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

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Message-ID: <5029600e-a3b8-4aec-a374-526fb3f6417e@oss.qualcomm.com>
Date: Mon, 17 Nov 2025 13:56:47 +0530
From: "Maulik Shah (mkshah)" <maulik.shah@....qualcomm.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        Kamal Wadhwa <kamal.wadhwa@....qualcomm.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/4] soc: qcom: rpmh: Add support to read back resource
 settings



On 11/12/2025 4:56 PM, Konrad Dybcio wrote:
> On 10/21/25 11:08 PM, Kamal Wadhwa wrote:
>> From: Maulik Shah <maulik.shah@....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.
>>
>> Link: https://lore.kernel.org/r/20250623-add-rpmh-read-support-v1-1-ae583d260195@oss.qualcomm.com
>> Signed-off-by: Maulik Shah <maulik.shah@....qualcomm.com>
>> Signed-off-by: Kamal Wadhwa <kamal.wadhwa@....qualcomm.com>
>> ---
> 
> [...]
> 
>> +int rpmh_read(const struct device *dev, struct tcs_cmd *cmd)
>> +{
>> +	DECLARE_COMPLETION_ONSTACK(compl);
>> +	DEFINE_RPMH_MSG_ONSTACK(dev, RPMH_ACTIVE_ONLY_STATE, &compl, rpm_msg);
>> +	int ret;
>> +
>> +	ret = __fill_rpmh_msg(&rpm_msg, RPMH_ACTIVE_ONLY_STATE, cmd, 1, true);
>> +	if (ret)
>> +		return ret;
>> +
>> +	ret = __rpmh_write(dev, RPMH_ACTIVE_ONLY_STATE, &rpm_msg);
> 
> Is there a reason for making this ACTIVE_ONLY?

Yes, using ACTIVE_ONLY makes the read request place immediately to read back the current resource setting.
Sleep/Wake are H/W based trigger and are not applicable for this API.

Thanks,
Maulik