linux-kernel - Re: [PATCH V2 4/6] regulator: qcom_smd: Add support to define the bootup voltage

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Date:   Wed, 22 Feb 2023 23:11:42 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Devi Priya <quic_devipriy@...cinc.com>, agross@...nel.org,
        andersson@...nel.org, lgirdwood@...il.com, broonie@...nel.org,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Cc:     quic_srichara@...cinc.com, quic_gokulsri@...cinc.com,
        quic_sjaganat@...cinc.com, quic_kathirav@...cinc.com,
        quic_arajkuma@...cinc.com, quic_anusha@...cinc.com,
        quic_ipkumar@...cinc.com
Subject: Re: [PATCH V2 4/6] regulator: qcom_smd: Add support to define the
 bootup voltage



On 17.02.2023 15:20, Devi Priya wrote:
> Kernel does not know the initial voltage set by the bootloaders.
> During regulator registration, the voltage variable is just declared
> and it is zero. Based on that, the regulator framework considers current
> the voltage as zero and tries to bring up each regulator to minimum
> the supported voltage.
> 
> This introduces a dip in the voltage during kernel boot and gets
> stabilized once the voltage scaling comes into picture.
> 
> To avoid the voltage dip, adding support to define the
> bootup voltage set by the boodloaders and based on it, regulator
> framework understands that proper voltage is already set
> 
> Co-developed-by: Praveenkumar I <quic_ipkumar@...cinc.com>
> Signed-off-by: Praveenkumar I <quic_ipkumar@...cinc.com>
> Signed-off-by: Devi Priya <quic_devipriy@...cinc.com>
> ---
Thinking about it again, this seems like something that could be
generalized and introduced into regulator core.. Hardcoding this
will not end well.. Not to mention it'll affect all mp5496-using
boards that are already upstream.

WDYT about regulator-init-microvolts Mark?

Konrad
>  Changes in V2:
> 	- Added the bootup voltages to s2 and l2 regulators
> 
>  drivers/regulator/qcom_smd-regulator.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/regulator/qcom_smd-regulator.c b/drivers/regulator/qcom_smd-regulator.c
> index a40e66cea7e7..5f9fe6b9d368 100644
> --- a/drivers/regulator/qcom_smd-regulator.c
> +++ b/drivers/regulator/qcom_smd-regulator.c
> @@ -800,12 +800,13 @@ struct rpm_regulator_data {
>  	u32 id;
>  	const struct regulator_desc *desc;
>  	const char *supply;
> +	int boot_uV; /* To store the bootup voltage set by bootloaders */
>  };
>  
>  static const struct rpm_regulator_data rpm_mp5496_regulators[] = {
> -	{ "s1", QCOM_SMD_RPM_SMPA, 1, &mp5496_smpa1, "s1" },
> -	{ "s2", QCOM_SMD_RPM_SMPA, 2, &mp5496_smpa2, "s2" },
> -	{ "l2", QCOM_SMD_RPM_LDOA, 2, &mp5496_ldoa2, "l2" },
> +	{ "s1", QCOM_SMD_RPM_SMPA, 1, &mp5496_smpa1, "s1", 875000  },
> +	{ "s2", QCOM_SMD_RPM_SMPA, 2, &mp5496_smpa2, "s2", 875000  },
> +	{ "l2", QCOM_SMD_RPM_LDOA, 2, &mp5496_ldoa2, "l2", 2950000 },
>  	{}
>  };
>  
> @@ -1388,6 +1389,9 @@ static int rpm_regulator_init_vreg(struct qcom_rpm_reg *vreg, struct device *dev
>  	vreg->type	= rpm_data->type;
>  	vreg->id	= rpm_data->id;
>  
> +	if (rpm_data->boot_uV)
> +		vreg->uV = rpm_data->boot_uV;
> +
>  	memcpy(&vreg->desc, rpm_data->desc, sizeof(vreg->desc));
>  	vreg->desc.name = rpm_data->name;
>  	vreg->desc.supply_name = rpm_data->supply;