linux-kernel - Re: [PATCH v1 1/3] dt-bindings: soc: qcom: eud: Update compatible strings for eud

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Message-ID: <0eca6755-a2ec-404f-b98c-ee6c9f6fb55f@gmail.com>
Date: Wed, 14 Aug 2024 22:25:50 +0200
From: Konrad Dybcio <konradybcio@...il.com>
To: Melody Olvera <quic_molvera@...cinc.com>,
 Konrad Dybcio <konradybcio@...nel.org>, Krzysztof Kozlowski
 <krzk@...nel.org>, Souradeep Chowdhury <quic_schowdhu@...cinc.com>,
 Bjorn Andersson <andersson@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Trilok Soni <quic_tsoni@...cinc.com>,
 Satya Durga Srinivasu Prabhala <quic_satyap@...cinc.com>,
 Elson Serrao <quic_eserrao@...cinc.com>
Cc: cros-qcom-dts-watchers@...omium.org, linux-arm-msm@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-usb@...r.kernel.org
Subject: Re: [PATCH v1 1/3] dt-bindings: soc: qcom: eud: Update compatible
 strings for eud

On 14.08.2024 7:33 PM, Melody Olvera wrote:
> 
> 
> On 8/14/2024 3:30 AM, Konrad Dybcio wrote:
>> On 14.08.2024 8:15 AM, Krzysztof Kozlowski wrote:
>>> On 13/08/2024 22:03, Melody Olvera wrote:
>>>>
>>>> On 8/8/2024 4:00 AM, Krzysztof Kozlowski wrote:
>>>>> On 07/08/2024 20:32, Melody Olvera wrote:
>>>>>> The EUD can more accurately be divided into two types; a secure type
>>>>>> which requires that certain registers be updated via scm call and a
>>>>>> nonsecure type which must access registers nonsecurely. Thus, change
>>>>>> the compatible strings to reflect secure and nonsecure eud usage.
>>>>>>
>>>>>> Signed-off-by: Melody Olvera <quic_molvera@...cinc.com>
>>>>>> ---
>>>>>>    Documentation/devicetree/bindings/soc/qcom/qcom,eud.yaml | 6 +++---
>>>>>>    1 file changed, 3 insertions(+), 3 deletions(-)
>>>>>>
>>>>>> diff --git a/Documentation/devicetree/bindings/soc/qcom/qcom,eud.yaml b/Documentation/devicetree/bindings/soc/qcom/qcom,eud.yaml
>>>>>> index f2c5ec7e6437..476f92768610 100644
>>>>>> --- a/Documentation/devicetree/bindings/soc/qcom/qcom,eud.yaml
>>>>>> +++ b/Documentation/devicetree/bindings/soc/qcom/qcom,eud.yaml
>>>>>> @@ -17,8 +17,8 @@ properties:
>>>>>>      compatible:
>>>>>>        items:
>>>>>>          - enum:
>>>>>> -          - qcom,sc7280-eud
>>>>>> -      - const: qcom,eud
>>>>>> +          - qcom,secure-eud
>>>>>> +          - qcom,eud
>>>>> Commit msg did not explain me why DT bindings rules are avoided here and
>>>>> you drop existing SoC specific compatible.
>>>>>
>>>>> This really does not look like having any sense at all, I cannot come up
>>>>> with logic behind dropping existing users. You could deprecate it, but
>>>>> then why exactly this device should have exception from generic bindings
>>>>> rule?
>>>> Understood. I won't drop this compatible string. Is alright to add the
>>>> additional compatible as is?
>>> You always need SoC specific compatible.
>> Melody, is there any way to discover (that won't crash the board if we
>> guess wrong) whether secure accessors are needed?
>>
> 
> Unfortunately, no. We considered several options, but none guarantee that we will avoid
> a crash if we try non-securely. The secure call also won't give a specific error if it fails either
> (for security reasons) so we can't know if a secure access failed because it's supposed to be
> accessed non-securely or for another reason; hence this approach. If there's
> another way to achieve this functionality that might be better, I'm all ears.

Can we read some fuse values and decide based on that?

Konrad