Re: [PATCH] arm64: dts: qcom: sa8775p: fix the secure device bootup issue

[Jie Gan <quic_jiegan@quicinc.com>]

On 12/23/2024 7:56 PM, Konrad Dybcio wrote:
> On 20.12.2024 6:51 AM, Jie Gan wrote:
>>
>>
>> On 12/20/2024 5:25 AM, Konrad Dybcio wrote:
>>> On 19.12.2024 3:52 AM, Jie Gan wrote:
>>>> The secure device(fused) cannot bootup with TPDM_DCC device. So
>>>> disable it in DT.
>>>>
>>>> Fixes: 6596118ccdcd ("arm64: dts: qcom: Add coresight nodes for SA8775p")
>>>> Signed-off-by: Jie Gan <quic_jiegan@quicinc.com>
>>>> ---
>>>
>>> I was thinking, is there a QFPROM fuse we could read on both
>>> secure and non-secure devices to determine whether all coresight
>>> components will be accessible, and enable them based on that
>>> information?
>>>
>> There are two known TPDM devices had been disabled on secure device. One of these devices is TPDM_DCC. In downstream code, we have an API to check the secure status of the device in TPDM's probe function, to avoid unintentional enable. The downstream API will check the register that controls crash dump functionality in TZ and the crash dump functionality is disabled by default on secure devices.
> 
> That's an "eeeh" type solution, crashdump is a separate thing that may be
> enabled independently, and some prod devices from certain vendors actually
> do that
> 
This solution have been applied because the TPDM_DCC has connection with 
crashdump. But I think you are right, this is not a totally suitable 
solution.


>> We need to verify if the downstream API is supported by the upstream kernel. We plan to upstream a patch to implement this functionality in the TPDM driver or any other device's driver that needed the functionality.
> 
> Please check if there's a coresight-specific fuse instead
I will check it with hardware team.

> 
> 
>> For the time being, we need to disable this TPDM device in DT because the TPDM_DCC will break the bootup process on secure devices.
> 
> Yeah, right
> 
> Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
> 
> Konrad

Thanks,
Jie