diff mbox series

[05/11] dt-bindings: document the Qualcomm TEE Shared Memory Bridge

Message ID 20230828192507.117334-6-bartosz.golaszewski@linaro.org
State New
Headers show
Series arm64: qcom: add and enable SHM Bridge support | expand

Commit Message

Bartosz Golaszewski Aug. 28, 2023, 7:25 p.m. UTC
Add Device Tree bindings for Qualcomm TEE Shared Memory Brige - a
mechanism that allows sharing memory buffers between trustzone and the
kernel.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
---
 .../bindings/firmware/qcom,shm-bridge.yaml    | 36 +++++++++++++++++++
 1 file changed, 36 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml

Comments

Krzysztof Kozlowski Aug. 29, 2023, 8:02 a.m. UTC | #1
On 28/08/2023 21:25, Bartosz Golaszewski wrote:
> Add Device Tree bindings for Qualcomm TEE Shared Memory Brige - a
> mechanism that allows sharing memory buffers between trustzone and the
> kernel.

Subject prefix:
dt-bindings: firmware:



> 
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> ---
>  .../bindings/firmware/qcom,shm-bridge.yaml    | 36 +++++++++++++++++++
>  1 file changed, 36 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
> 
> diff --git a/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml b/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
> new file mode 100644
> index 000000000000..f660962b7b86
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
> @@ -0,0 +1,36 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/firmware/qcom,shm-bridge.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: QCOM Shared Memory Bridge
> +
> +description: |

Do not need '|' unless you need to preserve formatting.

> +  Qualcomm TEE Shared Memory Bridge allows sharing limited areas of kernel's
> +  virtual memory with the trustzone in order to avoid mapping the entire RAM.
> +
> +maintainers:
> +  - Bjorn Andersson <andersson@kernel.org>
> +  - Konrad Dybcio <konrad.dybcio@linaro.org>
> +  - Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> +
> +properties:
> +  compatible:
> +    items:
> +      - enum:
> +          - qcom,shm-bridge-sa8775p
> +          - qcom,shm-bridge-sm8150
> +          - qcom,shm-bridge-sm8450
> +      - const: qcom,shm-bridge
> +

Looks quite empty... Why this cannot be part of qcom,scm? IOW, why do
you need new binding if you do not have any resources here and the block
is essentially feature of qcom,scm firmware?

> +required:
> +  - compatible
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    firmware {
> +         compatible = "qcom,shm-bridge-sa8775p", "qcom,shm-bridge";

Use 4 spaces for example indentation.

> +    };

Best regards,
Krzysztof
Konrad Dybcio Aug. 29, 2023, 9:30 a.m. UTC | #2
On 29.08.2023 10:02, Krzysztof Kozlowski wrote:
> On 28/08/2023 21:25, Bartosz Golaszewski wrote:
>> Add Device Tree bindings for Qualcomm TEE Shared Memory Brige - a
>> mechanism that allows sharing memory buffers between trustzone and the
>> kernel.
> 
> Subject prefix:
> dt-bindings: firmware:
> 
> 
> 
>>
>> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
>> ---
>>  .../bindings/firmware/qcom,shm-bridge.yaml    | 36 +++++++++++++++++++
>>  1 file changed, 36 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml b/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
>> new file mode 100644
>> index 000000000000..f660962b7b86
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
>> @@ -0,0 +1,36 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/firmware/qcom,shm-bridge.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: QCOM Shared Memory Bridge
>> +
>> +description: |
> 
> Do not need '|' unless you need to preserve formatting.
> 
>> +  Qualcomm TEE Shared Memory Bridge allows sharing limited areas of kernel's
>> +  virtual memory with the trustzone in order to avoid mapping the entire RAM.
>> +
>> +maintainers:
>> +  - Bjorn Andersson <andersson@kernel.org>
>> +  - Konrad Dybcio <konrad.dybcio@linaro.org>
>> +  - Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
>> +
>> +properties:
>> +  compatible:
>> +    items:
>> +      - enum:
>> +          - qcom,shm-bridge-sa8775p
>> +          - qcom,shm-bridge-sm8150
>> +          - qcom,shm-bridge-sm8450
>> +      - const: qcom,shm-bridge
>> +
> 
> Looks quite empty... Why this cannot be part of qcom,scm? IOW, why do
> you need new binding if you do not have any resources here and the block
> is essentially feature of qcom,scm firmware?
Since it's "discoverable" (via retval of an scm call), I'd second the
idea of probing this from within the SCM driver.

Konrad
Bartosz Golaszewski Aug. 30, 2023, 1:48 p.m. UTC | #3
On Tue, 29 Aug 2023 at 11:30, Konrad Dybcio <konrad.dybcio@linaro.org> wrote:
>
> On 29.08.2023 10:02, Krzysztof Kozlowski wrote:
> > On 28/08/2023 21:25, Bartosz Golaszewski wrote:
> >> Add Device Tree bindings for Qualcomm TEE Shared Memory Brige - a
> >> mechanism that allows sharing memory buffers between trustzone and the
> >> kernel.
> >
> > Subject prefix:
> > dt-bindings: firmware:
> >
> >
> >
> >>
> >> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> >> ---
> >>  .../bindings/firmware/qcom,shm-bridge.yaml    | 36 +++++++++++++++++++
> >>  1 file changed, 36 insertions(+)
> >>  create mode 100644 Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
> >>
> >> diff --git a/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml b/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
> >> new file mode 100644
> >> index 000000000000..f660962b7b86
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
> >> @@ -0,0 +1,36 @@
> >> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> >> +%YAML 1.2
> >> +---
> >> +$id: http://devicetree.org/schemas/firmware/qcom,shm-bridge.yaml#
> >> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> >> +
> >> +title: QCOM Shared Memory Bridge
> >> +
> >> +description: |
> >
> > Do not need '|' unless you need to preserve formatting.
> >
> >> +  Qualcomm TEE Shared Memory Bridge allows sharing limited areas of kernel's
> >> +  virtual memory with the trustzone in order to avoid mapping the entire RAM.
> >> +
> >> +maintainers:
> >> +  - Bjorn Andersson <andersson@kernel.org>
> >> +  - Konrad Dybcio <konrad.dybcio@linaro.org>
> >> +  - Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> >> +
> >> +properties:
> >> +  compatible:
> >> +    items:
> >> +      - enum:
> >> +          - qcom,shm-bridge-sa8775p
> >> +          - qcom,shm-bridge-sm8150
> >> +          - qcom,shm-bridge-sm8450
> >> +      - const: qcom,shm-bridge
> >> +
> >
> > Looks quite empty... Why this cannot be part of qcom,scm? IOW, why do
> > you need new binding if you do not have any resources here and the block
> > is essentially feature of qcom,scm firmware?
> Since it's "discoverable" (via retval of an scm call), I'd second the
> idea of probing this from within the SCM driver.
>
> Konrad

Downstream has a bunch of DT switches that we don't support for now
upstream. I disagree about shoehorning this into the SCM driver. It
really is a layer on top of SCM but also SCM is a user of this
interface.

I will send a v2 with QCom ICE as a second user so that exporting
symbols pointed out by Krzysztof as having no users make more sense.
Hopefully keeping it separate will make more sense too.

If anything, the SHM Bridge code should stay in a separate compilation
unit even as part of SCM.

Bart
Krzysztof Kozlowski Aug. 30, 2023, 2:31 p.m. UTC | #4
On 30/08/2023 15:48, Bartosz Golaszewski wrote:
> On Tue, 29 Aug 2023 at 11:30, Konrad Dybcio <konrad.dybcio@linaro.org> wrote:
>>
>> On 29.08.2023 10:02, Krzysztof Kozlowski wrote:
>>> On 28/08/2023 21:25, Bartosz Golaszewski wrote:
>>>> Add Device Tree bindings for Qualcomm TEE Shared Memory Brige - a
>>>> mechanism that allows sharing memory buffers between trustzone and the
>>>> kernel.
>>>
>>> Subject prefix:
>>> dt-bindings: firmware:
>>>
>>>
>>>
>>>>
>>>> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
>>>> ---
>>>>  .../bindings/firmware/qcom,shm-bridge.yaml    | 36 +++++++++++++++++++
>>>>  1 file changed, 36 insertions(+)
>>>>  create mode 100644 Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml b/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
>>>> new file mode 100644
>>>> index 000000000000..f660962b7b86
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
>>>> @@ -0,0 +1,36 @@
>>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>>> +%YAML 1.2
>>>> +---
>>>> +$id: http://devicetree.org/schemas/firmware/qcom,shm-bridge.yaml#
>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>>> +
>>>> +title: QCOM Shared Memory Bridge
>>>> +
>>>> +description: |
>>>
>>> Do not need '|' unless you need to preserve formatting.
>>>
>>>> +  Qualcomm TEE Shared Memory Bridge allows sharing limited areas of kernel's
>>>> +  virtual memory with the trustzone in order to avoid mapping the entire RAM.
>>>> +
>>>> +maintainers:
>>>> +  - Bjorn Andersson <andersson@kernel.org>
>>>> +  - Konrad Dybcio <konrad.dybcio@linaro.org>
>>>> +  - Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
>>>> +
>>>> +properties:
>>>> +  compatible:
>>>> +    items:
>>>> +      - enum:
>>>> +          - qcom,shm-bridge-sa8775p
>>>> +          - qcom,shm-bridge-sm8150
>>>> +          - qcom,shm-bridge-sm8450
>>>> +      - const: qcom,shm-bridge
>>>> +
>>>
>>> Looks quite empty... Why this cannot be part of qcom,scm? IOW, why do
>>> you need new binding if you do not have any resources here and the block
>>> is essentially feature of qcom,scm firmware?
>> Since it's "discoverable" (via retval of an scm call), I'd second the
>> idea of probing this from within the SCM driver.
>>
>> Konrad
> 
> Downstream has a bunch of DT switches that we don't support for now
> upstream. I disagree about shoehorning this into the SCM driver. It
> really is a layer on top of SCM but also SCM is a user of this
> interface.

Sure, for the driver makes sense, but it does not really explain why DT
node is needed. It is not separate hardware. I doubt it is even separate
firmware, but part of SCM.

Best regards,
Krzysztof
Bartosz Golaszewski Aug. 30, 2023, 2:39 p.m. UTC | #5
On Wed, 30 Aug 2023 at 16:31, Krzysztof Kozlowski
<krzysztof.kozlowski@linaro.org> wrote:
>
> On 30/08/2023 15:48, Bartosz Golaszewski wrote:
> > On Tue, 29 Aug 2023 at 11:30, Konrad Dybcio <konrad.dybcio@linaro.org> wrote:
> >>
> >> On 29.08.2023 10:02, Krzysztof Kozlowski wrote:
> >>> On 28/08/2023 21:25, Bartosz Golaszewski wrote:
> >>>> Add Device Tree bindings for Qualcomm TEE Shared Memory Brige - a
> >>>> mechanism that allows sharing memory buffers between trustzone and the
> >>>> kernel.
> >>>
> >>> Subject prefix:
> >>> dt-bindings: firmware:
> >>>
> >>>
> >>>
> >>>>
> >>>> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> >>>> ---
> >>>>  .../bindings/firmware/qcom,shm-bridge.yaml    | 36 +++++++++++++++++++
> >>>>  1 file changed, 36 insertions(+)
> >>>>  create mode 100644 Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
> >>>>
> >>>> diff --git a/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml b/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
> >>>> new file mode 100644
> >>>> index 000000000000..f660962b7b86
> >>>> --- /dev/null
> >>>> +++ b/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
> >>>> @@ -0,0 +1,36 @@
> >>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> >>>> +%YAML 1.2
> >>>> +---
> >>>> +$id: http://devicetree.org/schemas/firmware/qcom,shm-bridge.yaml#
> >>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> >>>> +
> >>>> +title: QCOM Shared Memory Bridge
> >>>> +
> >>>> +description: |
> >>>
> >>> Do not need '|' unless you need to preserve formatting.
> >>>
> >>>> +  Qualcomm TEE Shared Memory Bridge allows sharing limited areas of kernel's
> >>>> +  virtual memory with the trustzone in order to avoid mapping the entire RAM.
> >>>> +
> >>>> +maintainers:
> >>>> +  - Bjorn Andersson <andersson@kernel.org>
> >>>> +  - Konrad Dybcio <konrad.dybcio@linaro.org>
> >>>> +  - Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> >>>> +
> >>>> +properties:
> >>>> +  compatible:
> >>>> +    items:
> >>>> +      - enum:
> >>>> +          - qcom,shm-bridge-sa8775p
> >>>> +          - qcom,shm-bridge-sm8150
> >>>> +          - qcom,shm-bridge-sm8450
> >>>> +      - const: qcom,shm-bridge
> >>>> +
> >>>
> >>> Looks quite empty... Why this cannot be part of qcom,scm? IOW, why do
> >>> you need new binding if you do not have any resources here and the block
> >>> is essentially feature of qcom,scm firmware?
> >> Since it's "discoverable" (via retval of an scm call), I'd second the
> >> idea of probing this from within the SCM driver.
> >>
> >> Konrad
> >
> > Downstream has a bunch of DT switches that we don't support for now
> > upstream. I disagree about shoehorning this into the SCM driver. It
> > really is a layer on top of SCM but also SCM is a user of this
> > interface.
>
> Sure, for the driver makes sense, but it does not really explain why DT
> node is needed. It is not separate hardware. I doubt it is even separate
> firmware, but part of SCM.
>
> Best regards,
> Krzysztof
>

Because not all platforms support it and it's the simplest way of
marking the ones that do. Both SHM and SCM nodes sit on the firmware
node anyway. What do you recommend? A property of the SCM node? Like
'qcom,shm-bridge` or something?

Bart
Krzysztof Kozlowski Aug. 30, 2023, 2:58 p.m. UTC | #6
On 30/08/2023 16:39, Bartosz Golaszewski wrote:
> On Wed, 30 Aug 2023 at 16:31, Krzysztof Kozlowski
> <krzysztof.kozlowski@linaro.org> wrote:
>>
>> On 30/08/2023 15:48, Bartosz Golaszewski wrote:
>>> On Tue, 29 Aug 2023 at 11:30, Konrad Dybcio <konrad.dybcio@linaro.org> wrote:
>>>>
>>>> On 29.08.2023 10:02, Krzysztof Kozlowski wrote:
>>>>> On 28/08/2023 21:25, Bartosz Golaszewski wrote:
>>>>>> Add Device Tree bindings for Qualcomm TEE Shared Memory Brige - a
>>>>>> mechanism that allows sharing memory buffers between trustzone and the
>>>>>> kernel.
>>>>>
>>>>> Subject prefix:
>>>>> dt-bindings: firmware:
>>>>>
>>>>>
>>>>>
>>>>>>
>>>>>> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
>>>>>> ---
>>>>>>  .../bindings/firmware/qcom,shm-bridge.yaml    | 36 +++++++++++++++++++
>>>>>>  1 file changed, 36 insertions(+)
>>>>>>  create mode 100644 Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
>>>>>>
>>>>>> diff --git a/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml b/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
>>>>>> new file mode 100644
>>>>>> index 000000000000..f660962b7b86
>>>>>> --- /dev/null
>>>>>> +++ b/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
>>>>>> @@ -0,0 +1,36 @@
>>>>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>>>>> +%YAML 1.2
>>>>>> +---
>>>>>> +$id: http://devicetree.org/schemas/firmware/qcom,shm-bridge.yaml#
>>>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>>>>> +
>>>>>> +title: QCOM Shared Memory Bridge
>>>>>> +
>>>>>> +description: |
>>>>>
>>>>> Do not need '|' unless you need to preserve formatting.
>>>>>
>>>>>> +  Qualcomm TEE Shared Memory Bridge allows sharing limited areas of kernel's
>>>>>> +  virtual memory with the trustzone in order to avoid mapping the entire RAM.
>>>>>> +
>>>>>> +maintainers:
>>>>>> +  - Bjorn Andersson <andersson@kernel.org>
>>>>>> +  - Konrad Dybcio <konrad.dybcio@linaro.org>
>>>>>> +  - Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
>>>>>> +
>>>>>> +properties:
>>>>>> +  compatible:
>>>>>> +    items:
>>>>>> +      - enum:
>>>>>> +          - qcom,shm-bridge-sa8775p
>>>>>> +          - qcom,shm-bridge-sm8150
>>>>>> +          - qcom,shm-bridge-sm8450
>>>>>> +      - const: qcom,shm-bridge
>>>>>> +
>>>>>
>>>>> Looks quite empty... Why this cannot be part of qcom,scm? IOW, why do
>>>>> you need new binding if you do not have any resources here and the block
>>>>> is essentially feature of qcom,scm firmware?
>>>> Since it's "discoverable" (via retval of an scm call), I'd second the
>>>> idea of probing this from within the SCM driver.
>>>>
>>>> Konrad
>>>
>>> Downstream has a bunch of DT switches that we don't support for now
>>> upstream. I disagree about shoehorning this into the SCM driver. It
>>> really is a layer on top of SCM but also SCM is a user of this
>>> interface.
>>
>> Sure, for the driver makes sense, but it does not really explain why DT
>> node is needed. It is not separate hardware. I doubt it is even separate
>> firmware, but part of SCM.
>>
>> Best regards,
>> Krzysztof
>>
> 
> Because not all platforms support it and it's the simplest way of

Platforms like SoCs or boards?

> marking the ones that do. Both SHM and SCM nodes sit on the firmware
> node anyway. What do you recommend? A property of the SCM node? Like
> 'qcom,shm-bridge` or something?

If the first - you talk about SoCs - then you have everything needed
already: SCM compatibles. This defines it fully.

If it varies by boards with one SoC, would be different case, but I
really doubt it.

Best regards,
Krzysztof
Bartosz Golaszewski Aug. 30, 2023, 4:21 p.m. UTC | #7
On Wed, 30 Aug 2023 at 16:58, Krzysztof Kozlowski
<krzysztof.kozlowski@linaro.org> wrote:
>
> On 30/08/2023 16:39, Bartosz Golaszewski wrote:
> > On Wed, 30 Aug 2023 at 16:31, Krzysztof Kozlowski
> > <krzysztof.kozlowski@linaro.org> wrote:
> >>
> >> On 30/08/2023 15:48, Bartosz Golaszewski wrote:
> >>> On Tue, 29 Aug 2023 at 11:30, Konrad Dybcio <konrad.dybcio@linaro.org> wrote:
> >>>>
> >>>> On 29.08.2023 10:02, Krzysztof Kozlowski wrote:
> >>>>> On 28/08/2023 21:25, Bartosz Golaszewski wrote:
> >>>>>> Add Device Tree bindings for Qualcomm TEE Shared Memory Brige - a
> >>>>>> mechanism that allows sharing memory buffers between trustzone and the
> >>>>>> kernel.
> >>>>>
> >>>>> Subject prefix:
> >>>>> dt-bindings: firmware:
> >>>>>
> >>>>>
> >>>>>
> >>>>>>
> >>>>>> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> >>>>>> ---
> >>>>>>  .../bindings/firmware/qcom,shm-bridge.yaml    | 36 +++++++++++++++++++
> >>>>>>  1 file changed, 36 insertions(+)
> >>>>>>  create mode 100644 Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
> >>>>>>
> >>>>>> diff --git a/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml b/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
> >>>>>> new file mode 100644
> >>>>>> index 000000000000..f660962b7b86
> >>>>>> --- /dev/null
> >>>>>> +++ b/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
> >>>>>> @@ -0,0 +1,36 @@
> >>>>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> >>>>>> +%YAML 1.2
> >>>>>> +---
> >>>>>> +$id: http://devicetree.org/schemas/firmware/qcom,shm-bridge.yaml#
> >>>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> >>>>>> +
> >>>>>> +title: QCOM Shared Memory Bridge
> >>>>>> +
> >>>>>> +description: |
> >>>>>
> >>>>> Do not need '|' unless you need to preserve formatting.
> >>>>>
> >>>>>> +  Qualcomm TEE Shared Memory Bridge allows sharing limited areas of kernel's
> >>>>>> +  virtual memory with the trustzone in order to avoid mapping the entire RAM.
> >>>>>> +
> >>>>>> +maintainers:
> >>>>>> +  - Bjorn Andersson <andersson@kernel.org>
> >>>>>> +  - Konrad Dybcio <konrad.dybcio@linaro.org>
> >>>>>> +  - Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> >>>>>> +
> >>>>>> +properties:
> >>>>>> +  compatible:
> >>>>>> +    items:
> >>>>>> +      - enum:
> >>>>>> +          - qcom,shm-bridge-sa8775p
> >>>>>> +          - qcom,shm-bridge-sm8150
> >>>>>> +          - qcom,shm-bridge-sm8450
> >>>>>> +      - const: qcom,shm-bridge
> >>>>>> +
> >>>>>
> >>>>> Looks quite empty... Why this cannot be part of qcom,scm? IOW, why do
> >>>>> you need new binding if you do not have any resources here and the block
> >>>>> is essentially feature of qcom,scm firmware?
> >>>> Since it's "discoverable" (via retval of an scm call), I'd second the
> >>>> idea of probing this from within the SCM driver.
> >>>>
> >>>> Konrad
> >>>
> >>> Downstream has a bunch of DT switches that we don't support for now
> >>> upstream. I disagree about shoehorning this into the SCM driver. It
> >>> really is a layer on top of SCM but also SCM is a user of this
> >>> interface.
> >>
> >> Sure, for the driver makes sense, but it does not really explain why DT
> >> node is needed. It is not separate hardware. I doubt it is even separate
> >> firmware, but part of SCM.
> >>
> >> Best regards,
> >> Krzysztof
> >>
> >
> > Because not all platforms support it and it's the simplest way of
>
> Platforms like SoCs or boards?
>
> > marking the ones that do. Both SHM and SCM nodes sit on the firmware
> > node anyway. What do you recommend? A property of the SCM node? Like
> > 'qcom,shm-bridge` or something?
>
> If the first - you talk about SoCs - then you have everything needed
> already: SCM compatibles. This defines it fully.
>
> If it varies by boards with one SoC, would be different case, but I
> really doubt it.
>

Ok, makes sense. Thanks.

Bartosz
diff mbox series

Patch

diff --git a/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml b/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
new file mode 100644
index 000000000000..f660962b7b86
--- /dev/null
+++ b/Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
@@ -0,0 +1,36 @@ 
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/firmware/qcom,shm-bridge.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: QCOM Shared Memory Bridge
+
+description: |
+  Qualcomm TEE Shared Memory Bridge allows sharing limited areas of kernel's
+  virtual memory with the trustzone in order to avoid mapping the entire RAM.
+
+maintainers:
+  - Bjorn Andersson <andersson@kernel.org>
+  - Konrad Dybcio <konrad.dybcio@linaro.org>
+  - Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
+
+properties:
+  compatible:
+    items:
+      - enum:
+          - qcom,shm-bridge-sa8775p
+          - qcom,shm-bridge-sm8150
+          - qcom,shm-bridge-sm8450
+      - const: qcom,shm-bridge
+
+required:
+  - compatible
+
+additionalProperties: false
+
+examples:
+  - |
+    firmware {
+         compatible = "qcom,shm-bridge-sa8775p", "qcom,shm-bridge";
+    };