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

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Message-ID: <litd6qcxuios7uwwcrz55ea24kj26onrjo2aekouynsce6wslj@vatjbulg64mb>
Date: Wed, 22 Oct 2025 16:21:08 -0500
From: Bjorn Andersson <andersson@...nel.org>
To: Kamal Wadhwa <kamal.wadhwa@....qualcomm.com>
Cc: Konrad Dybcio <konradybcio@...nel.org>, 
	Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>, linux-arm-msm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Maulik Shah <maulik.shah@....qualcomm.com>
Subject: Re: [PATCH v2 2/4] soc: qcom: rpmh: Add support to read back
 resource settings

On Wed, Oct 22, 2025 at 02:38:54AM +0530, 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.
> 

Allow me to express my disappointment over the fact that you sat on this
for 7 years!

> Link: https://lore.kernel.org/r/20250623-add-rpmh-read-support-v1-1-ae583d260195@oss.qualcomm.com

Why is there a Link here?

> Signed-off-by: Maulik Shah <maulik.shah@....qualcomm.com>
> Signed-off-by: Kamal Wadhwa <kamal.wadhwa@....qualcomm.com>
> ---
>  drivers/soc/qcom/rpmh-rsc.c | 13 +++++++++++--
>  drivers/soc/qcom/rpmh.c     | 47 +++++++++++++++++++++++++++++++++++++++++----
>  include/soc/qcom/rpmh.h     |  5 +++++
>  include/soc/qcom/tcs.h      |  2 ++
>  4 files changed, 61 insertions(+), 6 deletions(-)
> 
[..]
> diff --git a/drivers/soc/qcom/rpmh.c b/drivers/soc/qcom/rpmh.c
[..]
> +/**
> + * rpmh_read: Read a resource value
> + *
> + * @dev: The device making the request
> + * @cmd: The payload having address of resource to read
> + *
> + * Reads the value for the resource address given in tcs_cmd->addr
> + * and returns the tcs_cmd->data filled with same.
> + *
> + * May sleep. Do not call from atomic contexts.

* Context: May sleep...

Regards,
Bjorn

> + *
> + * Return: 0 on success, negative errno on failure
> + */
> +int rpmh_read(const struct device *dev, struct tcs_cmd *cmd)