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

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Message-ID: <8c7b68fc-c275-45c3-830a-3ea3174f38f5@ti.com>
Date: Mon, 21 Apr 2025 13:29:47 +0530
From: "Kumar, Udit" <u-kumar1@...com>
To: Siddharth Vadapalli <s-vadapalli@...com>
CC: <nm@...com>, <vigneshr@...com>, <kristo@...nel.org>, <robh@...nel.org>,
        <krzk+dt@...nel.org>, <conor+dt@...nel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <srk@...com>,
        <u-kumar1@...com>
Subject: Re: [PATCH 2/7] arm64: dts: ti: k3-j7200-main: switch to 64-bit
 address space for PCIe1


On 4/20/2025 7:48 PM, Siddharth Vadapalli wrote:
> 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@...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@...0000 {
>>>>>     		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@...0000 {
>>>>>     		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'.

Thanks Siddharth,

I understand, you are enabling 64 bit addressing, keeping previous 
addressing scheme unchanged.

Since, you are changing, it will be good to give max possible addresses 
for 32 bits EP.

or

If you are saying , 32 bit EP has to be limited to 128MB then

Acked-by: Udit Kumar <u-kumar1@...com>

> Regards,
> Siddharth.