linux-kernel - Re: [PATCH v2 1/2] dt-bindings: remoteproc: Add C906L rproc for Sophgo CV1800B SoC

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Message-ID: <bfvsmafcsxy4gr4dsprn4z4yl2lltgje2oilsny7vanb7rsolq@t2prbsfisioc>
Date: Wed, 30 Jul 2025 14:05:40 +0800
From: Inochi Amaoto <inochiama@...il.com>
To: Junhui Liu <junhui.liu@...moral.tech>, 
	Inochi Amaoto <inochiama@...il.com>, Bjorn Andersson <andersson@...nel.org>, 
	Mathieu Poirier <mathieu.poirier@...aro.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Chen Wang <unicorn_wang@...look.com>, Philipp Zabel <p.zabel@...gutronix.de>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>, Alexandre Ghiti <alex@...ti.fr>
Cc: linux-remoteproc@...r.kernel.org, devicetree@...r.kernel.org, 
	sophgo@...ts.linux.dev, linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v2 1/2] dt-bindings: remoteproc: Add C906L rproc for
 Sophgo CV1800B SoC

On Wed, Jul 30, 2025 at 03:57:09AM +0000, Junhui Liu wrote:
> On 29/07/2025 16:31, Inochi Amaoto wrote:
> > On Mon, Jul 28, 2025 at 07:03:23PM +0800, Junhui Liu wrote:
> >> Add C906L remote processor for CV1800B SoC, which is an asymmetric
> >> processor typically running RTOS.
> >> 
> >> Signed-off-by: Junhui Liu <junhui.liu@...moral.tech>
> >> ---
> >>  .../bindings/remoteproc/sophgo,cv1800b-c906l.yaml  | 79 ++++++++++++++++++++++
> >>  1 file changed, 79 insertions(+)
> >> 
> >> diff --git a/Documentation/devicetree/bindings/remoteproc/sophgo,cv1800b-c906l.yaml b/Documentation/devicetree/bindings/remoteproc/sophgo,cv1800b-c906l.yaml
> >> new file mode 100644
> >> index 0000000000000000000000000000000000000000..2061c2fd6ba343c09b1a91700ea4a695d2b57f81
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/remoteproc/sophgo,cv1800b-c906l.yaml
> >> @@ -0,0 +1,79 @@
> >> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> >> +%YAML 1.2
> >> +---
> >> +$id: http://devicetree.org/schemas/remoteproc/sophgo,cv1800b-c906l.yaml#
> >> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> >> +
> >> +title: Sophgo C906L remote processor controller for CV1800B SoC
> >> +
> >> +maintainers:
> >> +  - Junhui Liu <junhui.liu@...moral.tech>
> >> +
> >> +description:
> >> +  Document the bindings for the C906L remoteproc component that loads and boots
> >> +  firmwares on the CV1800B SoC.
> >> +
> >> +properties:
> >> +  compatible:
> >> +    const: sophgo,cv1800b-c906l
> >> +
> >> +  firmware-name:
> >> +    maxItems: 1
> >> +
> >> +  mbox-names:
> >> +    items:
> >> +      - const: tx
> >> +      - const: rx
> >> +
> >> +  mboxes:
> >> +    description:
> >> +      This property is required only if the rpmsg/virtio functionality is used.
> >> +      (see mailbox/sophgo,cv1800b-mailbox.yaml)
> >> +    items:
> >> +      - description: mailbox channel to send data to C906L
> >> +      - description: mailbox channel to receive data from C906L
> >> +
> >> +  memory-region:
> >> +    description:
> >> +      List of phandles to reserved memory regions used by the remote processor.
> >> +      The first region is required and provides the firmware region for the
> >> +      remote processor. The following regions (vdev buffer, vrings) are optional
> >> +      and are only required if rpmsg/virtio functionality is used.
> >> +    minItems: 1
> >> +    items:
> >> +      - description: firmware region
> >> +      - description: vdev buffer
> >> +      - description: vring0
> >> +      - description: vring1
> >> +    additionalItems: true
> >> +
> > 
> > Why not allocating these region dynamicly? I do not think firware is
> > always avaible before staring. Allowing dynamic firmware give us max
> > flexiblity.
> 
> I'm afraid it's not easy to do this.
> 
> For firmware region, the RTOS firmware usually needs a physical address
> to link to, and I have researched and tested two RTOS (RT-Thread and
> Zephyr) on the C906L, both of them do not support position-independent
> execution or runtime relocation. Therefore, a reserved memory region is
> needed to provide a fixed physical address for the RTOS firmware.

I think it is simple and possible to add PIE support for these RTOS. As
the memory of CV18XX is limited, I do not want to see some reserved
regions. This may hurt users who do not need this.

> (In fact, there is already a reserved memory region for the C906L in
> cv1800b-milkv-duo.dts)

This is just preserved for vendor zsbl and I have a plan to remove it.
Always let linux take care of all memory. It is good to support all
firmware implementation for CV18XX.

I think it is always good to use remoteproc like this:
https://www.kernel.org/doc/html/latest/staging/remoteproc.html

> 
> For virtio-related regions, the RTOS firmware also needs to know the
> shared memory regions for communications at compile time.
> 

I think you should investigate this and check if there is something you
missed. I haven't see any reserved region in remoteproc binding mentions
virtio.

Regards,
Inochi