Re: [PATCH 2/7] arm64: dts: ti: k3-j7200-main: switch to 64-bit address space for PCIe1

[Siddharth Vadapalli <s-vadapalli@ti.com>]

On Sun, Apr 20, 2025 at 10:17:46AM +0530, Kumar, Udit wrote:
> Hello Siddharth
> 
> On 4/20/2025 8:33 AM, Siddharth Vadapalli wrote:
> > On Sat, Apr 19, 2025 at 11:35:50PM +0530, Kumar, Udit wrote:
> > 
> > Hello Udit,
> > 
> > > On 4/17/2025 5:34 PM, Siddharth Vadapalli wrote:
> > > > The PCIe0 instance of PCIe in J7200 SoC supports:
> > > > 1. 128 MB address region in the 32-bit address space
> > > > 2. 4 GB address region in the 64-bit address space
> > > > 
> > > > The default configuration is that of a 128 MB address region in the
> > > > 32-bit address space. While this might be sufficient for most use-cases,
> > > > it is insufficient for supporting use-cases which require larger address
> > > > spaces. Therefore, switch to using the 64-bit address space with a 4 GB
> > > > address region.
> > > > 
> > > > Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
> > > > ---
> > > >    arch/arm64/boot/dts/ti/k3-j7200-main.dtsi | 7 ++++---
> > > >    1 file changed, 4 insertions(+), 3 deletions(-)
> > > > 
> > > > diff --git a/arch/arm64/boot/dts/ti/k3-j7200-main.dtsi b/arch/arm64/boot/dts/ti/k3-j7200-main.dtsi
> > > > index 5ab510a0605f..e898dffdebbe 100644
> > > > --- a/arch/arm64/boot/dts/ti/k3-j7200-main.dtsi
> > > > +++ b/arch/arm64/boot/dts/ti/k3-j7200-main.dtsi
> > > > @@ -759,7 +759,7 @@ pcie1_rc: pcie@2910000 {
> > > >    		reg = <0x00 0x02910000 0x00 0x1000>,
> > > >    		      <0x00 0x02917000 0x00 0x400>,
> > > >    		      <0x00 0x0d800000 0x00 0x00800000>,
> > > > -		      <0x00 0x18000000 0x00 0x00001000>;
> > > > +		      <0x41 0x00000000 0x00 0x00001000>;
> > > >    		reg-names = "intd_cfg", "user_cfg", "reg", "cfg";
> > > >    		interrupt-names = "link_state";
> > > >    		interrupts = <GIC_SPI 330 IRQ_TYPE_EDGE_RISING>;
> > > > @@ -778,8 +778,9 @@ pcie1_rc: pcie@2910000 {
> > > >    		device-id = <0xb00f>;
> > > >    		msi-map = <0x0 &gic_its 0x0 0x10000>;
> > > >    		dma-coherent;
> > > > -		ranges = <0x01000000 0x0 0x18001000  0x00 0x18001000  0x0 0x0010000>,
> > > > -			 <0x02000000 0x0 0x18011000  0x00 0x18011000  0x0 0x7fef000>;
> > > > +		ranges = <0x01000000 0x00 0x00001000 0x41 0x00001000 0x00 0x00100000>, /* IO (1 MB) */
> > > > +			 <0x02000000 0x00 0x00101000 0x41 0x00101000 0x00 0x08000000>, /* 32-bit Non-Prefetchable MEM (128 MB) */
> > > > +			 <0x43000000 0x41 0x08101000 0x41 0x08101000 0x00 0xf7eff000>; /* 64-bit Prefetchable MEM (4 GB - (129 MB + 4 KB)) */
> > > Sorry for novice question,
> > > 
> > > with this change,  How do you see  old EP working which supports 32 bit
> > > addressing,
> > > 
> > > or some translation is possible ?
> > > 
> > > 0x43000000 0x41 0x08101000 0x41 0x08101000 0x00 0xf7eff000>
> > > 
> > > to
> > > 
> > > 0x63000000 0x00 0x08101000 0x41 0x08101000 0x00 0xf7eff000>
> > I didn't understand the question completely, but I shall try to explain
> > the changes being made which might possibly answer your question.
> 
> If I understood well then what you are doing here
> 
> 0x43000000 0x41 0x08101000 0x41 0x08101000 0x00 0xf7eff000>
> 
> PCIe address
> 0x43000000 0x41 0x08101000 -->
> Property 0x43
> 0x43 as npt000ss ->relocatable, prefetch and 64 Bit memory space PCIe Bus address  0x41 0x08101000
> CPU address space 0x41 0x08101000
> This will work fine, if EP supports 64 bit addressing scheme.
> 
> In case, we want to work with EP of 32 Bit, Then do you see , we need to relocate PCIe (lower 32 bits) to CPU address (64 bits)

A total of 3 Address Regions have been defined:
1. 1 MB IO in the 32-bit PCIe Bus Address Space
2. 128 MB Non-Prefetchable MEM in the 32-bit PCIe Bus Address Space
3. (4 GB - 129 MB - 4 KB) Prefetchable MEM in the 64-bit PCIe Bus
Address Space

'1' and '2' above provide backward compatibility with Endpoint Devices
that can only support 32-bit PCIe Bus Addressing. The __newly__ added
'3' enables Endpoint Devices that support 64-bit PCIe Bus Addressing to
claim larger Memory Address Space on top of what is supported by '1' and
'2'.

Regards,
Siddharth.