On 10/15/21 14:15, Jessica Clarke wrote:

On 15 Oct 2021, at 12:54, Heinrich Schuchardt [off-list ref] wrote:

quoted

On 10/15/21 12:14, Bin Meng wrote:

quoted

On Fri, Oct 15, 2021 at 6:09 PM Heinrich Schuchardt
[off-list ref] wrote:

quoted

The CLINT in the T-HEAD 9xx processors do not support 64bit mmio access to
the MTIMER device. The current schema does not allow to specify this.

OpenSBI currently uses a property 'clint,has-no-64bit-mmio' to indicate the
restriction. Samuael Holland suggested in
lib: utils/timer: Use standard property to specify 32-bit I/O
https://github.com/smaeul/opensbi/commit/b95e9cf7cf93b0af16fc89204378bc59ff30008e
to use "reg-io-width = <4>;" as the reg-io-width property is generally used
in the devicetree schema for such a condition.

A release candidate of the ACLINT specification is available at
https://github.com/riscv/riscv-aclint/releases

Add reg-io-width as optional property to the SiFive Core Local Interruptor.

Signed-off-by: Heinrich Schuchardt <redacted>
---
  Documentation/devicetree/bindings/timer/sifive,clint.yaml | 7 +++++++
  1 file changed, 7 insertions(+)

diff --git a/Documentation/devicetree/bindings/timer/sifive,clint.yaml b/Documentation/devicetree/bindings/timer/sifive,clint.yaml
index a35952f48742..266012d887b5 100644
--- a/Documentation/devicetree/bindings/timer/sifive,clint.yaml
+++ b/Documentation/devicetree/bindings/timer/sifive,clint.yaml

@@ -41,6 +41,13 @@ properties:
    reg:
      maxItems: 1

+  reg-io-width:
+    description: |
+      Some CLINT implementations, e.g. on the T-HEAD 9xx, only support
+      32bit access for MTIMER.
+    $ref: /schemas/types.yaml#/definitions/uint32
+    const: 4

But this is not a "sifive,clint" anyway. Should there be a new
dt-bindings for T-Head clint variant?

I assume by new dt-bindings variant you mean: Add a new compatible string in Documentation/devicetree/bindings/timer/sifive,clint.yaml.

The vendor Debian image uses:
compatible = "{allwinner,sun20i-d1-clint", "sifive,clint0”};

I assume Bin means to stop calling it a sifive,clint0 and instead have
something like

     "allwinner,sun20i-d1-clint", "thead,clint0"

as is being done for their non-conforming PLIC. It’s worth pointing out
that the same is true here; the SiFive CLINT supports 64-bit accesses
on RV64, so this is not compatible with a SiFive CLINT. Moreover, the
RISC-V spec was clearly written in a way that intended 64-bit accesses
to be supported for RV64, though was not completely explicit about
that, which has now been resolved (see
https://github.com/riscv/riscv-isa-manual/issues/639), so this CLINT
violates the obvious intent of the pre-1.12 privileged specs (see
Andrew’s message in the issue, which agrees with my reading).

Jess

This comment is referring to the discussion in

https://lore.kernel.org/lkml/693a609c-4278-84ab-8a9b-448936bb13d0@sholland.org/ (local)