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

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Message-ID: <8bb412f8-4fe1-40ca-8414-bb77c66899ae@quicinc.com>
Date: Wed, 14 Aug 2024 10:33:33 -0700
From: Melody Olvera <quic_molvera@...cinc.com>
To: 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 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.

Thanks,
Melody