang wrote:
> > > Hi all,
> > > 
> > > I didn't fully understand the "ranges" usage, here is one situation which I dunno
> > > how to handle.
> > > 
> > > In arch/arm/boot/dts/berlin2q.dtsi, we describe the /soc ranges as
> > > 
> > > ranges = <0 0xf7000000 0x1000000>;
> > > 
> > > That's fine. Now there's a pci device based on pcie-designware.c which prefer
> > > put "config" space in reg. But the config space starts at 0xe0000000, due to
> > > the /soc ranges, the "config" space following pcie node is not correct in fact.
> > > 
> > > soc {
> > > 	ranges = <0 0xf7000000 0x1000000>;
> > > 	...
> > > 	pcie: pcie at e40000 {
> > > 		compatible = "...";
> > > 		reg = <0xe40000 0x10000>, <0xe0000000 0x8000000>;
> > > 		reg-names = "dbi", "pad", "config";
> > > 		...
> > > 	};
> > > 	...
> > > };
> > 
> > According to yours,
> > 
> > reg = <0xe40000 0x1000		/* dbi */
> > 	0xe000000 0x800000	/* pad */
> > 	0xf7000000 0x1000000>;	/* config ? */
> 
> oops, there's no pad at all, dbi starts at 0xf7e40000, config space starts at 0xe0000000
> 
> so my pcie in my understanding is
> 
> pcie: pcie at e40000 {
> 	compatible = "...";
> 	reg = <0xe40000 0x10000>, <0xe0000000 0x8000000>;
> 	reg-names = "dbi", "config";
> };
> 
> But the "/soc" ranges is defined as "<0 0xf7000000 0x1000000>;", so the config space
> in the above dts is not correct.
> 
> My solution is change the "/soc" ranges as following:
> 
> soc {
> 	ranges;
> 	...
> };
> 
> Is there any elegant solutions for this situation?
> 
> > 
> > If there is not "config" into reg-names, it should be tried to find it into "ranges".
> 
> The pcie-designware driver prefers users define config space in "reg"
> 
> Thanks for your help,
> Jisheng
> 
> > 
> > If my understanding is wrong, let me know, plz.
> > 
> > In my case,
> > 
> > 	reg = <0x156b0000 0x1000
> > 		0x15680000 0x1000
> > 		0x0c000000 0x1000>;
> > 	reg-names = "elbi", "phy", "config";
> > 
> > 	ranges = < ..... /* downstream I/O */
> > 		  ...... /* non-prefetchable memory */
> > 
> > 
> > Best Regards,
> > Jaehoon Chung	
> > 
> > > 
> > > How to define the "config" space in this situation? Did we need to change
> > > the /soc ranges as the following?
> > > 
> > > soc {
> > > 	ranges;
> > > }
> > > 
> > > Thanks in advance,
> > > Jisheng
> > > 
> > > _______________________________________________
> > > linux-arm-kernel mailing list
> > > linux-arm-kernel at lists.infradead.org
> > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> > > 
> > 
> 

[query] how to use "ranges" in device tree

[Arnd Bergmann]

On Friday 17 April 2015 11:50:16 Jisheng Zhang wrote:
> Hi all,
> 
> I got the solution, the ranges can define two or more ranges. What I need to do
> is just add ranges for 0xe0000000 - 0xf0000000 as the following:
> 
> soc {
>         ranges = <0 0xf7000000 0x1000000
>                   0xe0000000 0xe0000000 0x10000000>;  //add this line
>         ...
>         pcie: pcie at e40000 {
>                 ...
>                 reg = <0xe40000 0x10000>, <0xe0000000 0x8000000>;
>                 reg-names = "dbi", "pad", "config";
>                 ...
>         };
> }
> 
> Now, we can get the config space correctly.
> 

This will work correctly, but it is not a very clean solution, because
you define an intermediate address space that has some part of the
bus mapped to zero, and another part mapped to a high address that
matches the address the CPU sees.

A nicer (but a little more complicated) way to do this would be to use
#address-cells=<2> in the parent bus and use that to enumerate the
address ranges that get passed through:

soc {
	#address-cells=<2>;
	#size-cells=<1>;
        ranges = <0 0  0xf7000000  0x1000000>, /* 0: the normal regs */
		  <1 0  0xe0000000 0x16000000>; /* 1: reallocated registers for PCI */

	pcie at e40000 {
		#address-cells = <3>;
		#size-cells = <2>;
		reg = <0 0xe40000 0x10000>, <1 0 0x8000000>;

		/* memory space at pci address 0xf0000000, cpu address 0xf0000000, 
		   bus address 0x10000000 */
		ranges = <0x02000000 0 0xf0000000   0 0x10000000   0 0x06000000>;
	};

	...
};

The ranges property inside of the pcie node here should match whatever you program
into the inbound mapping registers of the PCIe host controller (if any).

	Arnd

[query] how to use "ranges" in device tree

[Jisheng Zhang]

Dear Arnd,

On Fri, 17 Apr 2015 01:32:00 -0700
Arnd Bergmann <arnd@arndb.de> wrote:

> On Friday 17 April 2015 11:50:16 Jisheng Zhang wrote:
> > Hi all,
> > 
> > I got the solution, the ranges can define two or more ranges. What I need to do
> > is just add ranges for 0xe0000000 - 0xf0000000 as the following:
> > 
> > soc {
> >         ranges = <0 0xf7000000 0x1000000
> >                   0xe0000000 0xe0000000 0x10000000>;  //add this line
> >         ...
> >         pcie: pcie at e40000 {
> >                 ...
> >                 reg = <0xe40000 0x10000>, <0xe0000000 0x8000000>;
> >                 reg-names = "dbi", "pad", "config";
> >                 ...
> >         };
> > }
> > 
> > Now, we can get the config space correctly.
> > 
> 
> This will work correctly, but it is not a very clean solution, because
> you define an intermediate address space that has some part of the
> bus mapped to zero, and another part mapped to a high address that
> matches the address the CPU sees.

Seems I had a better understanding of the "ranges" usage, thanks for
your explanation. 

> 
> A nicer (but a little more complicated) way to do this would be to use
> #address-cells=<2> in the parent bus and use that to enumerate the

In this way, we need to change all device nodes' "reg" in arch/arm/boot/dts/berlin2q.dtsi?
And in arm64 case, we should use #address-cells=<3>?

If above two answer is yes, setting "ranges = <..>" seems add complexity in my
humble opinion. So is it better to use 1:1 mapping by "ranges;" in "/soc" node?

Thanks a lot,
Jisheng

> address ranges that get passed through:
> 
> soc {
> 	#address-cells=<2>;
> 	#size-cells=<1>;
>         ranges = <0 0  0xf7000000  0x1000000>, /* 0: the normal regs */
> 		  <1 0  0xe0000000 0x16000000>; /* 1: reallocated registers for PCI */
> 
> 	pcie at e40000 {
> 		#address-cells = <3>;
> 		#size-cells = <2>;
> 		reg = <0 0xe40000 0x10000>, <1 0 0x8000000>;
> 
> 		/* memory space at pci address 0xf0000000, cpu address 0xf0000000, 
> 		   bus address 0x10000000 */
> 		ranges = <0x02000000 0 0xf0000000   0 0x10000000   0 0x06000000>;
> 	};
> 
> 	...
> };
> 
> The ranges property inside of the pcie node here should match whatever you program
> into the inbound mapping registers of the PCIe host controller (if any).
> 
> 	Arnd

[query] how to use "ranges" in device tree

[Arnd Bergmann]

On Friday 17 April 2015 16:45:46 Jisheng Zhang wrote:
> > 
> > A nicer (but a little more complicated) way to do this would be to use
> > #address-cells=<2> in the parent bus and use that to enumerate the
> 
> In this way, we need to change all device nodes' "reg" in arch/arm/boot/dts/berlin2q.dtsi?

Correct

> And in arm64 case, we should use #address-cells=<3>?

It depends: if any of the address spaces within are 64-bit wide, yes, otherwise
you can make the virtual spaces just 2-cell wide.

> If above two answer is yes, setting "ranges = <..>" seems add complexity in my
> humble opinion. So is it better to use 1:1 mapping by "ranges;" in "/soc" node?
 
I agree, it gets a little awkward at that point. A better solution here would
be to take the PCI node out of /soc and move it to the root node. This has
the slight downside that you end up with registers being part of /soc and /pci,
but that's perfectly legal.

	Arnd

[query] how to use "ranges" in device tree

[Sebastian Hesselbarth]

On 17.04.2015 05:50, Jisheng Zhang wrote:
> I got the solution, the ranges can define two or more ranges. What I need to do
> is just add ranges for 0xe0000000 - 0xf0000000 as the following:

Jisheng,

the beauty of ranges property often reminds me of perl code: once you
stop looking at it, you cannot recall how you did it nor how that
has ever worked.

What the ranges property does is to map an address range back to the
address space of the parent node. In this case, the parent node of
"soc" is the root node with "ranges;", i.e. 1:1 mapping.

> soc {
> 	ranges = <0 0xf7000000 0x1000000

The line above maps 0x1000000 bytes starting@0 back to 0xf7000000
of the parent node's address space. This allows us to leave the 0xf7
prefix for each of the internal bus nodes below.

> 		  0xe0000000 0xe0000000 0x10000000>;  //add this line

You could have chosen any address as the first value that does not
interfere with 0x0-0x1000000 of the first range, e.g.

0x20000000 0xe0000000 0x10000000

would allow you to access the pcie memory space at 0x20000000 in nodes
below that ranges property.

Sebastian

> 	pcie: pcie at e40000 {
> 		...
> 		reg = <0xe40000 0x10000>, <0xe0000000 0x8000000>;
> 		reg-names = "dbi", "pad", "config";
> 		...
> 	};
> }
>
> Now, we can get the config space correctly.

[query] how to use "ranges" in device tree

[Jisheng Zhang]

On Fri, 17 Apr 2015 01:38:16 -0700
Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com> wrote:

> On 17.04.2015 05:50, Jisheng Zhang wrote:
> > I got the solution, the ranges can define two or more ranges. What I need to do
> > is just add ranges for 0xe0000000 - 0xf0000000 as the following:
> 
> Jisheng,
> 
> the beauty of ranges property often reminds me of perl code: once you
> stop looking at it, you cannot recall how you did it nor how that
> has ever worked.
> 
> What the ranges property does is to map an address range back to the
> address space of the parent node. In this case, the parent node of
> "soc" is the root node with "ranges;", i.e. 1:1 mapping.
> 
> > soc {
> > 	ranges = <0 0xf7000000 0x1000000
> 
> The line above maps 0x1000000 bytes starting at 0 back to 0xf7000000
> of the parent node's address space. This allows us to leave the 0xf7
> prefix for each of the internal bus nodes below.
> 
> > 		  0xe0000000 0xe0000000 0x10000000>;  //add this line
> 
> You could have chosen any address as the first value that does not
> interfere with 0x0-0x1000000 of the first range, e.g.
> 
> 0x20000000 0xe0000000 0x10000000
> 
> would allow you to access the pcie memory space at 0x20000000 in nodes
> below that ranges property.
> 

Thanks for this explanation which gives me good guide about the "ranges" usage.

> 
> > 	pcie: pcie at e40000 {
> > 		...
> > 		reg = <0xe40000 0x10000>, <0xe0000000 0x8000000>;
> > 		reg-names = "dbi", "pad", "config";
> > 		...
> > 	};
> > }
> >
> > Now, we can get the config space correctly.
>