Re: [PATCH v2 0/6] spacemit: k3: Replace bad CLINT node with ACLINT nodes

[Junhui Liu]

Hi Bo,

On Fri Sep 11, 2026 at 4:43 PM CST, Bo Gan wrote:
> Hi Junhui,
>
> Thanks for your patch. This would give me more clarity while reviewing
> the OpenSBI patchset from Troy, and I was wondering why Troy sent this
> https://lore.kernel.org/opensbi/20260908-ipi-clear-all-v1-1-b1bd5d016eb6@xxxxxxxxx/T/#u
>
> Now it's much clearer -- K3 has two ways to do IPI, ACLINT and IMSIC.
>
> One thing that may help us further: Can you clarify on the exact meaning
> of "M-mode only"? OpenSBI would use PMP to protect those MSWI/MTIMER
> regions, so I wonder if you meant that it's enforced by the PMP settings,
> or it's *actually* enforced by the device itself (or fabric)? AFAIK, to
> achieve this, the device must have a way to distinguish the privilege-
> level of the CPU at the time it initiated the MMIO request. Hence, the
> core must be putting the privilege level as some kind of attribute in the
> MMIO request. Is that the case in k3? Can you confirm with SpacemiT?

Thanks for pointing this out. I have double-checked and found that my
earlier "M-mode only" description was incorrect. The restriction depends
on the eFuse configuration rather than CPU privilege modes. Under the
relevant eFuse configuration, the non-secure address window becomes
inaccessible, while the secure window remains available. PMP handles
access restrictions based on privilege mode.

I also verified that S-mode can read MSIP and MTIME through the secure
window once PMP allows those reads.

I will correct the explanation and use the secure address window
consistently for all ACLINT components in the next version.

>
> On 9/8/26 09:28, Junhui Liu wrote:
>> When testing OpenSBI with the upstream Device Tree, the CLINT controller
>> failed to function properly with the irqchip.riscv_imsic_noipi boot
>> parameter:
>> 
>>    Platform IPI Device         : aclint-mswi
>>    Platform Timer Device       : aclint-mtimer @ 24000000Hz
>>    
>>    Domain0 Region03            : 0x00000000e081c000-0x00000000e081ffff M: (I,R,W) S/U: ()
>>    
>>    [    0.091014] smp: Bringing up secondary CPUs ...
>>    [   10.104917] CPU1 failed to report alive state
>>    [   20.118689] CPU2 failed to report alive state
>>    [   30.132288] CPU3 failed to report alive state
>>    [   40.145953] CPU4 failed to report alive state
>>    [   50.159604] CPU5 failed to report alive state
>>    [   60.173212] CPU6 failed to report alive state
>>    [   70.186981] CPU7 failed to report alive state
>>    [   70.191411] smp: Brought up 1 node, 1 CPU
>> 
>> Through exploring and testing, I discovered that the K3 actually
>> provides all three complete ACLINT components, and subsequent
>> confirmation with the vendor yielded the following information:
>> 
>> The ACLINT controllers are mapped to two physical memory regions:
>> secure (0xf1810000-0xf1820000) and non-secure (0xe0810000-0xe0820000),
>> with varying accessibility per controller and execution mode:
>> 
>> +---------+--------+------------------------+-----------------------+
>> | Offset  | Module | Secure Region          | Non-Secure Region     |
>> +---------+--------+------------------------+-----------------------+
>> | +0x0000 | MSWI   | 0xf1810000-0xf1813fff  | 0xe0810000-0xe0813fff |
>> |         |        | (M-mode only)          | (Inaccessible)        |
>> +---------+--------+------------------------+-----------------------+
>> | +0x4000 | MTIMER | 0xf1814000-0xf181bfff  | 0xe0814000-0xe081bfff |
>> |         |        | (M-mode only)          | (Inaccessible)        |
>> +---------+--------+------------------------+-----------------------+
>> | +0xc000 | SSWI   | 0xf181c000-0xf181ffff  | 0xe081c000-0xe081ffff |
>> |         |        | (M-mode only if efused)| (M/S-mode Accessible) |
>> +---------+--------+------------------------+-----------------------+
>> 
>> Taking these constraints into account, we choose the secure region
>> (0xf1810000-0xf181bfff) for the M-mode ACLINT components (MSWI and
>> MTIMER), and the non-secure region (0xe081c000-0xe081ffff) for the
>> S-mode SSWI component.
>> 
>> Signed-off-by: Junhui Liu <junhui.liu@xxxxxxxxxxxxx>
>> ---
>> Changes in v2:
>> - Drop the generic riscv,aclint-* fallback compatibles and use only
>>    SpacemiT K3-specific compatibles.
>> - Match spacemit,k3-aclint-sswi directly in the SSWI driver.
>> - Squash the ACLINT MSWI and MTIMER DT additions into the patch that
>>    replaces the incorrect CLINT node.
>> - Link to v1: https://patch.msgid.link/20260729-k3-aclint-v1-0-aef88614d3a5@xxxxxxxxxxxxx
>> 
>> ---
>> Junhui Liu (6):
>>        dt-bindings: timer: thead,c900-aclint-mtimer: Add SpacemiT K3
>>        dt-bindings: interrupt-controller: thead,c900-aclint-mswi: Add SpacemiT K3
>>        dt-bindings: interrupt-controller: thead,c900-aclint-sswi: Add SpacemiT K3
>>        dt-bindings: timer: sifive,clint: Deprecate spacemit,k3-clint
>>        irqchip/aclint-sswi: Add support for SpacemiT K3
>>        riscv: dts: spacemit: k3: Replace incorrect CLINT node with ACLINT nodes
>> 
>>   .../thead,c900-aclint-mswi.yaml                    |  1 +
>>   .../thead,c900-aclint-sswi.yaml                    |  5 +--
>>   .../devicetree/bindings/timer/sifive,clint.yaml    |  5 ++-
>>   .../bindings/timer/thead,c900-aclint-mtimer.yaml   |  1 +
>>   arch/riscv/boot/dts/spacemit/k3.dtsi               | 37 ++++++++++++++++------
>>   drivers/irqchip/irq-aclint-sswi.c                  |  1 +
>>   6 files changed, 37 insertions(+), 13 deletions(-)
>> ---
>> base-commit: cee9395acd8043be0644b25c34bfa86623f2b935
>> change-id: 20260729-k3-aclint-94ca9d3f818f
>> 
>> Best regards,
>> --
>> Junhui Liu <junhui.liu@xxxxxxxxxxxxx>
>> 
>> 
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>
> Bo

-- 
Best regards,
Junhui Liu