Re: [PATCH v2 2/4] soc: qcom: rpmh: Add support to read back resource settings

[Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>]

On 10/23/25 11:46 AM, Maulik Shah (mkshah) wrote:
> 
> 
> On 10/23/2025 2:39 PM, Konrad Dybcio wrote:
>> On 10/23/25 10:57 AM, Maulik Shah (mkshah) wrote:
>>>
>>>
>>> On 10/23/2025 1:47 PM, Konrad Dybcio wrote:
>>>> On 10/23/25 6:46 AM, Maulik Shah (mkshah) wrote:
>>>>>
>>>>>
>>>>> On 10/23/2025 2:51 AM, Bjorn Andersson wrote:
>>>>>> On Wed, Oct 22, 2025 at 02:38:54AM +0530, Kamal Wadhwa wrote:
>>>>>>> From: Maulik Shah <maulik.shah@oss.qualcomm.com>
>>>>>>>
>>>>>>> All rpmh_*() APIs so far have supported placing votes for various
>>>>>>> resource settings but the H/W also have option to read resource
>>>>>>> settings.
>>>>>>>
>>>>>>> This change adds a new rpmh_read() API to allow clients
>>>>>>> to read back resource setting from H/W. This will be useful for
>>>>>>> clients like regulators, which currently don't have a way to know
>>>>>>> the settings applied during bootloader stage.
>>>>>>>
>>>>>>
>>>>>> Allow me to express my disappointment over the fact that you sat on this
>>>>>> for 7 years!
>>>>>
>>>>> This was a dead API (even in downstream) with no user since SDM845/ 7 years.
>>>>> Read support was eventually removed from downstream driver too for the same reason.
>>>>> There were early discussions to remove read support from RSC H/W, due to lack of users.
>>>>> Its not realized yet and all SoCs still supports read.
>>>>
>>>> Can we read BCM states from HLOS this way too?
>>>
>>> Yes, Any of ARC/BCM/VRM can be read to get HLOS/DRV2 votes.
>>
>> Wow this is amazing..
>>
>> Do you have code for this already, or should I hack on it?
> 
> No, it won't be of much help, as i said above it gets HLOS/DRV2 votes only for a given resource.
> More specifically, the read does not give the aggregated vote result across all the DRVs.

Hm, perhaps it could still be of *some* use

But maybe reading back rpmhpd and rpmhcc states would be of more
use!

Konrad